Impact of Research on the Evolution of Accessibility Standards

Abstract

Accessibility in the built environment is crucial for achieving the Sustainable Development Goals (SDGs) to promote equity, inclusion, and sustainable urban development. This study examines how the quantity and content of research on the accessibility of built environments for people with physical, sensory, and cognitive/intellectual disabilities impacted the development of accessibility standards. A systematic review was conducted to investigate the correlation between standard evolution and pertinent research. A representative sample was selected and reviewed to identify connections between research and the development of standards and to highlight gaps and limitations that hinder comprehensive accessibility standards. Canada’s CSA/ASC B651 standard is used as a case study. The study revealed that the evolution of the standard is constrained by the status and type of research. Results indicated that 50% of the research reviewed focuses on individuals with physical disabilities, half of the studies are not data-driven, and most research on people with cognitive or intellectual disabilities follows medical models, with data that are not suitable for standard development.

1. Introduction

People with disabilities constitute a vital segment of human diversity. As of 2021, approximately 1.3 billion people, accounting for 16% of the world’s population, live with some form of disability [1]. Article 9 of the United Nations Convention on the Rights of Persons with Disabilities (CRPD) established moral and ethical obligations to create accessible built environments that enable all individuals to live independently and participate fully in all aspects [2]. This necessitated the development of accessibility standards in alignment with the CRPD’s goals. Additionally, ensuring accessibility in the built environment is a vital step towards achieving the Sustainable Development Goals (SDGs), particularly “SDG 10: Reduced inequalities” and “SDG 11: Sustainable cities and communities” [3,4,5].

Since their inception, accessibility standards have predominantly aimed to ensure physical environments and public spaces are usable by all individuals, including those with disabilities. Initially, the emphasis was on eliminating “physical barriers” by providing accessible entrances and circulation routes, often with limited attention to sensory or communication barriers [6,7,8]. Over time, the diverse needs of people with disabilities, coupled with the impact of social and economic factors, have driven the demand for research to support the advancement of accessibility standards. As a result, the needs of people with disabilities started expanding, with numerous studies focusing on designing inclusive environments, developing accessible features, assessing the thoroughness and effectiveness of accessibility standards, and understanding the needs and perspectives of people with disabilities. Despite the abundance of available research, the extent and significance of their findings vary substantially. This study aims to examine the current state of research on accessibility in built environments, identifies potential gaps and limitations, and highlights the corresponding impact on the progress of accessibility standards.

2. Methodology

A systematic review was conducted to investigate the relationship between the evolution/state of completeness of accessibility standards and peer-reviewed accessibility research studies. The Web of Science and Google Scholar databases were the main source for collecting papers. The initial search criteria included (1) peer-reviewed journals and conference papers published from 1980 on, (2) papers containing accessibility in either the keywords or title, and (3) papers containing one or more of the following terms as keywords: “built environment”, “disability”, “physical”, “sensory”, “hearing”, “vision”, “cognitive/intellectual”. The research, which began in mid-2020 and ended at the end of 2024, yielded 104 papers. Subsequently, the papers underwent two screening rounds. In the first round, the papers that studied the medical and/or social aspects of accessibility were considered outside the scope of this study due to their limited engineering content and therefore were excluded. Accordingly, a total of 40 papers were excluded. For the second round, the exclusion criteria included papers that contain outdated and/or repetitive information especially those that focus on auditing the “overall accessibility” of built environments. These screenings resulted in 52 papers meeting the inclusion criteria. The papers were then divided into four groups representing the people with physical, vision, hearing, and cognitive/intellectual disabilities as shown in Figure 1. To further reduce trivial repetitions, a representative sample was then selected and reviewed qualitatively by noting the date and method of research, sample size and composition, analysis method, and findings, and quantitatively by counting their corresponding numbers. The Canadian Accessibility Standard (CSA/ASC B651—Accessible Design for the Built Environment) was employed as a case study to investigate the impact of research on the standard’s evolution [9,10,11,12,13,14]. Comparative analyses were carried out to determine the relationships between the development state of the standard and research pertaining to each type of disability.

3. Status of Research Pertaining to Physical Disabilities

Over the last few decades, accessibility of built environments for people with physical disabilities has been a predominant subject of research worldwide. Researchers have explored the interaction between individuals with physical disabilities and various aspects of their environments. Most of the past research, along with only a few recent studies, has concentrated on evaluating how well accessibility standards addressed specific features and elements, such as area allowances to accommodate users with wheelchairs, dimensions and requirements for ramps and curb ramps, specifications of floor surfaces, navigation and wayfinding strategies, evacuation procedures during emergencies, etc. On the other hand, most research focused on evaluating the overall accessibility of the built environments rather than assessing specific features and elements.

3.1. Specific Accessibility Features

People with mobility impairments require adequate space to navigate public spaces and facilities freely, safely, and independently without barriers. As such, research assessed the minimum space dimensions needed to accommodate users maneuvering with wheelchairs based on anthropometric data and the varying needs and abilities. Studies in this field were found to be limited and dated. Dutta et al. investigated the minimum space required for scooters to navigate various spatial arrangements created using free-standing Styrofoam walls [15]. Five different scooter models were tested by an expert driver who entered, performed a three-point turn, and exited the configuration. The dimensions were reduced until the driver could no longer perform the maneuver. All five scooters were found to fail to maneuver within the space recommended by the Canadian and US standards at the time of the experiment. Despite its significance, the experiment was conducted by an expert driver without lived experience with disability, and only specific scooter models in good condition and high performance were used. In a subsequent study, the minimum room dimensions were determined for a scooter to complete a three-point turn, as the standard at the time of the experiment accommodated only manual wheelchairs [16]. Two four-wheeled scooters were tested in rectangular rooms with varying aspect ratios. The results revealed the need to increase the dimensions of the tested rooms by about 53% and 223% compared to the floor space recommended by the US and Canadian standards at that time.

Another pilot study in Québec, Canada, proposed an approach for measuring the maneuvering area required for manual or powered wheelchairs in a washroom facility [17]. Eight participants with varying abilities and speeds, utilizing manual and powered wheelchairs, were recruited through a rehabilitation institute. A simulated washroom facility was constructed with three different setups. An optical motion capture system tracked the 3D movement of the participants in wheelchairs. The study revealed that an additional 100 and 300 mm is required for comfortable maneuvering of manual and powered wheelchairs, respectively, more than the minimum 1500 × 1500 mm area recommended by building code and accessibility standards. Additionally, the space required to complete an extensive maneuver needed to be elliptical, not circular, as suggested by most codes. The study was conducted with a small sample size and a specific washroom setup.

Other research studies explored specific features within access routes, particularly ramps and curb ramps. For instance, a study investigated different ramp slopes recommended by the Americans with Disabilities Act Accessibility Guidelines (ADAAG) in 1997 [18]. An experimental setup consisting of a 30-ft aluminum ramp with adjustable slopes ranging from 1:20 to 1:8 was constructed and tested at a lobby space of a former hotel by 171 participants with varying mobility impairments and assistive aids. The participants were selected through a sample frame representative of the population, matched via a universal design advisory network database. Telephone inquiries were also made to local disability practitioners, and flyers and newspaper advertisements were distributed to assist during the recruitment process. The participants were instructed to navigate the ramp and rate the difficulty of each slope while monitoring their performance times and physiological characteristics, including pulse and oxygen saturation. The results revealed that although a slope of 1:12, as recommended by ADAAG, is suitable for a wide range of users with mobility aids, it poses a barrier for some users with manual wheelchairs, especially the elderly. However, the study still recommended retaining the 1:12 slope until a substantial approach is proposed. Another study explored navigating ramps in different snow and ice-grit conditions in Ottawa, Canada [19]. The study involved 11 participants with various mobility impairments who normally self-propelled their wheelchairs during winter, recruited through a rehabilitation centre. The participants navigated portable ramps with three different slopes (1:10, 1:12, and 1:16), tested in indoor conditions simulating two winter scenarios. Navigation strategies were recorded using digital video, and participants’ viewpoints were evaluated through a questionnaire survey. The average speed during ramp ascent and descent was also measured. The slope of 1:16 was found to be preferred in snow and ice-grit conditions. Study limitations included inconsistent snow conditions and a nonhomogeneous sample population. Although the study highlighted the need for research on winter maintenance, the ratings were primarily based on participants’ perceptions.

The compliance of curb ramps in an urban area with the ADAAG was investigated in a study in 2009 [20]. An assessment tool based on 8 accessibility criteria was used to evaluate 79 intersections in Halifax, Nova Scotia, Canada. Scores 1 and 0 were used if the criterion was met or not, respectively. A descriptive analysis following the qualitative measurements was conducted to identify the main barriers. The study did not involve any participants. Most intersections failed to meet all 8 criteria set by the accessibility standards, with only 3% meeting the criteria. The flow of gutters was noted as a barrier due to water or ice buildups. Moreover, another study aimed to explore the effect of surface characteristics on the mobility of users with manual wheelchairs traversing a surface [21]. The participants were users with wheelchairs enrolled in an engineering research laboratory registry. The two-phased study utilized paper-based questionnaire surveys in the first phase and online-based surveys in the second phase. In the first phase, participants were asked to rate the difficulty of 66 pictures representing different cross slopes, from 1 to 5. In the second phase, participants were asked to answer four questions relevant to their responses to the same scenarios in various weather conditions and surface integrity. Among several barriers presented to the participants, severe cross slopes were found to be the most challenging, particularly in harsh weather conditions. The pictures and design of the first phase survey confused some participants. The study excluded individuals with progressive diseases who use manual wheelchairs.

Several research studies aimed to address floor surface characteristics, particularly parameters that are not clearly defined in standards, such as “roughness” or “evenness”. The unevenness of sidewalks was evaluated in Sapporo, Japan, by measuring the resistance of wheelchairs with a developed torque-measuring device [22]. After testing the device on various in-service sidewalks with different gradients, a 5 m long test track was constructed to investigate the relationship between sidewalk unevenness and the users’ discomfort level. To ensure the randomness of the sample, a questionnaire survey on the discomfort of wheelchair travel was distributed during an annual festival attended by many students and residents, where 576 users with different manual wheelchair efficiencies participated in this experiment. The participants were later asked to rate their discomfort level. The reported discomfort rate increased linearly when the gradient exceeded 2%. However, the results apply only to 5 m long sidewalk segments.

Another study developed a measurable standard for the surface roughness of pathways used by individuals with wheelchairs [23]. Sixty-one participants who use manual and powered wheelchairs completed a baseline questionnaire on their experiences with commonly navigated pathways. Afterward, they navigated a 16-ft indoor wooden test platform with various surface roughness. A subset of the participants also traversed six outdoor surfaces using their wheelchairs. Triaxial accelerometers recorded the vibrations in the wheelchairs. Following the walkthroughs, participants rated the adequacy of each surface using a rating form. The vibrations were converted to root mean squared accelerations (RMS), which were then compared with surface roughness. The survey revealed that almost half of the participants were unsatisfied with their commonly travelled pathways. The surface roughness was found to be directly proportional to the RMS. Some surfaces were found to cause harmful vibrations for the users, as their RMS accelerations were above 1.6 m/s², which is harmful over a 1 h period as per ISO 2631-1. Damaged and warped pathways were found to be challenging, and surfaces with wide and frequent cracks were viewed to produce whole-body vibrations (WBVs) [24]. This indoor experiment was limited to wooden surfaces only, and participants were found to experience visual bias, which led to rating the surfaces lower than the data indicated. Additionally, some participants withdrew from the study before all surfaces were completed. A subsequent study tested the WBV exposure and pathway roughness index (PRI) as practical thresholds [25]. The results proposed a PRI of 50 mm/m for a surface segment of 100 m or more and 100 mm/m for a surface segment less than 3 m to protect users with wheelchairs against discomfort and possible health risks due to vibration exposure. It should be noted that since the vibration sensors were located under the seat of the wheelchair, they may have detected vibrations that did not exactly match what the users felt due to the seat cushion.

Wayfinding constitutes another accessibility feature that is difficult to evaluate and has consequently been a focus of accessibility research. A new approach was proposed to evaluate the effectiveness of navigation/wayfinding on sidewalks [26]. The methodology involved developing a simulation model of sidewalk segments, utilizing the sidewalk network database of the University of Pittsburgh’s main campus that adheres to accessibility parameters based on ADA recommendations. Different wayfinding scenarios were simulated for users who use wheelchairs by assigning varying weights for sidewalk parameters, including sidewalk slope, width, length, surface type and condition. The simulation results were visualized using heat maps and classified into comfortable, semi-comfortable, uncomfortable, and inaccessible areas. The proposed model has not been tested to reflect human behaviours. Another study proposed an extension for a geospatial data model, integrating accessibility data for people with mobility impairments utilizing wheelchairs [27]. The study attributed the gaps in current wayfinding systems to the lack of alignment with available accessibility standards, the lack of free and open accessibility data that can assist in the simulation models, diverse needs of people with disabilities which might result in solutions that are not suitable for everyone, and lack of testing in real-world applications considering the feedback from people with lived experience. The study was limited to accessibility data for users with wheelchairs.

Evacuation provisions are another feature that has evolved as it is not only an accessibility requirement but also a safety concern, particularly for people with limited mobility who need assistance. Thus, it has always been of interest to researchers, with earlier research focusing on highlighting the shortcomings of the accessibility standards in addressing emergency provisions. A study in 1994 reviewed the standards and theories of buildings’ egress in the UK, particularly the 1980 “BS 5588: Part 8 Code of Practice for Means of Escape for Disabled People”, to identify deficiencies and potential risks [28]. The study highlighted the absence of guidelines related to lateral evacuation, escape elevators, and refuge areas. It emphasized the need to consider the mixed abilities and psychological factors of individuals during evacuations to provide safety options beyond code compliance. Christensen et al. reviewed the accessible egress requirements outlined in the “Americans with Disabilities Act (ADA) Accessibility Guidelines” in 2007 [29]. The study revealed that these requirements were more oriented toward planned evacuation systems, i.e., protocols, procedures, and organized responses, rather than the built environment, which may influence the safety of individuals due to receiving mixed instructions and directions in some environments. Recent studies in this field incorporated the perceptions of people with disabilities.

A study investigated the perspectives of occupants with mobility impairments on various evacuation methods during fire emergencies [30]. The study involved 51 participants with varying mobility aids, working in buildings across five U.S. metropolitan areas. In-depth semi-structured interviews were conducted to discuss both typical evacuation methods, such as emergency stair travel devices and areas of refuge, and modern occupant evacuation elevators. Emergency stair travel devices allowed for immediate evacuation are reported to induce anxiety during transfer to the device. While some participants appreciated the protection offered by areas of refuge, others were concerned about being left behind. Existing elevators were found to be overcrowded and inefficient. Occupant evacuation elevators offered safer alternatives by allowing users to stay on their devices and evacuate based on the level of risk. However, there were concerns about prioritizing individuals who are ambulatory over individuals with mobility impairments. The study emphasized the necessity of including those with mobility impairments in planning and executing fire evacuations.

3.2. Overall Accessibility

Most recent research primarily focuses on evaluating the overall accessibility of buildings and public facilities, rather than examining the feasibility of accessibility provisions for specific features, as previously mentioned. These studies gathered insights from individuals with lived experience or professionals without lived experience using existing/modified checklists from various local and international accessibility standards.

Several studies assessed the accessibility of built environments from the viewpoint of people with disabilities. A study in Romania employed four online personal blogs and three discussion forums to explore the insights of people with disabilities towards their built environments [31]. Online search engines were used to identify blogs and forums focused on physical disabilities. The inclusion criteria included free-accessed online blogs and forums written in Romanian. After filtering the comments to the ones written by owners or forum members who have lived experiences with mobility disabilities, 364 comments were included in the final data analysis. Major barriers included a lack of ramps and elevators, or poorly designed ramps with steep slopes and inadequate handrails. The study attributed accessibility barriers, based on the comments, to the exclusion of feedback from people with disabilities in the policy-making processes and the lack of awareness of some individuals who failed to uphold the rights of people with disabilities. For instance, some bus drivers do not lower the ramp for those who need it.

In a different study, the impact of accessibility on the attractiveness of public spaces for people with disabilities was highlighted in Algiers, Algeria [32]. The research approach involved observational walkthroughs and semi-structured interviews with people with physical disabilities, selected through associations, social networks, and mutual acquaintances. Prior to the observational walkthroughs, 60 participants were interviewed, of which 30 were carefully analyzed to gather their insights on their urban built environments. The walkthroughs engaged 6 participants, each using a different assistive device. The participants rated their comfort level on a scale from 1 to 5. The study shed light on the negative impact of inaccessible urban environments on the travel choices and daily activities of people with disabilities, as per 40% of the participants. The participants identified several physical barriers, such as a lack of curb ramps, the absence of accessible parking spaces, the presence of steps and stairs, narrow and steep pathways, uneven surfaces, and inaccessible washrooms. Nevertheless, due to the limited and self-reported participants, the findings may not encompass the diverse experiences of all individuals with physical disabilities. Additionally, due to the qualitative nature of the study, the insights cannot be generalized.

Another study in Islamabad, Pakistan, assessed the accessibility of commercial areas for people with physical disabilities [33]. The study involved 277 participants with mobility impairments who use wheelchairs. The sample size was calculated for an estimated population of 20,000 using a 95% confidence interval. The inclusion criteria involved people with physical disabilities who use wheelchairs and excluded those who use wheelchairs temporarily and people with mental disabilities who use wheelchairs. The study utilized self-structured accessibility questionnaires covering parking spaces, sidewalks and walkways, entrances, hallways, main reception, and washroom facilities. The most frequent barriers were the lack of designated accessible parking (53%), the absence of handrails in walkways (43%), and heavy entrances (42%). The study was limited to a specific geographic area and relied on self-reported data and participants’ experiences.

Other research studies engaged professionals, students, researchers, or accessibility experts without lived experiences to evaluate the overall accessibility of a building or facility. Some studies evaluated the accessibility of recreation facilities and parks by adopting the Accessibility Instruments Measuring Fitness and Recreation Environments (AIMFREE) scoring system. This system, developed by a team at the University of Illinois at Chicago, US, aims to identify barriers across different attributes, including the built environment, equipment, policies, and staff training and behaviour. To align with the scope of this study, only barriers in built environments are mentioned. The accessibility of 44 fitness and recreation facilities in Ontario, Canada, was evaluated utilizing a modified version of AIMFREE [34]. The “universal” accessibility of spaces, including entrances, access routes, washroom facilities, doorways, elevators, and parking spaces, was assessed by a trained researcher and principal investigator. All the facilities received a low overall universal accessibility rating, particularly the washrooms. The study highlighted the need for specific accessibility guidelines for recreational and fitness facilities, recommending the adoption of the ADAAGs. Another study utilized AIMFREE to evaluate the accessibility of 227 fitness facilities across 10 states in the US by trained evaluators [35]. The evaluators were physical or occupational therapy students and staff. Overall, only 35% of the fitness facilities were found to be accessible. Most barriers were identified at entrances, access routes, signage, and washrooms. It is worth mentioning that the results did not include the facilities whose owners or managers had concerns about participating in the study. Moreover, the accessibility of 21 public parks and playgrounds was evaluated in New Zealand [36]. Out of 92 parks, 18 were selected by stratified random sampling, and 3 were selected by purposive sampling based on the city councils’ recommendations. A customized evaluation tool was developed by adapting aspects relevant to parks and playgrounds from the professional version of AIMFREE, modified to align with the recommendations of national and international standards for accessibility. The development of the tool involved consulting accessibility advocates and city council officials, in addition to a pilot assessment before the actual site visits. The key areas involved parking spaces, access routes, lighting, rest areas, washroom facilities, and water fountains. None of the parks met the national or international guidelines and standards. Some common barriers included inaccessible parking spaces, lack of signage and tactile surface indicators, inadequate lighting, and inaccessible routes, washrooms, and water fountains. The study highlighted the need for further psychometric testing of the evaluation tool.

In another study, an initiative to enhance campus spaces based on Universal Design (UD) principles was introduced by the Faculty of Architecture students at the Silesian University of Technology, Poland [37]. The students were asked to assess all facilities, including the parking area, accessible routes, entrances, vertical and horizontal circulation, washroom facilities, classrooms, meeting rooms, and emergency evacuations. The students reported several barriers, such as the lack of accessible parking spaces, inadequate colour contrast, high curbs and thresholds, absence of elevators, poor wayfinding cues, inaccessible workspaces, narrow doors, and poor evacuation systems. Another study explored accessibility barriers in recreation sites in British Columbia, Canada [38]. The study employed a community-based research approach, where academic researchers and accessibility experts conducted site visits to collect data and measurements across 124 tourism and recreation sites. None of the sites was recognized as barrier-free, with 95% featuring at least one barrier. The most frequent barriers were identified at parking spaces, washroom facilities, and seating areas. The sites were selected in consultation with partners, which is a non-random approach that lacks generalizability. Also, data was collected only during summer and fall, omitting the perception of accessibility during spring and winter. The study emphasized the need for evidence-based research that considers the voices of people with disabilities.

Few research studies recognized the significance of acknowledging various needs and abilities. In such studies, the perspectives of people with lived experiences are integrated alongside the insights of accessibility professionals without lived experiences to highlight the differences in needs. A study in Ontario, Canada, highlighted how different groups, including students, principals, and special education resource teachers (SERTs), perceive accessibility in schools [39]. Observational walkthroughs were carried out independently by each group to identify architectural barriers in elementary and secondary schools. The study involved 29 schools with students with physical disabilities who use various assistive aids and 22 schools with students without physical disabilities, all drawn from a school board in Ontario. An objective checklist was used to identify the barriers, including entrances, access routes, ramps, doors, washrooms, signage, water fountains, elevators, classrooms, stairs, libraries, and recreational facilities. The study revealed that students identified more barriers than both the principals and SERTs, particularly in identifying barriers in doors and elevators. Interestingly, the students identified some barriers missed by an accessibility auditor. The study did not compare the barriers identified by students with and without physical disabilities. Overall, students mainly reported barriers at the entrance, access routes, doors, signage, classrooms, libraries, and recreational facilities. The principals reported barriers at the entrance, signage, stairs, and water fountains. The SERTs reported barriers at the ramps, washrooms, and elevators. The study highlighted the need for a consistent methodology for assessing accessibility barriers that acknowledges unique perspectives. The research method was found to lack control due to the independent assessments conducted by the students, the selection criteria set by the school principal, and the presence of known confounding factors that might influence the participants’ perceptions.

In a different study, the perspectives of tourists with varying disabilities towards national parks were explored in several countries [40]. A mixed-method approach was employed, involving the development of a questionnaire that was adopted from the literature and modified to the needs of tourists with physical, visual, and hearing disabilities. Participants were recruited through contacting international organizations for disabilities and online forums. Additionally, panel discussions were conducted with representatives of accessibility organizations and parents of children with disabilities, focusing on their expectations when visiting parks. The responses of 121, 31, and 20 participants with physical, visual, and hearing disabilities were collected, respectively. The study addressed various accessibility features and elements, such as reception areas, trails, walkways, and washrooms. Steps and stairs were identified as significant barriers for all disabilities, with people with mobility impairments mostly concerned about parking and entrances.

4. Status of Research Pertaining to Sensory/Vision Disabilities

The WHO World Report on Vision in 2019 reported that at least 2.2 billion people live with visual impairments around the world [41]. Consequently, it is imperative to create inclusive and accessible built environments that enable those individuals to navigate independently and safely. Research on people with visual disabilities either addressed accessibility features such as emergency provisions, navigating accessible routes, information kiosks, or evaluated the overall accessibility of buildings and facilities, like research on people with physical disabilities.

4.1. Specific Accessibility Features

Few studies focused on emergency provisions, mostly addressing social and behavioural factors that might influence the experience of people with visual impairments during emergencies. Accessibility standards, such as ADAAG, require the inclusion of visual and audible emergency alarms to warn people during emergencies. A previously mentioned review study suggested that these alarms are part of the preventive system designed to guide individual behaviour during evacuations and do not necessarily contribute to an accessible built environment [29]. The study highlighted that such preventive systems pose significant challenges for people with visual impairments, who prioritize seeking safety over complying with such systems. Thus, it emphasized the need for further research on accommodating the behavioural factors of individuals with visual impairments during evacuations.

Wayfinding and navigation, whether indoors or outdoors, pose major barriers for people with visual impairments. Thus, it is one of the most evolving and progressing topics in research relevant to people with disabilities. A study observed wayfinding for people with visual impairments during walkthroughs of two shared-use and two conventional spaces in Groningen, the Netherlands [42]. The study involved 25 participants who are blind or with low vision, with/without assistive aids. The participants were recruited through telephone interviews. Inclusion criteria included those without any other impairment but visual, capable of independent mobility, and unfamiliar with the sites. Another previously mentioned study developed a simulation model to assist pedestrians in navigating sidewalks at the University of Pittsburgh [26]. Different scenarios for those who are blind or with visual impairment were proposed. The weights assigned to sidewalk parameters were adjusted, particularly those for slope and crosswalk, compared to users with wheelchairs. The sidewalk segments were then categorized into accessible and inaccessible zones, visualized by heat maps. However, the model was not tested.

Another study investigated the barriers in indoor public spaces with limited environmental cues [43]. The study involved 15 sighted professionals and 30 individuals with visual impairments. The participants completed a survey questionnaire with 18 open-ended and closed-ended questions, followed by semi-structured interviews. The questions focused on assistive technologies, wayfinding, and orientation strategies. Thirty-four percent of the participants identified their location by estimating the distance from a sighted guide, 30% relied on landmarks, and 24% utilized environmental cues such as light, noise, and odour. The use of smartphones was found to be limited. Additionally, up to 70% of the participants reported avoiding unfamiliar spaces due to the need for a sighted guide. Many other barriers were reported, such as the noise in crowded areas leading to disorientation, quiet spaces causing panic due to the lack of feedback, non-cane-detectable headroom and protruding objects, slippery floors, and excessively bright light causing temporary blindness. In a different study, various solutions and software applications pertaining to indoor and outdoor wayfinding and navigation for people with disabilities were explored [44]. The study reviewed various technologies designed to aid people with visual disabilities in navigating indoor and outdoor environments, such as iCampus and NavCog. It highlighted the lack of involvement of people with disabilities during the design and feedback stages.

Designing safe pedestrian crossings for people with visual impairments is another feature that is crucial and needs comprehensive research. A study in 2010 outlined the barriers encountered by people with varying sight loss while navigating urban environments and proposed solutions to improve their safety and accessibility [45]. The study involved interviews with professionals and observed journeys of 8 participants with varying degrees of sight loss and assistive aids, such as residual sight, long canes, and guide dogs. These participants shared their navigation experiences during regular unaccompanied trips in and around London. Based on the mental maps they created, participants suggested including tactile paving, signal-controlled crossings, audible signals, and consistent street layouts to improve the accessibility of urban streets. However, the small sample did not necessarily reflect the experience of all individuals with low vision. Another study proposed installing newly designed orientation blocks at crosswalks to help people with visual impairments identify their pathways while crossing [46]. The study aimed to determine the optimal location of orientation blocks relative to tactile walking surface indicators. Twenty-one participants, who were completely blind, walked a 10 m experimental path simulating a road crossing. Their walking routes were video recorded, and thorough interviews were conducted to gather their feedback. The orientation blocks were placed at various locations. The results indicated that separating orientation blocks from tactile surfaces by 8 cm can reduce mental stress and limit the lateral deviation during crossing.

Information kiosks are another feature of interest for researchers recently, particularly for people with sensory disabilities. In the study mentioned earlier about information kiosks in Korea, the design requirements of accessible kiosks for people with visual disabilities were investigated [47]. Through the focus group interviews, 11 people with visual impairments emphasized the need for voice support and high contrast between the content and the background of the kiosks.

4.2. Overall Accessibility

Several studies explored open outdoor spaces and facilities, highlighting the need for well-designed, safe, and accessible environments for people with visual impairments. A study in Hong Kong investigated the accessibility of parks for people with visual impairments through a case study conducted between 2009 and 2011 [48]. The participants were recruited through non-governmental organizations, including 12 individuals with visual impairments working with these organizations. The study involved site visits to six parks, followed by workshops. The participants were asked to assess the overall accessibility of the parks and the indoor facilities. Additionally, interviews were conducted with government representatives and park designers. Participants reported avoiding unfamiliar spaces due to challenges identifying and navigating them independently. They also noted that information about the parks often lacked supportive features such as Braille and audible cues, in addition to limited or poorly designed tactile paving. The government and parks representatives suggested that tactile maps at the entrances were sufficient, which did not reflect the needs of people with lived experiences. The findings were based on the perception of the small sample.

Another study aimed to explore the outdoor accessibility experiences and the role of mobile devices and GPS technology in fostering accessibility for people with visual impairments [49]. The study utilized an online questionnaire survey, which was distributed to various associations and communities of people with visual disabilities, as well as online forums and mailing lists. The survey was completed by 97 participants who are blind or with low vision from 13 countries, primarily developing nations. The most frequently reported barriers were the lack of audio information (82%), the absence of audio output in traffic lights (81%), and difficulty in locating facility entrances (65%). Also, 36% of participants who are blind and 21% who have low vision reported difficulties navigating spaces independently. While most participants found mobile devices and GPS navigation tools useful during their trip, significant challenges were reported. Particularly, 70% reported a lack of environmental accessibility data, 58% noted the map data were outdated, and 55% experienced inaccuracies in the GPS location. These results were biassed due to self-reported participants and the infrastructure of the developing countries.

In a different study, seven individuals who are completely blind were interviewed to share their experiences navigating outdoor environments [50]. The study aimed to address the research gap due to the lack of insights from people with lived experiences. The interviews were conducted online or via phone, focusing on three themes being “independence”, “knowledge of the environment”, and “sensory experiences”. The findings highlighted a significant gap between human–computer interaction (HCI) research and current technology in providing solutions for people with visual impairments. Additionally, participants emphasized the need for independent navigation experiences without sighted guides. The lack of accessible landmarks and wayfinding information obliged the participants to rely on navigation applications that lacked accessibility features. The results were subjective to participants’ perspectives and needs. In the previously mentioned study on park accessibility for tourists with disabilities, the responses of 31 participants with visual impairments revealed the significance of information accessibility [40]. Participants highlighted the lack of essential information in Braille and non-text formats. They also stressed the need for accessible websites incorporating audio descriptions. Despite the comprehensive evaluation criteria, the questionnaire focused mainly on mobility impairments.

Another study on the accessibility of public transit collected insights from 13 individuals with visual impairments who are blind or have significant sight loss during a focus group discussion [51]. Participants reported the lack of accessible pedestrian signal (APS) devices at crosswalks and deteriorated sidewalks leading to falls as major barriers. Furthermore, they highlighted that navigating crowded roads to reach bus stops or carry out daily activities, particularly in the absence of APS devices, compromises their safety.

5. Status of Research Pertaining to Sensory/Hearing Disabilities

According to the WHO World Report on Hearing in 2021, over 1.5 billion people worldwide experience some degree of hearing loss [52]. These individuals often encounter numerous accessibility barriers in built environments due to the lack of auditory and communication cues [53,54,55]. Although accessibility standards seem to be progressing in the right direction in addressing the needs of people with hearing impairments, many of these improvements are merely recommendations or not clearly defined. This challenge is even exacerbated by limited research in this field.

5.1. Specific Accessibility Features

Research addressing specific accessibility features for people with hearing disabilities was found to be scarce. In the previously mentioned study on information kiosks in Korea, 10 individuals with hearing impairments shared their experiences when using the kiosks [47]. The major issues included the lack of alternative feedback options aside from voice, such as visual cues like light, blinking, captions, or images. Users also emphasized the need for assistive staff who can communicate in sign language.

5.2. Overall Accessibility

Most research on accessibility for people with hearing disabilities focused on the overall accessibility of built environments, mainly discussing spatial proximity requirements to facilitate communication. Pérez Liebergesell et al. explored vision-centred architecture through the lens of a deaf architect, George Balsley [56]. The researchers conducted interviews and guided tours with Balsley to gather insights on his design of the Sorenson Language and Communication Center (SLCC) in Washington, DC. His design demonstrated the integration of visual and spatial features that facilitate sign communication. Balsley emphasized several key features when designing spaces for those with hearing impairments. These include incorporating automatic glass doors, wide spaces filled with natural light to help mediate sign language from a distance, gentle and wide ramps, and rounded wall edges. He also highlighted the importance of clearly located features, like elevators, and suggested adding windows to enhance the visibility of inside-outside views. Furthermore, Balsley proposed incorporating automatic closing devices for fire-resistant doors that are only activated during emergencies. Additionally, he recommended offering social and gathering spaces with various seating arrangements with armrests, ensuring colour contrast between different structural elements, and reducing glare from sunlight and artificial lighting using recessed light fixtures. Despite the significant insights, the study was based on a single case study, interviewing one person.

Another study investigated how spatial configurations affect communication among people with hearing impairments in public places [57]. The study involved interviewing individuals with hearing impairments in Kopi Tuli, a cafe designed for the community of those with hearing impairments, to gather their insights. The café was found to offer various proxemic zones along with thoughtful seating and furniture arrangements. Furthermore, semi-reflective surfaces and transparent materials were used in the café, creating a comfortable atmosphere for individuals with hearing impairments while ensuring accessibility.

In another study, five academics with hearing impairments were interviewed to gather their insights on navigating their workplaces at Higher Education Institutes (HEIs) [58]. The study involved walking interviews to examine various factors influencing sign language communication. Participants noted several barriers, including narrow hallways and pathways, which made it difficult for two individuals to sign comfortably side by side. In addition, physical obstacles were observed along the hallways and pathways. Interestingly, besides accessibility concerns, participants reported the need for safety adaptations, such as fire alarms with flashing lights, flashing doorbells, or fire alarms connected to personal devices. They also shared their adaptation strategies to enhance accessibility in their workspaces, like rearranging desks to create more space for communication or placing mirrors to monitor approaching individuals.

In a previously mentioned study, 20 tourists with hearing impairments shared their experiences while navigating national parks [40]. The study emphasized the need for staff trained to communicate in sign language. It also acknowledged the distinct needs of people with disabilities. For instance, people with hearing impairments were primarily concerned about the accessibility of reception areas, whereas those with mobility impairments prioritized parking and entrances. Although a comprehensive questionnaire was used in the study, the focus was on those with mobility impairments.

6. Status of Research Pertaining to Cognitive/Intellectual Disabilities

Due to the heterogeneity and variations in cognitive/intellectual disabilities, it is quite challenging for accessibility standards to meet all the unique needs of individuals with these disabilities and establish standardized requirements. The lack of accessibility provisions is further intensified by limited research in this field. There are only a few tentative efforts to explore the accessibility requirements for people with cognitive/intellectual disabilities.

6.1. Specific Accessibility Features

The lack of research on people with cognitive/intellectual disabilities is not surprising. Only a few studies focused on assessing specific features, in particular emergency provisions. Shields et al. investigated the responses of 28 individuals with learning disabilities during unannounced evacuation at two residential care facilities in Northern Ireland [59]. The unannounced evacuations were recorded on video to capture the occupants’ reactions. The care assistants were instructed to intervene only when necessary. A range of responses were observed, including refusal to evacuate, slow evacuation, and lack of mutual assistance. These responses were influenced by social factors such as fear and cognitive and mobility abilities affecting information processing. The study emphasized correlating learning difficulties with evacuation behaviour while designing evacuation protocols. Another study highlighted the lack of research on evacuation procedures for occupants with intellectual impairments, with most research focused on specific case studies [60]. The study emphasized the need for periodically repeated and consistent long-term training on evacuations for people with intellectual disabilities. Moreover, Zakour highlighted the need for social support during evacuations, which is hard to incorporate into accessibility standards [61]. The study involved interviews and survey questionnaires, reaching 710 individuals with disabilities across the US through random digit dialling to households and mailings to healthcare centres. The study did not specify participants’ disabilities.

Bochi conducted a scoping review to assess evacuation strategies for people with functional limitations [62]. The study underscored a significant research gap in this area, with only 3 articles focused on functional disabilities compared to 48 targeting mobility impairments. It also revealed the necessity for more customized evacuation solutions, particularly on notification and wayfinding for various disabilities like autism, anxiety, or other cognitive impairments. Given the diverse needs of this population, the study highlighted the need for further research that considers distinct information processing, problem-solving abilities, and attention in stressful situations.

Navigation presents another real challenge for people with cognitive/intellectual disabilities, particularly in environments that lack adequate environmental cues and supportive features. Castell highlighted the limited research on equitable access requirements for people with intellectual disabilities relative to those with physical and sensory disabilities in the Building Code of Australia (BCA) [63]. The study involved an extensive review of case studies and research on access requirements for individuals with intellectual disabilities. The findings revealed that wayfinding is particularly challenging for those individuals due to difficulties in obtaining and processing information. The study also emphasized the need to promote building designs that incorporate features such as consistent layouts, clear signage, maps, landmarks, appropriate lighting, and human assistance.

6.2. Overall Accessibility

Research relevant to the accessibility of built environments for people with cognitive/intellectual disabilities is typically within silos such as medical, social, and engineering. This study focuses solely on the “engineering” aspects. Unsurprisingly, limited initiatives addressed overall accessibility in built environments, with most research aimed at identifying potential encountered barriers.

In a study aimed to evaluate the accessibility of a town centre in Kristianstad, Sweden, the perspectives of teenagers with varying functional limitations using various mobility aids were gathered [64]. Despite the wide range of functional limitations represented in the study, the encountered barriers were not classified according to these limitations. Another study reviewed the literature on the accessibility of indoor and outdoor environments for people with dementia [65]. Most research was found to be influenced by personal stories and needs shared by carers, not individuals with lived experiences. The study suggested conducting research informally over a period, with people with dementia, their carers, and researchers working together to identify difficulties and explore solutions. The study also advocated for shifting the focus from the “medical” model to the “social” model during the planning and design processes, suggesting that focusing on the medical model may result in neglecting necessary adaptations for built environments. The study indicated that accessible environments could enhance the functional capacities of people with dementia. The improvements in spatial orientation result in reduced social stress.

In a different study, barriers encountered by families living with children with physical and cognitive impairments in their residential environments in Torbay, UK, were investigated [66]. The study included questionnaire surveys and focus groups with parents of children recruited via a school for special needs. Additionally, housing builders conducted surveys, and eight policy professionals were interviewed to provide their insights on relevant policies. The families reported several barriers resulting from inadequate housing sizing and storage space, poor access, and inadequate soundproofing. The parents were also asked to evaluate their level of satisfaction with their current residential accommodation. The level of satisfaction varied based on the diagnosis of the child, where families of children with trisomy and motor sensory neuropathy were the least satisfied, followed by autism, then cerebral palsy and attention deficit hyperactivity disorder (ADHD).

A recent study investigated the accessibility of 15 museums in London, UK, compared to another 15 museums in Thessaloniki, Greece [67]. The spatial and information accessibility were examined for people with physical and intellectual disabilities. The methodology involved semi-structured interviews with museum representatives and site observations using an accessibility checklist developed based on guidelines and scientific papers initiated by the researcher. The study suggested adopting measures like simple language for information on exhibits and graphics for guidance. Accessibility standards do not provide much guidance on such instructions. The study indicated that most accessibility features targeted individuals with physical impairments, with less attention given to sensory and cognitive barriers.

7. Analysis and Discussion

A close examination of the sample of refereed journal articles and conference papers on accessibility within built environments revealed a predominant emphasis on physical disabilities, constituting nearly half of the reviewed sample, as demonstrated in Figure 2. In contrast, cognitive/intellectual and hearing disabilities are less represented, comprising only 13% and 7% of the sample, respectively. This trend is also evident in accessibility standards. For illustration, 20% of Canada’s accessibility standard, CSA/ASC B651:23, provisions address hearing impairments and 7% cognitive/intellectual barriers [9]. The alignment of the data indicates that accessibility standards are limited by prevailing research at the time of their publication.

Beyond barriers and features, research on accessibility was found to be profoundly influenced by research methods and participant inclusion criteria. As illustrated in Figure 3, research is progressing in the right direction, as nearly 45% of participants’ criteria utilized in research studies incorporated feedback and insights from people with lived experiences. However, even within the same group of disabilities, there is room for personal views and preferences, as what works for some individuals does not necessarily reflect others. Among the studies involving participants with lived experiences, only a few accounted for a spectrum of impairments, often failing to differentiate between or report their unique needs [30,39,40,47,51,64,68,69]. Therefore, the inclusion criteria and corresponding analysis of research results should account for varying disabilities, severities, and assistive aids. Additionally, approximately 17% involved individuals with non-lived experiences, and nearly 22% did not involve human participants. Insights of people who did not experience disabilities and untested simulation models by people with lived experiences may fail to address the true needs of people with disabilities. Consequently, these approaches and corresponding findings can taint the information pool and create unchecked biases that can delay and misguide the development of accessibility standards.

In terms of research methods, Figure 4 shows that nearly 50% of the methods utilized in research studies were focus groups, interviews, and survey questionnaires. The participants were often self-selected, which allows room for biassed interpretations and personal perceptions. Research should involve a statistically representative random sample of participants. Additionally, only 10% and 6% utilized experimental setups and models, respectively. This finding indicates that there is a need for more data-driven research to guide the development of accessibility standards.

Figure 5 illustrates some of the features reported in research studies on overall accessibility in built environments. The data, which is a representative sample, indicates that the most frequently mentioned features are washroom facilities and floor surfaces, followed by doors and doorways. These features represent “physical barriers” that mostly impact the accessibility of people with physical disabilities. The accessibility standards extensively addressed these barriers in comparison to the needs of people with sensory and cognitive/intellectual disabilities, such as luminance, assistive listening systems, or emergency provisions. For illustration, CSA/ASC B651:23 clause 6.2, which presents the requirements for Washroom facilities such as floor area, accessories, and grab bars, has been part of the standard since its first edition. In contrast, clause 4.2, which deals with Luminance (colour) contrast, was introduced in the latest edition of the CSA/ASC B651:23 to assist facilitating wayfinding.

7.1. Physical Disabilities and the Built Environment

Delving into research on accessibility in built environments for people with physical disabilities revealed that approximately one-third of the studies aimed at evaluating the overall accessibility of the built environments rather than assessing specific accessibility requirements, as shown in Figure 6. Research that evaluates the compliance of built environments with existing accessibility standards does not necessarily contribute to the evolution of accessibility standards. This may sometimes foster a “checkbox approach” by trying to meet the minimum requirements rather than highlighting true barriers that adversely impact the accessibility experiences of people with disabilities.

The predominant focus of the research was on exterior circulation and amenities, which constituted approximately 43% of the reviewed papers. This area of focus encompassed various features such as accessible routes, ramps and curb ramps, transit stops, information kiosks, etc. This result is not surprising, given the challenges people with physical disabilities often encounter when navigating outdoor spaces due to inaccessible routes, poor wayfinding, poor weather maintenance, and physical obstructions. Moreover, almost half of the studies pertaining to circulation focused on accessible routes and ramps, with several studies emphasizing the need for guidelines addressing winter maintenance [70], surface characteristics including firmness, roughness and evenness [22,23,25], and wayfinding [26,27]. The CSA/ASC B651:23 standard provides comprehensive requirements for accessible routes, including width, slope, and drainage. However, there remain areas to be clearly defined and addressed, such as snow maintenance and surface characteristics like “slip-resistance”, “evenness”, etc. The research should focus on adopting/developing methods or experimental approaches to assist the standard in developing adequate prescriptions.

A few studies focused on area allowances, which accounted for almost 5% of the reviewed sample [15,16]. The lack of research could be attributed, in part, to the thoroughness and evolution of accessibility standards relevant to floor areas. For instance, in the first edition of CSA B651 and up to 2010, the minimum floor maneuvering area required for a wheelchair at a stationary position was 750 × 1200 mm and 1500 × 1500 mm for U-turns [10,11,12]. These dimensions have been modified in subsequent editions based on anthropometric data until they became 820 × 1390 mm at a stationary position and 2100 × 2100 mm for U-turns in the recent edition [9,13,14]. According to CSA/ASC B651:23, these dimensions accommodate the 95th percentile of all wheeled mobility devices and account for those using crutches, walkers, white canes, or service animals. Accessibility Research played an essential role during this process, particularly in including various assistive mobility devices with different dimensions [15,16]. Studies focusing on signage were found to be scarce, which requires more research focusing on indoor and outdoor solutions that cater to diverse needs, assistive aids, and technologies.

In terms of interior circulation, accessibility standards cover several features. For instance, the guidelines outlined in CSA/ASC B651:23 cover accessible routes, doors and doorways, stairs, ramps, elevating devices, and emergency provisions. This may justify the lack of recent research. To our knowledge, no recent studies have addressed such features. Beyond the physical barriers, research on emergency provisions, representing about 8%, focused on investigating social and psychological factors influencing the responses of individuals during evacuations [28,29,30]. This type of research, although essential, poses a challenge for accessibility standards as such parameters are difficult to measure and implement and thus do not directly assist in updating guidelines for evacuation plans and areas of refuge. CAN/CSA-B651-M90 provided few requirements, primarily focusing on areas of refuge, compared to the recent CSA/ASC B651:23, which offers detailed guidelines addressing visible alarms, areas of refuge, evacuation plans, and access to secure areas.

Research relevant to interior facilities has primarily focused on washroom facilities, which represented 8% of the reviewed sample. For instance, to our knowledge, no recent studies addressed features such as adult change tables, change benches, seating, or locker rooms, although they are part of the accessibility standards. Additionally, studies related to washroom facilities are oriented mainly toward compliance with accessibility standards rather than identifying true barriers beyond the standard’s minimum requirements.

In terms of vehicular access, the CSA/ASC B651:23 covers pedestrian routes, passenger pick-up areas, designated accessible parking, and ticketing dispensers or payment machines. The thoroughness of these guidelines likely justifies the limited research relevant to this area, which accounted for 3% of the reviewed studies, mainly focusing on designated accessible parking.

7.2. Sensory/Vision Disabilities and the Built Environment

Accessibility standards are making progress in addressing the needs of people with visual impairments. For example, CSA/ASC B651:23 made a notable advancement with nearly 61% of major features offering guidelines that directly or indirectly influence those with visual impairments. These include features such as audible and tactile cues, detectable warning surfaces, braille signage, illumination, and luminance contrast. Despite these valuable efforts, the limited research in this field contributed to the slow evolution of accessibility standards for people with visual impairments. Therefore, more research in this field is essential to back up the ongoing evolution of accessibility standards.

Furthermore, reviewing the literature revealed the need for more comprehensive approaches, particularly to assess the accessibility of routes, stairs, ramps, and emergency evacuations. Such approaches need to be validated by those with lived experiences to help refine the existing guidelines and/or introduce new ones as needed. Additionally, there remain aspects that require further investigation, such as illumination and indoor wayfinding, while recognizing that what might work for people with one type of sensory disability may not necessarily work for other types of sensory or cognitive disabilities [53,54,55,71]. The CSA/ASC B651:23 has added new requirements for minimum illuminance for pedestrian routes, operating controls, signs, and ramps stemming from research data. Although specifying the minimum illuminance is an important new development, solely is found not sufficient to address the needs of those with low vision or cognitive disabilities [53,54,55].

Reviewing the literature indicated that almost 57% of the research on accessibility for people with visual impairments focuses on exterior circulation and amenities, while approximately 36% of the studies evaluate the overall accessibility of the built environment, as depicted in Figure 7. Within these studies, the primary focus was on accessible routes, which account for 36% of the sample reviewed. Navigation and wayfinding are one of the most evolving and progressing topics in current research, whether indoors or outdoors [26,42,44]. However, many studies did not involve human participants [26,44]. The lack of research in this field resulted in the lack of quantifiable and measurable parameters necessary for the development of robust guidelines. Although the recent CSA/ASC B651:23 standard included new clauses aimed at improving navigation experiences for people with visual impairments, such as “luminance (colour) contrast”, “floor or ground surfaces”, and “direction tactile walking indicator surfaces”, these guidelines lack quantifiable measures, particularly relevant to surface characteristics. Since people with visual impairments often depend on mental maps created from environmental cues, establishing standardized guidelines becomes challenging due to varying personal needs and preferences. This variability was highlighted in a reviewed study, where participants demonstrated diverse preferences in their wayfinding cues [43]. The discrepancies in perspectives and needs of participants complicate the development of standardized wayfinding guidelines.

Research on emergency provisions is significantly limited, which represents only 7% of the reviewed sample. This research gap may be attributed, in our opinion, to the significant influence of social and psychological factors, such as fear and anxiety. It is difficult to integrate social and behavioural factors within accessibility standards guidelines, especially given the diverse range of impairments. A one-size-fits-all solution is ineffective in this case.

Additionally, research on pedestrian infrastructures is found to be lacking. For instance, within the sample reviewed, 14% addressed pedestrian crossings. Such research must account for the complexities of pedestrian infrastructures and the diverse behavioural factors and needs of people with a wide spectrum of visual impairments.

7.3. Sensory/Hearing Disabilities and the Built Environment

There is a significant lack of research relevant to accessibility for people with hearing impairments, as depicted in Figure 2. Figure 8 reveals that most research has focused on evaluating the overall accessibility, in particular, indoor environments [56,57,58], representing 80% of the sample reviewed. The common research method utilized in these studies involved site visits or observational walkthroughs with a few participants, focusing on spatial proximity to facilitate signing communication and safety. Moreover, even in studies involving people with various disabilities, the focus was found to be predominantly on mobility disabilities [40,53]. Additionally, as shown in Figure 3, recruiting individuals with hearing impairments in research studies poses a real challenge, with most studies involving a maximum of 1 to 5 participants. This limitation can lead to personal preferences influencing the findings, thus creating a bias that can adversely impact the development of accessibility standards intended to address the needs of all people with hearing disabilities.

Built environments frequently lack auditory cues and supportive communication systems for individuals with hearing impairments. The CSA/ASC B651:23 has integrated many improvements into guidelines related to acoustics and communications, which could benefit people with hearing impairments. However, many of these improvements are merely recommendations that lack specifications. For example, clause 4.7.3 (Acoustics) recommends designing all environments to be sound controlled without providing specifics. The lack of comprehensive research in this field is preventing the standard development [53,71]. Additionally, visual and other communication formats are barely addressed. The challenge can be attributed to the lack of evidence-based scientific research addressing these needs [53]. This gap was acknowledged in a study on the accessibility of information kiosks, where participants highlighted the lack of communication formats aside from voice [47,55,71].

7.4. Cognitive/Intellectual Disabilities and the Built Environment

Given the diverse spectrum of cognitive/intellectual disabilities, establishing unified requirements to address the unique needs of individuals within accessibility standards presents unique challenges. The CSA/ASC B651:23 offers some recommendations addressing “functional and cognitive barriers”, “environmental intolerances” relevant to air quality and ventilation, and “acoustics”. However, these recommendations remain subjective to personal interpretation, differing from one person to another. This lack of accessibility provisions is further intensified by limited research in this field. Unfortunately, advancing these standards will remain a real challenge without data-driven studies and feedback from those with lived experiences. As expected, most of these attempts primarily focus on social and psychological aspects, which are hard to translate into measurable requirements due to the wide spectrum of disabilities encompassed within this category, each having its own unique needs. Although these aspects are important to consider and cannot be isolated, they should be accompanied by more reliable and measurable research approaches. This issue is compounded by the predominance of “medical” models in research, emphasizing an individual’s adaptation to the environment, rather than the “social” models, advocating for environmental adaptations to accommodate people with disabilities [61,65,66].

In terms of research areas, few studies addressed navigation as it represents a real challenge for people with cognitive/intellectual disabilities, representing 11% of the reviewed studies, as shown in Figure 9. Wayfinding is particularly challenging for these individuals due to difficulties obtaining and processing information and a lack of spatial awareness. Accessibility standards need to provide clear guidelines for those with cognitive/intellectual disabilities. Nearly 44% of the reviewed sample of research studies focused on emergency provisions, as it represents a safety concern beyond accessibility issues [59,60,61].

The other 44% of the research evaluated the overall accessibility of spaces and facilities. Research on people with cognitive/intellectual disabilities falls within “medial/social” and “engineering” silos. Additionally, these studies often focus on specific disabilities, such as dementia [65] or autism [66], which explains why the research does not effectively contribute to the advancement of accessibility standards. Focusing on the “medical/social” symptoms of a specific disability might contradict the needs of the other, making it challenging to establish standardized requirements.

8. Conclusions and Recommendations

Comparing research on accessibility in built environments for people with disabilities in peer-reviewed journals and conferences with the development of accessibility standards has confirmed the obvious and revealed the challenges associated with developing accessibility standards. Developing accessibility standards is found to be driven by data from evidence-based research. The diversity and range of impairments, the interactive and potential adverse effects of solutions provided to mitigate accessibility barriers for people with disabilities, and the complexity of medical and social factors/models developed to study people with disabilities pose an unmeasurable multi-discipline problem that has hindered if not halted the research on accessibility for people with sensory and cognitive/intellectual disabilities. The following conclusions are drawn from this comparative analysis:

• Half of the studies reviewed were on accessibility for people with physical disabilities, a clear indication that visible accessibility barriers are far more researched in comparison to hidden barriers.
• Approximately 50% of the studies employed focus groups, interviews, and survey questionnaires instead of data-driven research.
• Research pertaining to people with physical and visual disabilities dealt mostly with exterior circulation and amenities, and seldom with vehicular access.
• A notable gap in research addressing indoor environments is deduced for people with hearing impairments.
• Recruiting participants with hearing impairments appears to be very challenging, as most research studies included only 1 to 5 participants.
• Most of the research pertaining to people with cognitive/intellectual disabilities follows medical models whose findings are not easily adapted/employed to enhance the development of accessibility standards.

Accordingly, the following recommendations are proposed to advance the development of accessibility standard for the built environment:

• To properly research the needs of people with physical, sensory, and cognitive/intellectual disabilities, a multi-discipline team comprising engineering, medical, and social professionals is needed.
• To address the low participation of people with disabilities, a specific communication protocol must be developed that enables the engagement of people with sensory and cognitive/intellectual disabilities and so that their needs are properly addressed.
• Research funding must target projects that address the gaps in the state of knowledge, add to the development of accessibility standards, are scientifically sound, and include statistical representation of people with different disability types.