Search Results (11)

This study investigated the impact of converting High Occupancy Vehicle (HOV) lanes to High Occupancy Toll (HOT) lanes on fundamental traffic flow characteristics, focusing on speed, density, and flow relationships. A 25-mile HOV corridor along I-24 Westbound in Nashville, Tennessee was evaluated using both microscopic simulation via VISSIM and data-driven machine learning through a Multi-Layer Perceptron (MLP) neural network. Four operational scenarios were assessed: (1) HOV lanes without enforcement, (2) HOV lanes with effective occupancy enforcement, (3) HOT lanes with limited access points, and (4) HOT lanes with intermediate access points. Flow-density and speed-flow relationships were modeled using Greenshields theory to extract key traffic performance thresholds including free-flow speed, jam density, and maximum flow. Results indicate that while free-flow speeds were generally consistent across scenarios (ranging from 71 to 80 mph), HOV and HOT lanes exhibited higher values compared to general-purpose lanes. Capacity increases were observed following HOV-to-HOT conversions, especially when intermediate access points were introduced. The MLP neural network successfully replicated nonlinear flow relationships and predicted maximum flow near 2000 vph with a jam density of approximately 215 vpmpl—values that closely matched simulation outputs. Both the VISSIM and MLP-derived diagrams demonstrated curve shapes and capacity thresholds that were highly consistent with Highway Capacity Manual (HCM) standards for freeway segments. However, slightly higher thresholds were observed for HOV/HOT lanes, suggesting their potential for improved operational performance under managed conditions. The integration of simulation and machine learning offers a robust framework for evaluating managed lane conversions and informing data-driven policy. Beyond the scenario-specific findings, the study demonstrates an innovative hybrid methodology that links detailed microsimulation with an explainable neural network model, providing a concise and scalable approach for analyzing managed-lane operations. This combined framework highlights the contribution of integrating simulation and AI to enhance the analytical depth and practical relevance of traffic flow studies. Full article

Exposure therapy approaches are recognized as effective treatments for specific phobias; however, certain phobias, such as fear of driving on urban highways, present unique challenges in order to expose the patient to the triggering stimuli in a safe, accessible, and controlled manner. In this context, we developed a virtual reality (VR) computerized driving simulator based on a local urban highway, and an accompanying clinical protocol to provide exposure therapy for patients with observed fear of driving on urban highways. We recruited eleven patients for this pilot study, where safety and tolerability as well as clinical and functional improvement were explored. We found that the driving simulator was safe and well tolerated by patients, with a notable 82% of patients successfully completing in vivo exposure, and there being a consistent trend in reduced anxiety scores using standardized testing. Nine patients successfully engaged in live exposures in a real freeway after participating in this VR-based exposure therapy protocol. The creation of an immersive and realistic VR environment based on a local urban highway for treating this phobia proved feasible and well-tolerated by participants. The intervention’s ability to engage patients who might otherwise have avoided traditional exposure therapies is noteworthy. Future research should aim to replicate this study with a larger and more diverse sample to enhance the generalizability of the findings. Full article

The use of dedicated lanes, known as managed lanes (MLs), on freeways is an established traffic management strategy to reduce congestion. Allowing automated vehicles (AVs) in existing MLs or dedicating MLs for AVs, referred to as AVMLs, has been suggested in the literature as a tool to improve traffic operation and safety performance as AVs and driver-operated vehicles (DVs) coexist in a mixed-vehicle environment. This paper focuses on investigating the safety impacts of deploying AVMLs on freeways by repurposing general-purpose lanes (GPLs). Four ML strategies considering different lane positions and access controls were implemented in a traffic microsimulation under different AV market adoption rates (MARs) and traffic demand levels, and trajectories were used to extract rear-end and lane change conflicts. The time-to-collision (TTC) surrogate safety measure was used to identify critical conflicts using a time threshold dependent on the type of following vehicle. Rates of conflicts involving different vehicle types for all ML strategies were compared to the case of heterogeneous traffic. The results indicated that the rates of rear-end conflicts involving the same vehicle type as the lead and following vehicle, namely DV-DV and AV-AV conflicts, increased with ML implementation as more vehicles of the same type traveled in the same lane(s). By comparing the aggregated conflict rates, the design options that were deemed to negatively impact traffic efficiency and capacity were also found to negatively impact traffic safety. However, other ML options were found to be feasible in terms of traffic operation and safety performance, especially at traffic demand levels below capacity. Specifically, one left-side AVML with continuous access was found to have lower or comparable aggregated conflict rates compared to heterogenous traffic at 25% and 50% MARs, and, thus, it is expected to have positive or neutral safety impacts. Full article

The freeway is a continuous flow facility that improves the accessibility and operational efficiency of the road network. However; freeway merging areas are accident-prone areas. In order to investigate the reasons for the high occurrence of accidents in merging areas, this paper considers the dynamic nature of traffic conflicts, constructs a sequence model of merging conflicts with Time Difference to Collision (TDTC) as the index, and implements automatic identification of merging conflicts based on the LightGBM algorithm. A UAV was used to collect vehicle trajectory data at the Guanghe Freeway in Guangzhou to verify the accuracy of automatic identification, with an accuracy rate of 91%. The results show that the most important feature of severe conflicts is the choice of the merging position. In addition, the most important feature of general conflicts is the standard deviation of speed before merging. Lastly, the most important feature of minor conflicts is the longitudinal speed difference between the ramp and mainline vehicles. Full article

Ramps provide entrances and exits for residents to conveniently use the freeway service. Due to the high construction cost and geometric design requirements, the decision of ramp locations involves a trade-off between multiple influencing factors, such as accessibility, safety, efficiency, construction costs, etc. This study proposed a methodology for optimizing freeway ramp placement in an effort to improve freeway accessibility. The freeway ramp locating problem was formulated as a bi-objective optimization model. Two objectives were pertinent to the reduction of total social costs: the minimization of total travel cost and minimization of total construction cost. To reflect the safety concern of ramp locations, the frequency of lane changes around the ramps and the minimum spacing between ramps were constrained. We developed an exact solution method based upon dynamic programming to solve the proposed model. Finally, a case study of the Beijing–Hong Kong–Macau Expressway within Henan Province, China, was conducted to verify the effectiveness of the proposed model and solution method. Full article

Truck platooning is emerging as a sustainable means of transporting goods and commodities to destinations. Platooning optimizes road space and contributes to reducing freight truck emissions. However, there has been limited research on freight truck platoon accessibility to the destination that is often necessary to understand the impact of routes on which platoon is deployed. This study develops an analytical formulation for platoon accessibility by considering the possibility of the detour of trucks forming a platoon. Analyses with four prominent interstates in California, CA, USA, show that accessibility with truck platooning on select lengths of the I-5 continues to increase for about an initial 165 miles, attains a maximum there, and starts to drop after. The other three freeways, I-10, I-405, and I-710, show a continuous increase in accessibility for their lengths and the number of ramps considered. The findings can have significant implications in determining the selection of freeway routes that could be regarded as facilitators for a truck platoon. Full article

PM_2.5 is an air pollutant that is widely associated with adverse health effects, and which tends to be disproportionately located near low-income communities and communities of color. We applied a community-engaged research approach to assess the distribution of PM_2.5 concentrations in the context of community concerns and urban features within and around the city of Santa Ana, CA. Approximately 183 h of one-minute average PM_2.5 measurements, along with high-resolution geographic coordinate measurements, were collected by volunteer community participants using roughly two dozen low-cost AtmoTube Pro air pollution sensors paired with real-time GPS tracking devices. PM_2.5 varied by region, time of day, and month. In general, concentrations were higher near the city’s industrial corridor, which is an area of concern to local community members. While the freeway systems were shown to correlate with some degree of elevated air pollution, two of four sampling days demonstrated little to no visible association with freeway traffic. Concentrations tended to be higher within socioeconomically disadvantaged communities compared to other areas. This pilot study demonstrates the utility of using low-cost air pollution sensors for the application of community-engaged study designs that leverage community knowledge, enable high-density air monitoring, and facilitate greater health-related awareness, education, and empowerment among communities. The mobile air-monitoring approach used in this study, and its application to characterize the ambient air quality within a defined geographic region, is in contrast to other community-engaged studies, which employ fixed-site monitoring and/or focus on personal exposure. The findings from this study underscore the existence of environmental health inequities that persist in urban areas today, which can help to inform policy decisions related to health equity, future urban planning, and community access to resources. Full article

Accessibility is important for road network planning and design, especially the accessibility of freeway entrances and exits, which reflects the convenience of travelers using freeways and the rationality of the connection between urban roads and freeways. Based on the path information of navigation map software, a new comprehensive travel impedance model to dynamically analyze the accessibility of freeway entrances and exits was proposed. The dynamic accessibility of freeway entrances and exits in Zhengzhou was studied using the proposed comprehensive impedance model, and the calculation results were analyzed. The accessibility of freeway entrances and exits is characterized by dynamic changes; the accessibility during the off-peak evening period is the highest, while that during the morning peak period and evening peak period is lower. The results of the comprehensive impedance model are roughly consistent with reality. From a location perspective, regardless of the period of time, the accessibility of freeway entrances and exits in the central and surrounding areas of Zhengzhou is always at a lower level, and during the off-peak afternoon period, the accessibility of the eastern part of the city is notably higher than that of the western part. Additionally, the accessibility of freeway entrances and exits is closely related to the traffic status of the road network and the characteristics of regional land use. The information can provide feedback for planning road networks and provide a reference for road network planning and traffic facility design. Full article

Culture is frequently used as a means of promoting sustainable urban development. Indeed, in many areas across Europe, cultural and recreational routes or clusters have so far been utilized in order for urban regeneration and structural reconstruction to be pursued. Such routes have been developed in Greek cities as well, e.g., in the cities of Volos, Thessaloniki, and Athens. In the Greek capital, Athens, a couple of axes are actually recognized as cultural ones. Andreas Syngrou Avenue, initially designed as a six/eight-lane freeway located at the heart of the Athens metropolitan area, is one distinguished example. By focusing on this axis as a cultural route/cluster, the goal of this article is to elaborate on smart and sustainable mobility patterns for strengthening its cultural/recreational identity and increasing its attractiveness. To accomplish this goal, critical problems confining citizens’ mobility and access to various cultural landmarks in this area are identified and are properly dealt with, stressing the importance of sustainable mobility in relevant cultural planning endeavors. Based on the study and an assessment of the current state of this route (land uses, traffic loads, design qualities, and environmental affordances), a sustainable mobility proposal is provided in order for a master plan that enhances and develops the cultural function and identity of this route. Full article

There is growing agreement that refueling station location plans that aim to encourage public adoption of alternative fuel vehicles (AFVs) should include sites near freeways in urban areas. Little is known, though, about the refueling behavior of early AFV adopters in these locations, which can involve travel on complex and congested roadways. To address this, an intercept travel survey collected data from 158 drivers of compressed natural gas (CNG) vehicles who refueled at CNG stations near freeways in greater Los Angeles, California. Results show that these stations met refueling demand from across the majority of the metropolitan area, and the distribution of local and distant refueling demand was consistent except for the downtown station. Drivers also considered these stations to be safe and accessible. Nearly half of drivers did not include another local stop in conjunction with their refueling trip that required leaving and returning to the freeway. These respondents refueled on longer trips with lower fuel tank levels, while refueling at the station that minimized deviation. Refueling downtown negatively influenced refueling in this manner. These findings should be considered when recommending station sites near freeways in future AFV infrastructure plans. Full article

Current studies on measuring the accessibility of medical services for the elderly (AMSE) have ignored the potential competition among supply and demand and the distance decay laws. Hence, an enhanced two-step floating catchment area (E2SFCA) method (i.e., the road network-based Gaussian 2SFCA method) is proposed to calculate AMSE scores after considering different types of roads, including urban rail transit, freeways, major roads, minor roads and rural roads. Based on the first National Geographic Conditions Monitoring (NGCM) data, this study took Wuhan, China, as a case study and assessed the variation of AMSE using two different threshold times (i.e., Platinum Ten and Golden Hour). Next, global (i.e., sensitivity and hot spot analysis) and local analyses (i.e., three regional area internal comparisons) of AMSE scores were conducted to accurately identify details in the variation of spatial accessibility. It was observed that the E2SFCA method could be easily applied to measure AMSE. The results showed that 48.63% of the elderly population in Wuhan had a higher or the highest level of medical accessibility in “Platinum Ten”, while 72.97% had a higher or the highest level in the “Golden Hour”, and hot spots of AMSE scores were located in central urban areas and presented an enclosure structure using both threshold travel times, which could provide guidance to governments or planners on issues of spatial planning and identifying elderly medical services shortage areas. Full article