An Impact Assessment of Speed Humps’ Geometric Characteristics and Spacing on Vehicle Speed: An Overview

Abstract

This review examines the effect of geometric properties and the spacing of road humps on vehicle speed and noise, with a particular emphasis on South Asian contexts, especially Malaysia. Road humps are widely used traffic-calming devices designed to reduce vehicle speed and enhance road safety. The effectiveness of these measures is strongly influenced by parameters such as height, width, profile, and placement intervals. While the geometric optimization of humps generally improves speed-reduction outcomes, several studies indicate that braking and acceleration at humps can lead to increased traffic noise, particularly in residential and high-density areas. This review also explores design strategies and material choices (e.g., asphalt use, sinusoidal profiles) that may help mitigate noise impacts. Overall, a balance between speed control and noise management is necessary to ensure both safety and community acceptance.

1. Introduction

Transportation affords massive socio-economic benefits to all contemporary societies. Specifically, road transportation is the backbone for most of the advanced nations, as other modes of transport are either in their initial phase or do not exist. However, road transportation also has its shortcomings, and road crashes are one of the most significant corollaries of road transportation. Road traffic collisions are the 8th leading cause of death across all age groups and lead to the deaths of children and young adults aged 15–29 years [1].

Human error is identified as a considerable contributor to broadside crashes, while road and vehicle conditions can contribute to driver errors and sometimes be the primary cause of RTCs. Although road conditions are not the leading cause of crashes, maintaining good road quality is a cost-effective measure that can reduce crash risk [2]. According to recent WHO statistics, human error is responsible for around 94% of road traffic accidents. Vehicle-related factors, such as mechanical failures, contribute to 2–5% of crashes, while road conditions (including surface quality, design, and maintenance) account for about 2–3% of accidents [1]. However, as noted by Elvik in 2024, not all human errors can be avoided; rather, only those causally related to modifiable or internally controlled risk factors, such as road design or enforcement, would yield policy remedy. His work would advise not attributing too much of the accident occurrence to human behavior without cognizance of the structural and contextual constraints that may be outside the control of the driver [3]. As indicated in

Table 1. Causes of road traffic crashes (%) in Malaysia.

Human Error	Road Conditions	Vehicle Conditions	Other Factors	Country/Agency	Reference
80.6	13.2	6.2	-	Malaysia	Mohamed et al. [4]
29	64	7	-	Malaysia	Tan et al. [5]

, the magnitude of impact these factors have varies significantly. For instance, Mohamed et al. [4] found that human error accounted for 80.6% of road crashes in Malaysia using national-level data provided by the Malaysian Institute of Road Safety Research (MIROS), negating this comprehensive use of data across a wide range of road types and conditions. Tan et al.’s [5] study reported that road conditions accounted for 64% and human factors only for 29% of crashes in a localized study of a 10 kilometer section of the Pan Borneo Highway in Sarawak. This discrepancy stems from the study context, methods, timeline, and geographical context, and while this does not identify a clash, it supports contextual relevance in any traffic crash analysis.

Speed management has become a critical risk-causing agent over the past century for motor-vehicle crashes, influencing the degree of injury to a greater extent [6,7], leading to the increased installation of horizontal and vertical traffic-calming devices, such as speed humps, gateways, speed bumps, and speed cushions. These devices encourage drivers to adjust their speed according to the type of road. The traffic-calming approach has arisen predominantly as a safety requirement for society. This approach significantly contributed to augmenting road safety by promoting a reduction in driving speed [8]. However, traffic-calming measures do not always ensure that drivers adhere to the speed limits. As a result, researchers have focused on assessing the effectiveness of these devices, considering factors like their size (height, length, gradient, and radius) and shape. Their effectiveness is evaluated by analyzing their impact on speed reduction and the reduction in accident rates [9].

Speed humps are a common traffic-calming strategy for mitigating crash frequency and crash severity, especially in residential areas and around pedestrian traffic [10]. Ideally, they are designed to reduce vehicle speed to between 25 and 30 km/h, which increases pedestrian safety and decreases injury risk in the event of a crash [11]. Nevertheless, research has suggested that incorrectly designed speed humps, based on their height, spacing, or signage, can induce erratic driver behavior including sudden braking and swagging, aggressive speeding, or lane shifting, all of which can increase the likelihood of rear-end collisions and vehicle damage. For example, some recent studies on poorly designed, inadequately placed or inaccurately spaced speed humps have resulted in disruptions of the traffic flow, an unsafe driving space, and increased crash risk associated with arterial and urban roadways. Safety concerns express the need for design compliance and standardization to promote positive outcomes while reducing risk factors to road safety [12,13].

This review examines the geometric dimensions and spacing of speed humps in urban residential contexts with a primary focus on Malaysia while also exploring wider literature internationally. The intended focus on South Asia, in particular Malaysia and the region, adds a degree of novelty to the literature that is, as it stands, overwhelmingly Western-centric. The speed-flow capacity limitations of road infrastructure, mixed traffic environments, and local differences in enforcement capacity that are common among South Asian countries suggest the need for more localized origin-specific evidence, which this study aims to provide.

In particular, it examines the implications of various design features (length, height, width, and spacing) for vehicle speed and noise creation across diverse vehicle classifications and contexts. The existing literature provides a fragmented picture of speed humps often without the benefit of a cohesive conceptual framework. Therefore, this review proposes a novel classification of speed hump impacts based on three key dimensions: (i) road context (urban, arterial, school, etc.), (ii) vehicle type (passenger car, motorcycle, heavy vehicle, etc.), and (iii) regional differences in road infrastructure context and governance implementation. Although various studies have considered the performance of speed humps in specific contexts such as urban or residential settings, few have taken a comprehensive review that considers the interaction of geometric dimensions and spacing, vehicle type, and road context across space and region. This review is unique, as it provides a comparative perspective bringing together observations across countries such as Malaysia, India, Spain, Egypt, and Italy to help identify similarities and differences in practices. Although the study is primarily a review of speed hump designs, it did provide a new three-tier classification system which considers regional differences in regulatory standards, in urban planning approaches and regulatory enforcement, and in driver behavior. Such a multi-faceted review provides a clearer picture for generating local responses that are more regionally appropriate; Craig provides a review that is more globally relevant.

Furthermore, while previous studies have looked at literal reductions in vehicle speeds, there has been less examination of the interaction between vehicle type, hump geometry, and noise impact, especially in urban Southeast Asia contexts. Further, there is a gap in the literature regarding standardized guidelines for the installation of humps, especially in Malaysia where enforcement can be inconsistent. This review aims to provide context-sensitive, evidence-based design recommendations by consolidating international and local evidence supporting speed management while limiting inadvertent negative consequences such as noise pollution or traffic congestion. The specific objectives of this review are as follows:

(i)

To investigate how the geometric characteristics (length, height, and width) of speed humps affect vehicle speed in urban residential areas;

(ii)

To assess how the spacing between speed humps influences vehicle speed; and

(iii)

To evaluate the residents’ perceptions regarding the effectiveness of road humps in reducing traffic noise levels.

2. Materials and Methods

This narrative review examines the geometry and spacing of speed humps to determine their functionality to reduce vehicle speed and sound. The review contains literature from 2014 to 2025. A systematic search using four academic databases: Scopus, Web of Science, ScienceDirect, and Google Scholar, was established to ensure articles could be tracked and reproduced. The search strategy involved combinations of the following key terms: “road humps”, “geometry”, “vehicle speed”, “spacing” and “traffic calming” laws, as well as applying search filters to titles and abstracts so the outcomes would include studies that are directly related to the topic of study.

A rough estimate of initial publications was approximately 120 documents. The documents were included based on the following criteria: (i) peer-review-based; (ii) available in English; (iii) available for free access or accessible through institutional means; (iv) explicitly recognized the geometric design (e.g., height, width, profile, and spacing) of speed humps and even measured or simulated their effect on speed, noise, and road safety. Studies were excluded if they were conference abstracts without a full paper, had no information on vehicular traffic-calming measures, or lacked empirical data or a simulation model. After using the inclusion/exclusion criteria and removing duplicates, 17 relevant studies were identified. The 17 relevant studies cover a diverse spectrum of countries and urban contexts accentuating the multiplicity of approaches and findings identified in speed hump implementations. In order to portray clarity and chronological order, the studies were arranged in

Table 2. Summary of reviewed studies.

Author(s)	Year	Country	Research Goals	Methods	Key Findings
Zainuddin, N.I.; Adnan, M.A.; Md Diah, J. [14]	2014	Malaysia	To optimize the geometric design of speed humps in residential streets	Case study, simulation modeling	Proposed optimal designs for safety and comfort; improper designs caused safety concerns.
Bachok, K.S.R.; Hamsa, A.A.K.; Mohamed, M.Z.; Ibrahim, M.A. [15]	2017	Malaysia	To explore the theoretical impacts of road humps on traffic noise and residential well-being	Theoretical review and conceptual discussion	Indicated that traffic noise mitigation through road humps can improve resident well-being.
Kiran, K.R.; Molugaram, K.; Sandeep, M. [16]	2020	India	Analyze speed profiles at speed humps with varying dimensions and simulate LOS using VISSIM (version 2018).	Speed profile analysis; simulation with VISSIM (version 2018) software	Speed hump dimensions significantly affect speed profiles; simulation validated impact on LOS.
Distefano, N.; Leonardi, S. [12]	2019	Italy	Evaluate the benefits of traffic calming on vehicle speed reduction.	Field measurement before and after traffic calming	Traffic-calming devices significantly reduce speeds, improving safety.
Shwaly, S.A.; El-Ayaat, A.; Osman, R. [17]	2024	Egypt	Assess the effects of speed humps on travel time, safety, and environment.	Empirical measurement of delays, emissions, and safety	Closer hump spacing reduces speeds but increases delays, fuel consumption, and environmental impact.
Obregón-Biosca, S.A. [18]	2020	Spain	Evaluate externalities of speed humps/tables on speed, emissions, and fuel consumption.	Field measurements and statistical analysis	Speed humps reduce speed but increase emissions and fuel consumption due to stop–start driving.
Mashrosa et al. [19]	2020	Malaysia	Evaluate the effectiveness of road humps in reducing vehicle speeds on a university campus.	Before-and-after speed measurements at multiple campus sites	Average speed reductions of 15–20 km/h; high compliance when humps are well-signed and marked.
Gonzalo-Orden et al. [20]	(2018)	Spain (urban areas)	Assess the impacts of various traffic-calming measures across different Spanish cities.	Field speed surveys, comparative analysis	Raised crosswalks and lane narrowing reduced speeds by 10–15%; effectiveness varied by urban context.
Solowczuk [21]	(2019)	Poland (Tempo-30 zones)	Measure speed reductions due to vertical vs. horizontal calming measures in Tempo-30 zones	Speed monitoring before/after interventions	Vertical devices (humps, raised junctions) were more effective (speeds < 30 km/h) than horizontal deflections.
Tan, S.L.; Kabit, M.R.; Johnson, O.A. [5]	2021	Malaysia (Sarawak)	To evaluate crash-prone areas along the Pan Borneo Highway	Case study, spatial analysis	Identified multiple high-risk crash segments requiring targeted interventions.
Badiger et al. [22]	(2022)	India (Bengaluru arterial roads)	Evaluate the effectiveness of various speed-calming measures on arterial roads.	Field speed data collection, comparative evaluation	Trapezoidal humps reduced speeds by up to 35%; rumble strips had a < 15% reduction.
Raccagni et al. [23]	(2024)	Italy (Brescia)	Investigate how urban road characteristics influence vehicle speeds	GPS-based speed logging, statistical analysis	Lane width and segment length heavily influenced speeds; traditional calming had context-dependent impacts.
Obregón-Biosca [18]	(2020)	Spain	Quantify externalities (emissions, fuel use, speed) of speed humps vs. tables.	Emission modeling, speed measurement	Speed humps: 50–75% speed reduction; speed tables: 10–65%; higher emissions and fuel use at very low speeds.
Abdulmawjoud et al. [13]	(2021)	Iraq (Mousal City arterial)	Model traffic flow parameters at traffic-calming installations on arterial roads	Traffic simulation, field calibration	Properly spaced humps improved the Level of Service; poorly designed humps caused delays and driver frustration.
Mohanty et al. [24]	(2021)	India (Bhubaneswar)	Examine the operational effects (speed profiles) of speed breakers on major urban roads.	Field speed measurements at multiple hump locations	Speeds dropped from ~33 km/h 20 m before humps to ~9.8 km/h at humps; a significant deceleration zone was identified.
Gamlath et al. [25]	(2023)	Sri Lanka (residential areas)	Evaluate the relationship between hump geometry, speed reduction, and noise generation.	Combined speed and noise monitoring	Passenger cars: 42% speed reduction; motorcycles: 23.5%; noise increased by up to 4 dB at higher hump heights.

by publication year and geographic origin, and those studies included basic metadata, such as authorship, aims, methods, and findings. This methodology promotes both transparency and the potential for other researchers to replicate the review process in future studies.

3. Results and Discussion

This section provides a structured review of empirical and technical studies about the effectiveness of traffic-calming devices, particularly speed humps. The review is organized thematically to correspond with important factors influencing their performance and public perceptions. It will first investigate the effectiveness of speed humps in reducing vehicle speed and road safety outcomes, then discuss geometric design features such as height, width, and shape, all factors in determining effectiveness. The review will then examine how speed humps spacing and placement influences traffic flow and driver behavior. After examining spacing and placement, there will be a consideration of noise, and other types of nuisance complaints regarding speed humps in residential and other sensitive areas. Finally, public perceptions, acceptability, and policy and urban planning implications will be discussed. Each subsection supports an overall understanding of the multiple considerations related to speed humps.

3.1. Traffic-Calming Measures

Recent empirical research offers a deeper understanding of how traffic-calming devices perform in real-world settings. In Malaysia, Sofi & Hamsa (2025) [26] conducted field noise measurements and found that while road humps reduced vehicle speeds by approximately 40%, average noise levels increased by 3–5 dB(A), eliciting negative public reactions in over 60% of households. Gamlath et al. in 2023 [25] evaluated four hump profiles in Sri Lanka using speed and noise sensors combined with VISSIM simulation. They reported an average speed reduction of 33.9% across all vehicles, with passenger cars slowing by 42%, but found noise exceeded permissible limits by 2–4 dB(A). Haroon et al. (2025) [27] quantified noise impacts of various devices, showing that vertical features (like humps) elevated average noise by 2.5 dB compared to baseline.

Case studies from Europe and Eastern Europe reinforce these results. Bugayov et al. (2024) [28] reported that in Kharkiv, Ukraine, installing vertical humps reduced peak speeds by nearly 20 km/h on local streets, but also led to a 7 s delay per hump and a 1-level drop in LOS. Ambros et al. (2023) [29], reviewing best global practices, noted that while humps consistently cut speeds by 15–30%, public acceptance hinges on post-implementation engagement. Cantisani et al. (2023) [30] highlighted design elements, like consistent signage, tactile paving, and visual cues, that improved compliance and reduced user friction. Together, these studies demonstrate that traffic-calming measures, especially vertical humps, achieve substantial speed reductions but also tend to increase noise and travel delays. Crucially, their success depends on context-specific design, signage, and community involvement, not merely device installation.

Recent research helps us understand how traffic-calming devices operate in the real world. In Malaysia, Sofi & Hamsa in 2025 [26], conducted measurements of field noise and found that road humps reduced vehicle speeds by approx. 40%, but increased the average noise level by 3–5 dB(A) and had negative community responses from more than 60% of households supported. In 2023, Gamlath et al. [25] assessed four hump profiles in Sri Lanka, using speed and noise sensors, alongside VISSIM simulation, reporting an average speed reduction of 33.9% for all vehicles and 42% for passenger cars, but the noise levels were 2–4 dB(A) above the acceptable level. Haroon et al. in 2025 [27], measured noise impacts from various devices and showed noise levels from vertical features (humps) increased the average noise by an additional 2.5 dB compared to baseline noise levels. Case studies from Europe and Eastern Europe corroborate these findings. In 2024, Bugayov et al. [28] reported that road humps implemented in Kharkiv, Ukraine reduced peak speeds by nearly 20 km/h on local roads, but resulted in 7 s of waiting time per hump and a single-level reduction in LOS. Ambros et al. in 2023 [29], identified global best practices and noted that traffic humps consistently reduce speeds by 15–30%, while residents’ acceptance of traffic calming is affected by engagement effectiveness post-implementation.

3.2. Traffic-Calming Measures in Malaysia

Malaysia has faced significant losses due to road crashes, prompting concerned efforts to improve road safety. The Malaysian Institute of Road Safety Research (MIROS) plays a key role in this initiative, focusing on road user behavior, road engineering, and vehicle safety. The Malaysian Road Safety Plan 2022–2030 includes strategies like enhancing Road Safety Education (RSE) programs, which MIROS revised and piloted in 2016 for primary, secondary, and preschool students [4].

The Malaysian Highway Planning Unit categorizes traffic-calming measures as:

• Vertical measures which affect the speed of motorists via the vertical deflection of motor vehicles crossing over the devices.
• Horizontal measures which affect the speed of the motorist via the lateral deflection of the motor vehicle traversing the device.

Among both measures, the Highway Planning Unit of Malaysia has also endorsed vertical measures as more effective than horizontal ones. Consequently, this research focuses on speed humps, as this device is the most common initiate of vertical measure in Malaysian residential zones [31]. Figure 1 depicts the further classification of vertical and horizontal traffic-calming measures based on the guidelines of the highway planning unit. Among the various traffic-calming devices implemented in Malaysia, road humps have emerged as the most prevalent and effective vertical measure. The following section provides a more detailed look at the design, application, and impact of road humps.

3.3. Road Humps

A road hump, also known as “pavement undulation”, is a raised mound in the roadway that stretches across the travel lane perpendicular to the traffic stream. Road humps are commonly used in residential areas, including Malaysia, to reduce vehicle speeds and traffic noise. Research shows that road humps are effective in lowering vehicle speeds and noise levels, with the height of the humps influencing these effects. Taller road humps are good at reducing vehicle speeds; however, they may also contribute to higher noise levels as drivers will brake suddenly and accelerate rapidly when approaching and leaving the road humps, which results in larger fluctuations in audible noise in residential areas in Malaysia [15].

Many studies have confirmed the effectiveness of road humps in speed reduction. For example, Kiran et al. [16] showed a reduction in speed from 49% to 59% for two- and four-wheeled vehicles, and 29% to 61% for light commercial vehicles along a road in India. A similar study by Werner [32] found that after road humps were installed on two streets in the USA, the 85th percentile speed of two-wheeled vehicles dropped by 15.8%, and four-wheeled vehicles by 36.6%. The number of vehicles driving at speeds below 25 mph increased significantly at both locations. It is important to note that vertical deflections, such as road humps, can also increase the emissions of atmospheric pollutants and noise if vehicles do not sufficiently reduce their speed while traversing them [12]. While the effectiveness of road humps in controlling speed is well-established, the specific outcomes largely depend on how these humps are designed and implemented. The following section explores the critical design parameters that influence their functionality.

3.4. Road Hump Design

Design Parameters

To provide a clear understanding, we detail road hump design, which involves two main parameters: layout design and geometric characteristics. Layout design parameters integrate spacing between the humps, construction materials, road marking, and signboards, while the geometric parameters consist of length, hump profile, hump width, and hump height [33].

As mentioned above, a speed hump is an elongated region protruding from the roadway, located transversely to the traffic stream, and has distinct design shapes including circular, parabolic, sinusoidal, and trapezoidal (flat-toped) profiles, as presented in Figure 2 [34]. Among the various geometric and layout elements, spacing is particularly influential in determining both safety and environmental outcomes.

The spacing of speed humps is a key factor in affecting vehicle speed, road safety, travel time, fuel usage, and environmental impacts. Research has shown that speed humps that are closely spaced will produce consistent reductions in vehicle speed (41.65% reductions) which increases safety in traffic-calmed portions of the road [17]. However, as spacing increases, their effectiveness diminishes due to vehicle acceleration between humps, leading to inconsistent speed control [35]. As for safety, speed humps reduce the possibility of high-speed collisions, especially in urban areas with high pedestrian traffic, while lower speeds usually produce fewer crashes and less severe crashes [36]. However, closely spaced speed humps will also add significant time delays when traveling (9.31 s per hump) and will increase congestion with density [17,37]. Environmental impacts should be considered too, as frequent vehicle acceleration and deceleration, and frequent speed changes consume excess fuel, resulting in additional fuel consumption for motorcycles (12.07 km) and passenger cars (27.37 km) per 100 km, or 13.73% and 37.74% higher fuel consumption, respectively [17].

In addition, operating at lower speeds, primarily in the range of 0–15 km/h, can increase pollutant emissions, potentially impacting urban air quality. The wrong spacing of humps can also further increase fuel consumption and emissions, thus increasing operational costs [37]. Thus, while speed humps are effective for controlling speed and enhancing safety, their spacing must be strategically optimized to balance these benefits with environmental and efficiency trade-offs. A few recent studies also point in the direction of the greater implications of hump design, not only with speed but with environmental impacts and road safety, overall. Ziolkowski (2015) [38] indicates that speed management methods, including traffic-calming devices, like speed humps, can reduce CO₂ emissions significantly by providing smoother driving patterns. Pérez-Acebo et al. (2020) [39] examine the spacing of vertical traffic-calming devices (like speed humps) to maintain an adequate speed-reduction effect. Majer and Sołowczuk in 2025 [40], conducted a case study of road humps in residential areas to demonstrate that a well-designed series of road humps can reduce vehicle speeds as well as improve safety. They highlight the speed hump design and placement as being of principal importance to optimize traffic-calming effects.

In a study by Molan and Kordani [41], it was evaluated that certain speed hump profiles performed well in reducing vehicle speed and minimizing discomfort. Speed humps can increase vertical forces on vehicles by up to 94%, which can affect passenger comfort, especially on certain hump shapes. Among different types of humps, flat-topped humps were found to be more cost-effective and performed similarly to more expensive shapes like sinusoidal or parabolic humps. The length of the ramp leading up to the hump also influenced its effectiveness.

Similarly, a study conducted on road humps in Skudai, Malaysia, indicated that most of the humps installed did not meet the required design standards. However, well-designed humps can significantly reduce vehicle speeds. Round-top humps slowed down the speed by 46%, while flat-top humps reduced speed by 52%. The study confirmed that road humps, regardless of their type, are effective in reducing vehicle speeds [19]. While international studies provide valuable insights into hump design and performance, it is equally important to examine how these principles are applied in the Malaysian context.

3.5. Road Hump Design in Malaysia

The Malaysian Highway Planning Unit has described speed hump as an elevated portion of the pavement, with the height and traverse length varying from 3.5 to 4 inches and 6.71 to 9.14 m, respectively. But two issues persist in Malaysia, which are very common viz. the lack of standards in the guidelines prescribed for installing the speed humps and variations in preinstalled humps concerning dimensions and spacing. This can put the driver in a dilemma and a general lack of effectiveness [42].

To address these discrepancies, the Standards and Industrial Research Institute of Malaysia (SIRIM) has developed more detailed specifications. According to SIRIM [43], speed humps in Malaysia are categorized by their shape and typically include the following: parabolic, circular, and sinusoidal.

In

Table 3. Road hump standards in Malaysia. Sources: Highway Planning Unit, Ministry of Works (2002) [31]; Standards and Industrial Research Institute of Malaysia (SIRIM, 2009) [43].

Source	Dimension	Spacing	Others
Malaysian Ministry of Works, 2002 [31]	(a) Flat-Top Hump Height: 75 mm–100 mm, Length: 2.5 m–4 m	100m	(1) Vehicle speed between 30 km/h to 60 km/h
	(b) Round-Top Hump Height: 50 mm–100 mm, Length: 3.7 m–4 m		(2) Allowed on district roads, residential roads, access roads, and rural roads
	(c) Sinusoidal Hump Height: 75 mm–100 mm, Length: 3.8 m–4 m		(3) Road geometry: 2-way and 2-lane roads with no curbs.
			(4) Should not be located near road intersections.
SIRIM, 2009 [43]	(a) Parabolic Hump Height: 75 mm–100 mm, Length: 3.7 m–4.25 m	Mentions that a spacing of 90 m to 180 m reduces 85th percentile speeds by 12 km/h to 15 km/h	(1) Construction tolerance of ±3 mm
	(b) Circular Hump Height: 75 mm–100 mm, Length: 3.7 m–4.25 m
	(c) Sinusoidal Hump Height:75 mm–100 mm, Length: 3.7 m–4.25 m

, the Malaysian speed hump regulations as researched by Zainuddin et al. [14] are presented. These regulations were compiled by Zainuddin et al. [31,43] by browsing official documents from the Highway Planning Unit, the Ministry of Works, and the Standards and Industrial Research Institute of Malaysia.

According to suggestions from the study of Bachok et al. [15], in urban localities of Malaysia, the speed humps’ height and length should be 50 mm to 100 mm and 3 m to 4 m, respectively, to achieve the speed limit of 35 km/h. Additionally, Malaysian standards specify location-based restrictions on the application of vertical traffic-calming devices. Vertical devices such as speed humps are discouraged by the Highway Planning Unit and SI-RIM in special cases on arterial roads, intersection locations, and in locations or roads that serve as primary emergency routes or bus routes. Concerns surface with respect to vehicle damage, emergency services response, and driver discomfort [31,43]. Nonetheless, the directives indicate that vertical devices will, indeed, be applied in appropriate locations and that they are context sensitive for the Malaysian traffic environments. Despite the availability of design standards, several challenges persist in practice. Although Malaysian guidelines provide a starting point for safe and effective hump design, there are no enforcement mechanisms in place, and there are local authorities or developers who will install them in a non-standardized manner. In addition, few empirical studies assess how well the different shapes and configurations of humps function in practice. Studies often measure and report such outcomes as speed reduction, but do not provide information about critical factors like road surface conditions, traffic flow, or adherence to design specifications, which are required for replicability and assessment.

3.6. Effects of Road Hump on Traffic Speed

High vehicular speed significantly increases the likelihood and severity of accidents, especially in urban and residential areas. To address this issue, traffic-calming measures, particularly speed humps and raised pedestrian crossings, have been widely implemented to reduce vehicle speed and enhance pedestrian safety [44]. To better understand the role of road humps in speed regulation, several empirical studies have been conducted, assessing their real-world effectiveness.

Empirical Evidence on Speed Reduction

Speed humps are a common intervention globally aimed at mitigating crashes by reducing vehicle speeds. The research shows that they are effective, as many studies confirm reduced injuries and crashes from speed humps. For example, one research study in Spain concluded that construction interventions, such as raised crosswalks and lane narrowing, reduce vehicle speeds in urban areas, but it is important to note that their conclusions are not broadly generalizable [20]. Similarly, studies conducted inside Tempo–30 zones suggest that vertical deflections like speed humps consistently limit speeds below 30 km/h compared to horizontal deflections [21]. In India, trapezoidal speed humps on arterial roads saw a 34.9% reduction in vehicle speed [22]. However, speed humps are context specific. Raccagni et al. (2024) [23] highlight area characteristics (lane width and segment length are much better predictors of vehicle speed than calming) and add that the spacing and characteristics of the local roads are crucial for design outcomes. Their research shows that spacing between speed humps is a major influence on consistent speed reductions. Driver behavior, particularly the changes to vehicle speed when facing the hindrance of speed humps, is substantially affected by road environments such as residential roads, school zones, and arterial roads. A Malaysian field study shows vehicular speeds in the residential area of Kuala Lumpur reduced from about 30 km/h before the hump to below 10 km/h at the hump, with an earlier and gradual initiation of driver deceleration [45]. The same set of authors, Sofi & Hamsa, found that vehicle speeds reduced considerably in the vicinity of the humps and recovered rapidly, indicating fast re-acceleration behavior in familiar residential zones [46]. Conversely, in the streets of Mosul, flat-topped humps were recorded with sudden deceleration of up to 1.2 m/s² and equally quick re-acceleration reaching 1.1 m/s², implying that drivers over these higher-speed or less-regulated corridors tend to show aggressive speed-control traits [13]. Different influences stress the need to include road context in design and placement strategies, since context significantly determines the speed performance of hump geometry and the associated environmental consequences. In support of this, Pérez-Acebo et al. in 2020 [39], recommend a maximum distance of 200 m between vertical deflection measures speed humps to achieve the same speeds over longer sections of road. Shorter distances typically lead to drivers braking and accelerating more, resulting in lower speeds. Wider spacing between speed humps may allow vehicles to speed between humps. Other studies using clustering methods to investigate levels of service confirm that well-designed and well-spaced speed humps lower traffic speeds and risk levels, and poorly designed or poorly spaced speed humps degrade the user experience for any given road user, or worse, result in damage to their vehicle or driver frustration [47]. In studying speed humps in developing countries, issues such as construction or maintenance quality affect speed humps and their designs and spacing. For example, some examples in different studies from India suggest removing speed humps entirely or replacing them with chicanes to produce a more controlled driving environment and improved safety where road humps are. Although the studies make an important point about spacing, these studies ultimately fail to fully address issues surrounding speed hump spacing, or use samples that are either limited in size or geographic diversity; thus, more work needs to be carried out to provide a full understanding of the ideal spacing of speed humps. Beyond placement and spacing, the geometric design of speed humps also plays a critical role in determining how drivers respond to them in terms of speed and comfort [48].

3.7. Effects of Geometric Characteristics of Speed Hump on Vehicular Speed

Numerous studies have been conducted to test the outcome of varying road hump characteristics on motor-vehicle speed. The reduction, although temporary, occurs at a speed of 41–56 km/h (downstream). Gyaase et al. [10] highlighted that there was a notable shift in the severity of injuries following the installation of speed hump devices, as 77% of the fatal, minor, and injury cases were reduced. Moreover, Obregón-Biosca [18] found that the dimensions and contour of speed humps and speed tables have significant impacts on the reduction in vehicle speeds. When all characteristics of speed humps were equalized, it was found that speed humps reduced speed by 50% to 75% and trapezoidal speed tables reduced speed by 10% to 65%, showing that the geometric aspect of traffic calming can be incredibly impactful. Abulmawjoud et al. [13] also examined three types of speed humps installed in Mousal City. Their study found that speed humps significantly reduce the speed of vehicles by 71.6% for flat-topped humps, 66% for double-humped, and 60% for single-humped. Geometric design not only affects speed reduction but also influences other outcomes, such as vehicle noise levels and the varying responses among vehicle types.

In 2023, Berloco et al. [49] performed a detailed quasi-experimental field study in Bari, Italy. They evaluated the effects of three Berlin-style speed cushions with lengths of 2.2 m, 2.7 m, and 3.2 m. Laser-speed measurements were taken from different distance intervals around each cushion, and ANOVA was used to show that all vehicles under speed measurements had reduced speeds to about 13 km/h immediately before and just after the cushion, with cushion length significantly affecting the depth of speed reduction; shorter cushions produced much greater slowdowns. The time of day and baseline traffic conditions also influenced effectiveness. From an experimental aspect, a complement to the existent study on parabolic or flat-topped humps is that a demonstration informs speed moderation, where cushion length and context variables matter. It backs the review’s focus on geometry and placement, particularly in mixed urban settings.

3.7.1. Interaction with Vehicle Type and Noise

Similarly, the study of Gamlath et al. [25] investigated the impact of speed humps’ geometric profile on the noise level and speed of a vehicle. Their findings revealed that the speed of a vehicle reduces as the height of the speed hump increases. The most significant decrease in speed was noted in passenger cars (42.13%), whereas motorcycles showed the least reduction in speed (23.5%).

The geometric characteristics of speed humps, such as height and shape, significantly influence the noise generated by different vehicle types during transit. Research by Gamlath et al. in 2023 [25], indicates that increased hump height leads to greater vehicle deceleration and acceleration, thereby elevating noise levels particularly in passenger cars. These vehicles, which experience a 42.13% speed reduction over humps, produce more pronounced noise peaks due to abrupt suspension compression and engine load changes. In contrast, motorcycles, which exhibit a smaller speed reduction (23.5%), generate relatively lower noise levels. This variation suggests that the interaction between hump geometry and vehicle type is a key factor in environmental noise impact.

Another reason for the perceived noise levels due to speed humps is the ground vibration. Ground vibration is caused by the suspension of the speed humps interacting with the vehicle load and the speed hump parameters [50]. The whole interaction causes resonance and structural vibrations to occur as well, and all of this demonstrates the need to carefully design speed humps to subdue speed, while also reducing noise, especially in urban areas where noise perception is heightened as in nearby residences.

Furthermore, Bachok et al. [15] backed this by specifying the ideal height and length of a road hump to be between 50 mm and 100 mm and 3 m–4 m, respectively, to attain a vehicle speed within 35 km/h in a residential area. Mohanty et al. [24] also demonstrated the influence of speed hump on the navigating speed of a vehicle. Their research incorporated twelve speed humps installed on major roads of Bhubaneswar city in India. They found that there was a reduction in speed starting 20 m before approaching the speed hump at 33 km/h, and 9.8 km/h at the speed hump.

Figure 3 summarizes the percentage reductions in vehicle speed associated with different speed hump types, vehicle types, and design characteristics, based on findings from previous studies [13,18,25].

While the research mentioned provides strong evidence about speed humps, much of it uses relatively small groups or single urban contexts. For example, Abdulmawjoud et al. [13] did not account for environmental or lighting conditions that may affect how a driver perceives speed humps. Similarly, Gamlath et al. [25] constrained their analyses by using only a limited set of fixed routes and types of vehicles. Future work should strive to use larger dataset variables and control for the behavioral variabilities across drivers and environmental regions. While geometry influences the immediate effect of a single-speed hump, the spacing between multiple humps is also a decisive factor in sustained speed control.

3.7.2. Quantitative Analysis of Design–Speed Interaction

A comparative synthesis of reviewed studies was performed to quantitatively analyze the relationship between the geometric parameters of speed humps and their effects on vehicle speed. The essence of hump height, design type, and observed speed reductions, as discussed in the selected studies, is summarized in

Table 4. Comparative table of hump geometry and its quantified impact on vehicle speed reduction across reviewed studies.

Source/Study	Hump Type	Height (mm)	Speed Reduction (km/h or %)	Notes
Gamlath et al. in 2023 [25]	Not specified	75	42.13%	Passenger car, noise + speed study
Skudai, Malaysia (Flat-top) [19]	Flat-top	90	52.00%	Malaysian residential road study
Abdulmawjoud et al. in 2021 [13]	Flat-top	100	71.60%	Mosul, Iraq
Abdulmawjoud et al. in 2021 [13]	Double hump	75	66.00%	Mosul, Iraq
Abdulmawjoud et al. in 2021 [13]	Single hump	100	60.00%	Mosul, Iraq
Obregón-Biosca in year 2020 [18]	General average	100	50.00%	Spain
SIRIM in 2009 [43]	Parabolic	75–100	↓ 12–15 km/h (85th percentile)	Based on a spacing of 90–180 m
Ministry of Works in year 2002 [31]	Flat/round/sinusoidal	50–100	30–60 km/h operating range	Design regulation (Malaysia); no % drop but linked to hump type

. Six reported values from field studies regarding the dimensions of the humps and their percentages of speed reduction were used to perform a Pearson correlation. Hump height appears to correlate positively and very strongly with percentage speed reduction (r = 0.89), confirming that higher speed humps are generally more effective in reducing vehicle speed. For example, a 100 mm flat-top hump in Mosul exhibited a speed reduction of 71.6% [13], while a 75mm circular profile in Malaysia reduced speed only by 46% [25]. The restricted number of field studies (n = 6) notwithstanding, a Pearson correlation coefficient of 0.89 between hump height and speed reduction indicates at least some initial quantitative evidence in favor of the geometric effect, suggesting that this correlation ought to be verified in future studies on larger datasets. Moreover, noise-related outputs also responded to the geometry of the humps; for example, Gamlath et al. in 2023 [25], showed that speed humps greater than 75 mm raised vehicle noise levels by approximately 0.7 dB, owing to increased suspension activity. These findings reinforce the need to consider the joints of grouped attributes of design on user experience. While indicative, the above-mentioned analysis also highlights consistent trends for the authors’ consideration of the joint design approach to maximize both speed control and the environmental impact.

3.8. Effects of Hump Spacing on Motor-Vehicle Speed

This section overviews the literature regarding how the appropriate spacing of speed hump can have an impact on the speed of a vehicle.

Empirical evidence from Malaysia highlights the importance of appropriate hump spacing for speed control. For instance, Sofi and Hamsa (2016) found that closely spaced road humps effectively reduced vehicle speeds, aligning with the recommended 35 km/h speed limit in residential zones [46]. Similarly, Pérez-Acebo et al. [39] empirically found an 80% correlation between the spacing between two successive traffic-calming measures and the speed gained in the median point between them. If traffic-calming measures are placed too close to one another, motorists do not have sufficient space to accelerate after navigating over the preceding one. Further, their study suggested an optimum of 200 m of space among traffic-calming measures; for an 85th percentile of speed below 50 km/h and a speed under 40 km/h, the recommended space between two successive traffic-calming measures is 75 m. Supporting this, García et al. in 2011 [51], conducted a microsimulation study that emphasized that a spacing of approximately 100 m between vertical traffic-calming devices effectively moderated speeds while maintaining reasonable traffic capacity. Their findings also highlighted that closer spacing, while increasing compliance, could lead to unnecessary delays, especially on higher-volume roads, reinforcing the need for balanced spacing based on context.

Contrasting these findings, Kveladze and Agerholm [52] advocate that the distance between two successive traffic-calming measures has impacted the moderate speed in the midpoint of speed-controlling devices, but their study did not provide any particular association between them. The conclusions derived declared spacing to be significant in predicting maximum speed selection. Similarly, Obregón-Biosca [18] advocated that the spacing between speed humps does not significantly affect vehicle speed when traversing these devices; however, it does influence pollutant emissions and additional fuel consumption. However, the study of Kiran et al. [53] revealed that speed reduction primarily relied on the spacing between the speed humps, and the maximum spacing of speed humps provided by the IRC is around 100–120 m. Speed-control measures also bring unintended consequences, including elevated traffic noise, which can affect urban quality of life.

Although these studies provide important characteristics of spacing and speed output, not much attention has been paid to the variability across regions of Malaysia in terms of application. The geometry and spacing of speed humps greatly affect traffic flow and safety; however, the actual field efficacy of either depends on the different conditions of the roads, local policies, and enforcement capability. For example, in year 2023, Aboud et al. [54] in Johor found that medium-severity humps (SB2) reduced speeds from 66.6 km/h to 39.4 km/h, while high-severity humps (SB3) dropped speeds dramatically to 5.34 km/h, also impacting traffic flow rates. Meanwhile, Shwaly et al. (2024) [17] show that denser spacing (1.33 humps/km) increased motorcycle fuel consumption by an additional 13.73%.

Comparative city-level findings corroborated this pattern: Kuala Lumpur and Selangor showed that better adherence to design guidelines is an effective way of achieving speed control (Ahmad et al., 2024) [55], while studies in Johor Bahru and Sarawak have revealed notable inconsistences like the spacing of humps, irregularities in signage, or excessive heights of humps due to little technical supervision or community installation (Tan et al., 2021; Abd Rahim, 2023) [5,56]. Local variances related to this emphasize the need for localized traffic-calming approaches. One size does not fit all in terms of design standards. Site-sensitive approaches should be instituted in order for speed humps to be rendered effective and safe for the whole of Malaysia, given its heterogeneity in urbanity or rural setting. Design standards alone would not guarantee success.

In Malaysia, the spacing of speed humps is between 90 and 180 m as per the Highway Planning Unit and SIRIM guidelines. All these were examined to keep the vehicle speeds above 40 km/h and below acceptable limits while minimizing the excessive braking and acceleration. However, these spacing norms are often based on general recommendations rather than empirical testing across varied road types and traffic conditions. Zainuddin et al. (2014) [14] noted that many installations do not adhere to spacing recommendations, which can undermine effectiveness and consistency. Similarly, Abdulmawjoud et al. (2021) and Mashrosa et al. (2020) highlight the need for context-aware spacing strategies in university and arterial road settings, respectively [13,19]. There remains limited research testing alternative spacing layouts within the Malaysian context to assess their comparative impact on speed moderation, fuel consumption, and driver behavior. Future studies could explore experimental deployments of varying spacing intervals (e.g., 75 m, 100 m, 150 m) in both residential and arterial roads to refine national design standards.

3.9. Effects of Road Humps on Traffic Noise

3.9.1. Impact of Road Humps on Noise Levels

Traffic noise has been a major concern for human well-being and environmental pollution. Excessive noise levels can cause sleep disturbances, health problems, and irritation. A Malaysian study showed that the noise levels exceeded the permissible limits during the day- and nighttime in residential areas [57]. Furthermore, the installation of road humps can lead to increased traffic noise, as it is linked to the change in speed and volume near the humps. Traffic noise is increased when vehicles slow down or speed up near humps. A study by Sofi and Hamsa [46] was conducted in residential areas, which revealed that the road humps had little effect on the vehicles passing over them. The highest noise level was recorded at Jalan Keramat at 72.36 dB, and the lowest was recorded at Jalan Setiawangsa 21 at 57.88 dB.

3.9.2. Design Parameters and Noise Outcomes

According to Gamlath et al. [25], the increase in the hump height led to a reduced speed, but eventually, it increased noise levels to 0.7 dB and exceeded the limits set by the environmental authority. Furthermore, even minor changes in hump height were found to significantly delay drivers and elevate noise levels near the hump. Likewise, a study was conducted in Qatar by Haroon et al. [27], which analyzed the relationship between traffic flow and noise levels, resulting in a positive correlation. The statistical tests concluded that the noise level was higher at speed humps. Speed humps on 4-lane roads created more noise than 2-lane roads due to wider gaps which promote faster driving. The findings of the study by Fabra-Rodriguez et al. [58] were based on a numerical model that combined two methods to evaluate the noise caused by vehicles passing over the humps. In addition to technical evaluations, understanding the public perception of road humps is vital to assess the acceptability and overall success of these interventions.

3.10. Public Perceptions

In residential areas, the placement of road humps has an impact, so the consideration of the resident is important regarding the presence of road humps in their locality. One such study revealed that the resident perception of road humps closely corresponds with the field measurements of the survey, thereby highlighting the inability of the road humps to reduce noise, which can result in public dissatisfaction [26].

In general, many studies have evaluated the noise levels at different hump locations with the help of field surveys, models, data collections, and simulations. On the contrary, a survey of more than 50% was conducted in Japan, whose results showed that the resident believed the neighborhood became more livable due to the installation of speed humps [59]. Given the empirical evidence and public feedback, it is important to examine existing design standards and offer recommendations for better implementation.

3.11. Design Standards and Policy Recommendations

The findings from multiple studies demonstrate the effectiveness of traffic-calming approaches, specifically speed humps in residential areas. Moreover, it was observed in a study conducted in Malaysia that most of the road humps placed did not meet the standard designs. Further, properly designed road humps, particularly the flat-top ones, were efficient in reducing vehicle speed by 52% and round tops by 46% [60]. This indicates the significance of road humps in the reduction in vehicle speed. The hump design should follow the standard profiles with clear signage and markings. Also, another study highlighted the need for pavement structures around speed humps to reduce vehicle speed and promote smaller gaps than the wider ones between the humps for effective results [61]. The concrete paving around the devices can wear out with time, so specific curb inlets can be used instead of standard ones to lessen the damage. A recent study found that speed-control surfaces can be applied to traditional bumps for slowing down two-wheelers, as they create less discomfort for drivers [61]. The usage of speed humps significantly contributed to noise levels, thereby making them least effective in industrial and residential zones. Studies such as that by Marusceac et al. [62] suggested the use of asphalt speed breakers, as they create less noise and are effective when used in long configurations. The study also sheds light on the noise levels at higher frequencies, which tend to be of a similar pattern.

Few studies are present on the application of traditional models to low-income countries, adopted from high-income countries, so their ability to work effectively in mixed traffic is not clear, thereby indicating the need for future studies to incorporate the complexity of speed and crash association in mixed traffic [63]. Various studies have highlighted the use of other traffic measures, including chicanes, by taking the concerns of the citizens into policymaking to create roads that cater to all users [44]. Additionally, future studies should highlight the impact of these measures on roads with bus and emergency vehicle routes, as it leads to more delays, thereby emphasizing its downside [20]. Limited research has been conducted on the usage of combining multiple traffic-calming measures for a combinatorial effect. To improve the efficacy of traffic calming, future recommendations also include exploring the use of land management for improving safety and environmental quality by reducing noise pollution [64].

Current guidance and research provide technical details that enhance the design and implementation of speed humps as a traffic-calming method. For instance, the National Association of City Transportation Officials (NACTO) indicates that speed humps should be made with a height of 3–4 inches at a width of 12–14 inches, with ramp lengths of 3–6 feet depending on the speed reduction desired. The ramp should have a slope no greater than 1:10 or flatter than 1:25, and the side slopes on the tapers should not be greater than 1:6 for safe and consistent vehicle deceleration [58]. NACTO also states that humps should not be spaced any farther than 500 feet apart to provide effective speed moderation; closer spacing allows for more significant speed reductions [65]. In addition, this is supported by rapid scientific evidence from Pérez-Acebo et al. (2020) [39], which discussed optimal spacing ranges of 75 and 200 m; if the spacing is longer than this, the speed between humps is increased, and ultimately, the speed hump intervention is limited. The Toolkit also recommends the use of asphalt materials in residential and industrial zones to minimize noise pollution and improve community acceptance [66]. To translate these technical standards into practice, implementation measures must be taken to improve the effectiveness of speed humps in practice. Measures include involving local traffic authorities and communities in the planning phase, developing standardized pre-approved templates for humps, ensuring that all warning signs are placed consistently (e.g., at 50 m and 20 m before the humps), and evaluating the hump installation through actual speed reductions and resident feedback. For instance, in Taman Setiawangsa in Kuala Lumpur, Sofi and Hamsa (2016) [46] indicated that well-spaced and marked humps reduced vehicle traveling speeds from approximately 30 km/h to under 10 km/h at hump locations, and that drivers displayed smoother deceleration characteristics. In a similar vein, Yaacob and Hamsa (2013) [45] reported that following the geometrics of the humps resulted in driver behavior that was uniform and accepted throughout the community in Taman Setapak. Conversely, investigations in Sarawak and Johor Bahru have examined velocity issues related to community-installed measures (despite engineering oversight at a distance) that were either over the maximum height or that had inconsistent spacing, which resulted in complaints about discomfort and safety [5]. These collectively considered guidelines provide a comprehensive framework for enhancing the placement of speed humps and the associated safety benefits in a range of traffic environments. This integrated set of recommendations provides a strong basis for improving speed hump deployment and safety outcomes in a variety of traffic situations.

To make things even more practical, instructions are required for the implementation. First, local governments can develop a standardized contact approval template for hump geometry and materials based on national (e.g., SIRIM) or international (e.g., NACTO) consistency. For example, we used a pre-approved flat-top profile with a height of 75–100 mm and a length of 3.7–4.25 m, and placed reflective signage at 50 m and 20 m before each installation on the roadway; the final speed humps for similar hump geometry and conditions dropped to under 10 mph and demonstrated consistently smooth deceleration patterns in Taman Setiawangsa (K.L.) [46]. We later improved community satisfaction and driver conformity in Taman Setapak through dependable adherence to dimensions [46]; delineating a clear role and clear usage scenarios with expected specification assurance should result in high acceptance.

Alternatively, in Sarawak and Johor Bahru we have demonstrated that either non-compliant over-height humps or unregulated community installation would lead to discomfort/unpleasantness and many safety complaints [5]. Thus, this also illustrates the importance of the four operational steps summarized from international guidelines (e.g., NACTO, WHO) and incorporated from case studies and exemplar speed hump literature in Malaysia and the global urban traffic-calming literature [1,56].

• Pre-installation phase: road safety audits, stakeholder engagement, and road classification.
• Design and construction: modular pilots, ramp slope limits, and asphalt material choice.
• Monitoring and evaluation: real-time speed sensors and community feedback.
• Governance and enforcement: local authority training and registry of compliant installations.

3.12. Practical and Theoretical Implications

The empirical evidence presented in this study underscores the critical role of speed humps as an effective traffic-calming measure to reduce vehicle speeds and, consequently, lower accident severity and frequency in urban and residential areas. Practically, this supports policymakers and traffic engineers in prioritizing the installation and optimal design of speed humps, particularly trapezoidal and flat-topped types, to achieve substantial speed reductions, often between 34% and 75%. The findings also highlight the importance of appropriate spacing (ideally around 75 to 200 m) to maintain consistent speed control without compromising road capacity or increasing driver frustration.

From a theoretical perspective, the study advances our understanding of how geometric characteristics such as hump height, shape, and length interact with vehicle types to influence both speed and environmental noise impacts. The demonstrated link between increased hump height and noise elevation, especially in passenger cars, indicates a trade-off that requires careful balancing between safety benefits and community noise concerns. Moreover, the context-sensitive nature of traffic-calming effectiveness, supported by mixed findings across regions, suggests that future theoretical models should integrate environmental, behavioral, and infrastructural variables to predict outcomes more accurately.

Additionally, from the studies reviewed and the synthesis, some general design patterns can be established. Speed humps between 75 and 100 mm in height, 3.7–4.25 m in length, and spaced 75–120 m apart consistently have reduced speeds without sacrificing driver comfort. In addition, shape matters; flat-top or trapezoidal humps were consistently associated with the best traffic-calming outcomes, which supports the need for clear/drawn categories in design attributes (e.g., short, medium, and long for spacing). Accordingly, this study recommends updating Malaysian design manuals to include a typology-based classification system and integrated design standards that optimize spacing, shape, and geometry to maximize both safety and public satisfaction.

The insights regarding public perceptions further highlight the complexities involved in the implementation of traffic-calming strategies; specifically, the importance of engaging communities to address critical issues of noise or inconveniences associated with the interventions. Combined, the practical and theoretical imperatives provide a comprehensive framework for devising and evaluating speed hump designs and implementation strategies that incorporates safety, environmental sustainability, and social acceptance. The synthesis also indicates that combined multi-modal approaches to traffic calming combining speed humps, chicanes, and land-use planning create positive results for safety and environmental quality as well. In this regard, integrating citizen feedback into the design and implementation process can ensure that traffic-calming devices serve all users effectively.

4. Study Limitations

While past research has provided meaningful, though occasionally conflicting, understandings of the effects of speed hump spacing on vehicle speed, there are still many gaps. For example, Malaysian guidelines are explicit regarding the measurements and spacing for speed humps, but they do not categorize these parameters into relatively defined categories (for instance, short, medium, and long intervals). The processes by which many geometric features (for example, height, length, and shape) involve spacing to influence speed reduction are not clearly outlined, nor are the relationships explored empirically. Also, the enforcement of standards in the normal course of a Malaysian roadway is inconsistent, and empirical research typically lacks full data relating to roadway conditions, flows, and conformity to design specifications. The variability typically may not support generalizability and replicability. The targeted and systematic classification of speed hump spacing, and how geometric design parameters relate to spacing in informing potential traffic-calming design, should be the focus of future research. Our study helps in taking a step towards the latter by examining data about how spacing patterns and design features influence vehicle speed reduction, particularly with regard to local implications. Moreover, this review has not considered the interaction of speed humps with bicycles and micromobility devices (i.e., e-scooters), which are becoming increasingly prevalent in urban design. The current design and placement of vertical traffic-calming devices may also raise safety or comfort concerns for those users based on stability concerns or increased vibration. As the world continues to shift toward active and sustainable transport modes, subsequent studies should test how geometry, material, and the spacing of humps impact micromobility and non-motorized users. Including this facet would make traffic-calming measures more inclusive and supportive of all road users.

5. Conclusions

This study provides a comprehensive review of speed humps as a vertical traffic-calming device, with an emphasis on their use in Malaysia and other international contexts. Consistently, researchers have found that speed humps are effective at both lowering vehicle speed and improving road safety; studies document reductions in speed from around 15–50%, depending on the geometry (height, width, ramp length) and spacing of speed humps, and several factors in the road context.

However, the effectiveness of speed humps does not apply to every traffic environment. Effectiveness is not uniform across all contexts; speed humps’ effectiveness is related to traffic volume, a mix of vehicles (i.e., passenger vehicles compared to heavy trucks), and the kind of road it is (e.g., a residential street compared to an arterial road). For instance, speed humps effective in low-volume residential areas may trigger excessive braking, noise, or discomfort when applying the same speed humps to high-volume freight routes. Similarly, strategies regarding the spacing and dimensions of humps must be relevant to road function and posted speed limits. The knowledge from the review illustrates that context-sensitive design and implementation should take place.

Moreover, while the review supports the safety advantages of speed humps, it does reveal some significant limitations to their real-world implementation. In Malaysia, many design standards have not been strictly adhered to, and the enforcement of these design standards has been inconsistent, which has led to different performance outcomes, and sometimes dissatisfaction. Trade-offs exist, such as the increase in fuel consumption, vehicular emissions, and noise, especially, when either the speed hump location or the dimensions are not optimal for the surrounding built environment. Thus, these findings should be used to treat the existing roadway conditions, enforcement capacity, and community characteristics. Future research should conduct some quantitative correlation analyses with larger datasets to identify the optimal hump configurations under alternative traffic and environmental conditions. Also, the design guides should discuss alternative adjustments based on the vehicle classification structure and peak-hour traffic volume in relation to efficiency and comfort.