Outcomes of Speed Management Strategies on Road Traffic Crashes: A Systematic Review

1. Introduction to Speed Management and Road Safety

The challenge of road safety is a complex issue with a global impact, and effective speed management is a cornerstone in mitigating the risks associated with road traffic crashes. Speeding not only increases the likelihood of a crash but also significantly contributes to the severity of the resulting injuries and fatalities [1]. The kinetic energy involved in a collision rises exponentially with speed, meaning that even small increases in speed can lead to disproportionately more severe outcomes. Therefore, the implementation of comprehensive and effective speed management strategies is essential for creating safer road environments and reducing the unacceptable toll of road traffic deaths and injuries [2]. These strategies aim to address the multifaceted nature of speeding, encompassing measures that influence driver behavior, roadway design, and vehicle technology, all with the overarching goal of mitigating the negative impacts of speeding on road safety [1].

Speeding has emerged as a primary concern on a global scale, largely due to its far-reaching and detrimental impacts on both road crashes and environmental pollution [1]. The correlation between excessive speed and the incidence and severity of road accidents is well-documented, with numerous studies highlighting how higher speeds reduce a driver's reaction time, increase stopping distances, and amplify the force of impact in the event of a collision. Beyond the immediate consequences of road accidents, speeding also contributes significantly to environmental degradation through increased fuel consumption and the resultant emissions of greenhouse gases and other pollutants. This dual impact on safety and the environment underscores the urgent need for effective speed management strategies that can address both of these critical concerns. In regions such as the Eastern Mediterranean, high road trauma levels persist, further emphasizing the critical need for robust speed management interventions [3]. These regions often face unique challenges, including rapid urbanization, inadequate infrastructure, and varying levels of enforcement, which exacerbate the problem of speeding and its associated consequences. To combat the pervasive problem of speeding, many countries around the world are implementing a range of speed enforcement policies and initiatives [4]. These policies often include a combination of measures, such as setting and enforcing speed limits, deploying speed cameras, implementing traffic calming measures, and utilizing public awareness campaigns to promote safer driving behaviors.

This systematic review is designed to provide a comprehensive overview of the current state-of-the-art speed management measures and to critically assess their impacts on various speed-related outcomes [1]. By examining a wide range of studies and interventions, this review seeks to synthesize the available scientific evidence and provide insights into the effectiveness of different approaches to speed management. A key objective of this review is to synthesize the available evidence regarding the effectiveness of various speed management strategies in reducing road traffic crashes [5]. This involves a detailed analysis of studies that have evaluated the impact of different interventions, such as speed cameras, variable speed limits, and traffic calming measures, on crash rates and severity. By bringing together the findings from diverse studies, the review aims to provide a more comprehensive and nuanced understanding of what works, what doesn't, and under what circumstances. The scope of this review encompasses a wide array of speed management strategies and their outcomes on road safety [1]. This includes not only traditional measures like speed limits and enforcement but also more advanced technologies and approaches, such as intelligent speed adaptation (ISA) systems, sectional speed enforcement systems (SSES), and innovative traffic calming devices. By examining the full spectrum of available strategies, the review aims to offer a holistic perspective on speed management and its potential to improve road safety.

2. Defining Speeding and Its Impact on Crash Outcomes

Speeding is a critical factor in road traffic incidents and is commonly defined as traveling at speeds exceeding the posted or legally mandated speed limit [6]. This definition serves as the foundation for both enforcement efforts and public awareness campaigns aimed at curbing excessive speeds on roadways. However, the concept of speeding extends beyond simply exceeding a numerical limit; it also encompasses driving at speeds that are inappropriate for the prevailing conditions, such as adverse weather, heavy traffic, or reduced visibility. In these situations, even driving within the posted speed limit can be considered speeding if it compromises safety. Over-speeding is a pivotal factor in fatal traffic crashes globally, underscoring the critical need for robust speed management strategies to mitigate this risk [2]. The consequences of over-speeding are far-reaching, contributing not only to the initial crash event but also to the severity of injuries sustained by those involved. Therefore, effective speed management is essential for reducing both the incidence and the impact of road traffic crashes. Speeding is a key factor contributing to road traffic crashes, making studies on speed reduction devices particularly relevant in the context of poor road safety outcomes worldwide [7]. The recognition of speeding as a primary cause of accidents has spurred significant research efforts focused on developing and evaluating various speed reduction technologies and interventions. These studies aim to identify the most effective strategies for influencing driver behavior and creating safer road environments.

The correlation between speeding and the severity of crashes is well-established, with a positive and exponential relationship existing between vehicle speed and crash risk severity [4]. This relationship implies that as vehicle speed increases, the likelihood and potential consequences of a crash escalate disproportionately. Higher speeds reduce the amount of time drivers have to react to unexpected events, increase stopping distances, and amplify the force of impact in the event of a collision. These factors collectively contribute to more severe injuries and a greater risk of fatalities. Higher speeds are associated with more severe pedestrian injuries and an increased risk of death [8]. Pedestrians are particularly vulnerable in collisions with vehicles, and even small increases in vehicle speed can significantly elevate the risk of serious injury or fatality. The heightened risk to pedestrians underscores the importance of implementing speed management measures in areas with high pedestrian traffic, such as urban centers and residential neighborhoods. Increased speed limits have been shown to result in more injuries and fatal crashes, providing empirical evidence of the direct link between speed and crash outcomes [9]. Studies that have examined the effects of raising speed limits have consistently found that these changes lead to a greater number of accidents and more severe injuries, highlighting the potential dangers of policies that prioritize speed over safety.

Statistical evidence provides compelling support for the link between speed and fatalities and injuries, with significant data highlighting the devastating consequences of speeding on roadways. In 2021, over 12,000 speed-related fatalities were reported in the United States alone, representing a substantial portion of all traffic deaths [2]. This staggering figure underscores the urgent need for effective speed management strategies to reduce the unacceptable toll of lives lost due to speeding. Speeding is a major contributor to serious crashes, with management interventions demonstrated to reduce speeds and trauma, underscoring the effectiveness of targeted interventions in mitigating the harmful effects of excessive speed [6]. These interventions, such as speed cameras and traffic calming measures, have been shown to not only lower average speeds but also to decrease the incidence and severity of crashes. Road traffic injuries are projected to become a leading cause of mortality worldwide, further emphasizing the critical importance of addressing speeding as a key risk factor [10]. The global burden of road traffic injuries is disproportionately high in low- and middle-income countries, where resources for road safety interventions are often limited. Therefore, effective and affordable speed management strategies are essential for reducing the number of deaths and injuries on roadways around the world.

3. Conventional Speed Management Measures

Conventional speed management measures encompass a range of traditional strategies designed to control vehicle speeds and improve road safety. These measures typically include setting speed limits, implementing traffic calming measures, and conducting police enforcement [1]. Speed limits establish the maximum legal speed for a given roadway, while traffic calming measures physically alter the road environment to encourage slower speeds. Police enforcement involves the use of officers and technology to detect and penalize speeding drivers. Traffic calming measures are systematically planned to reduce driving speeds, particularly in urban areas and residential neighborhoods [11]. These measures aim to create safer, more livable environments by reducing the speed and volume of traffic. Common traffic calming techniques include speed humps, speed tables, chicanes, and road narrowing. Speed limit enforcement is a common method used to control vehicle speeds, with police officers and automated systems like speed cameras employed to detect and penalize speeding drivers [12]. Effective enforcement requires a combination of visible patrols, consistent application of penalties, and public awareness campaigns to deter speeding.

Conventional measures are often effective in reducing vehicle speed in the vicinity of interventions, providing localized improvements in road safety [1]. For example, speed humps can significantly lower speeds on residential streets, while increased police presence can deter speeding on highways. However, the impact of conventional measures is often limited in space, leading to the problem of event migration, where drivers simply slow down in the immediate area of the intervention and then resume speeding afterward [1]. This phenomenon reduces the overall effectiveness of these measures and highlights the need for more comprehensive and sustained approaches to speed management. Speed control measures are useful in calming vehicular speeds, but poor design can endanger users, indicating the importance of careful planning and implementation [10]. For example, poorly designed speed humps can cause drivers to brake suddenly or swerve, increasing the risk of accidents. Similarly, inadequate signage or lighting can make traffic calming measures difficult to see, negating their intended effect.

Conventional speed management measures are predominantly implemented due to lower initial costs, making them an attractive option for many jurisdictions with limited budgets [1]. Compared to more advanced technologies like variable speed limits and intelligent speed adaptation systems, traditional measures are generally less expensive to install and maintain. However, implementing red light camera programs requires considering costs, benefits, and potential increases in certain crash types, highlighting the need for a thorough cost-benefit analysis before deploying these technologies [5]. While red light cameras can be effective in reducing certain types of crashes, such as angle collisions, they may also lead to an increase in rear-end collisions as drivers brake suddenly to avoid a ticket. Lower speed limits may prevent fatalities and serious injuries, with benefits outweighing costs, suggesting that these measures can be economically justified based on their safety benefits [13]. Studies have shown that reducing speed limits can lead to a significant decrease in the number of crashes and the severity of injuries, resulting in substantial cost savings due to reduced healthcare expenses and property damage.

4. Advanced Speed Management Technologies

Advanced speed management technologies represent a significant evolution in strategies aimed at controlling vehicle speeds and enhancing road safety. These technologies often leverage real-time data, advanced sensors, and intelligent algorithms to dynamically adjust speed limits and provide drivers with timely feedback. Promising approaches in this area include variable speed limits (VSLs) and intelligent speed adaptation (ISA) systems, which offer more flexible and responsive solutions compared to traditional fixed speed limits [1]. Variable speed limit (VSL) is a useful management tool for alleviating traffic congestion and enhancing safety, adjusting speed limits based on real-time traffic conditions, weather, and other factors [14]. VSLs can help to smooth traffic flow, reduce the risk of collisions, and improve overall roadway efficiency. Intelligent speed adaptation (ISA) systems are promising for solving the limitations of conventional measures, providing drivers with real-time feedback and warnings to help them maintain safe speeds [1]. ISA systems can be either advisory, providing visual or audible alerts, or mandatory, actively limiting the vehicle's speed.

Sectional speed enforcement systems (SSES) represent a significant advancement in speed enforcement technology, addressing some of the limitations of traditional point-based speed cameras. Sectional speed enforcement systems (SSES) enforce overspeeding based on average travel speed over a section, rather than at a specific point, which encourages drivers to maintain consistent speeds over longer distances [15]. This approach can help to reduce the "kangaroo jump" effect, where drivers slow down only in the immediate vicinity of a speed camera and then speed up again afterward. Evaluation of SSES showed reduced crash occurrence after installation, indicating the potential safety benefits of this technology [15]. By monitoring average speeds over a section of roadway, SSES can deter speeding and promote safer driving behaviors. SSES addresses the issue of drivers adjusting speeds only in the vicinity of enforcement locations, promoting more consistent and safer speeds over longer stretches of road [15]. This makes SSES a more effective tool for managing speed and reducing the risk of collisions.

Intelligent traffic calming devices represent a new frontier in efforts to manage vehicle speeds and enhance safety, particularly in urban and residential areas. Intelligent traffic calming devices are promising approaches to solving the limitations of conventional measures, using sensors and adaptive technologies to respond to real-time traffic conditions and pedestrian activity [1]. These devices can adjust their level of intervention based on factors such as vehicle speed, traffic volume, and the presence of pedestrians, providing a more flexible and responsive approach to traffic calming. Traffic calming measures include speed tables, chicanes, and road narrowing, all designed to physically alter the road environment and encourage slower speeds [11]. These measures can be particularly effective in reducing speeds in residential areas and near schools, where pedestrian and cyclist activity is high. Speed tables guarantee the greatest conditioning on speed, reducing average speed significantly and providing a physical deterrent to speeding [11]. Speed tables are raised sections of roadway that force drivers to slow down, making them an effective tool for reducing speeds and improving safety.

5. The Role of Speed Cameras in Reducing Crashes

Speed cameras have become a widely implemented tool in the effort to reduce speeding and improve road safety, with numerous studies examining their effectiveness in various settings. Speed cameras can be an effective tool in reducing speeds and subsequent traffic crashes, providing a means of automated enforcement that can deter speeding and improve driver behavior [4]. By capturing images of speeding vehicles, speed cameras allow law enforcement to issue tickets and penalize drivers who violate speed limits. Speed cameras are shown to reduce speeds and trauma, but evaluations report a range of outcomes, highlighting the complexity of assessing their impact [6]. While many studies have found that speed cameras are effective in reducing crashes and injuries, others have reported mixed results, with some studies showing only a small or negligible effect. Implementation of ASE cameras significantly reduced road traffic deaths, serious injury crashes, and fatal crashes, demonstrating the potential of this technology to save lives and prevent injuries [16]. A study in Rwanda found that the implementation of automated speed enforcement (ASE) cameras was associated with a significant reduction in road traffic deaths and serious injuries, suggesting that this technology can be particularly effective in low-income countries.

Speed cameras have a multifaceted impact on driver behavior, influencing not only average speeds but also patterns of acceleration and deceleration. Speed cameras lead to punctual speed reduction, known as the kangaroo jump effect, where drivers slow down abruptly as they approach a camera and then speed up again afterward [7]. This behavior can be problematic, as it can lead to sudden braking and acceleration, increasing the risk of rear-end collisions. Speed cameras have varying impacts depending on topographic profile, time of day, and weather conditions, highlighting the importance of considering these factors when evaluating their effectiveness [7]. For example, speed cameras may be more effective on flat roads than on hilly roads, and their impact may vary depending on whether it is day or night. Drivers adjust vehicle speeds in the vicinity of speed camera locations, demonstrating an awareness of the enforcement and a desire to avoid receiving a ticket [15]. This suggests that speed cameras can be an effective deterrent, but it also highlights the need for strategies to encourage drivers to maintain safe speeds even when they are not near a camera.

Various factors can influence the outcomes of speed camera evaluations, making it challenging to draw definitive conclusions about their effectiveness. Factors contributing to findings include genuine differences delivered by camera programs and variations in evaluation methodology, highlighting the need for careful study design and data analysis [6]. Differences in camera placement, enforcement policies, and public awareness campaigns can all affect the impact of speed cameras. Ensuring full chain requirements for general deterrence are met is crucial for maximizing safety with speed cameras, including clear signage, consistent enforcement, and public communication [6]. Without these elements, speed cameras may not be as effective in deterring speeding and reducing crashes. Unpredictability of enforcement versus signposted cameras improves the effectiveness of speed cameras, as drivers are more likely to comply with speed limits if they believe they could be caught speeding at any time [6]. This suggests that a combination of visible and hidden speed cameras may be the most effective approach to speed enforcement.

6. Infrastructure Design and Speed Management

Roadway characteristics play a critical role in influencing driver behavior and the likelihood of over-speeding. How roadway characteristics and built environment influence the extent of over-speeding is a key consideration in road safety management [2]. By understanding how different road features affect driver speeds, engineers and policymakers can design safer roadways and implement more effective speed management strategies. The number of lanes, dwelling unit types, and proximity to schools affect over-speeding tendencies, highlighting the complex interplay between roadway design and the surrounding environment [2]. For example, wider roads with more lanes may encourage higher speeds, while the presence of schools may prompt drivers to slow down. Aggregation tends to underestimate the influence of roadway factors on over-speeding, suggesting that more detailed analysis is needed to fully understand these relationships [2]. Studies that aggregate data across different types of roads may fail to capture the specific effects of individual road features on driver behavior.

The built environment surrounding a roadway can have a significant impact on driver behavior and the prevalence of speeding. Built variables presented mixed results, with one-unit dwellings associated with increased over-speeding, suggesting that residential density may influence driver speeds [2]. Areas with lower residential density may encourage higher speeds due to the perception of lower risk. Proximity to schools is associated with a decrease in over-speeding, indicating that drivers tend to slow down in areas where children are present [2]. This highlights the importance of implementing speed management measures in school zones to protect young pedestrians. Specific built environment features, such as crosswalk design and sidewalk width, are linked to older pedestrian crashes, underscoring the need for age-friendly infrastructure design [17]. These features can affect the safety and accessibility of roadways for older adults, who are particularly vulnerable to traffic injuries.

Geometric design is a fundamental tool for managing vehicle speeds and enhancing road safety. Impact is typically limited through vehicle speed management (e.g., limits, enforcement, geometric design), emphasizing the importance of integrating design considerations into speed management strategies [18]. By carefully designing roadways, engineers can encourage drivers to maintain safe speeds and reduce the risk of collisions. Road geometry and speed significantly affect traffic accidents, highlighting the need to consider these factors in road design and safety management [19]. Sharp curves, steep grades, and narrow lanes can all contribute to crashes if drivers are traveling at excessive speeds. Straight and one-lane road geometric formations observe a large number of crashes, suggesting that these types of roadways may be particularly prone to accidents [19]. This may be due to factors such as driver fatigue, inattention, or a false sense of security.

7. The Safe System Approach and Speed Management

The Safe System approach, also known as Vision Zero, represents a paradigm shift in road safety management, prioritizing the elimination of death and serious injury as an outcome of road travel. The Safe System vision aspires to minimize death and serious injury as an outcome of road travel, recognizing that humans are fallible and that crashes are inevitable [18]. The goal is to design a road system that minimizes the severity of crashes when they do occur, protecting all road users from serious harm. Control of vehicle speed is a central tenet of the safe systems approach to road safety, recognizing that speed is a key determinant of crash severity [9]. By managing speeds, road authorities can reduce the risk of serious injuries and fatalities. The Safe System Approach considers speed management as a pivotal factor in achieving a safer traffic system, emphasizing the need for a holistic and integrated approach [3]. This approach involves not only setting and enforcing speed limits but also designing roadways and vehicles that minimize the risk of crashes and protect occupants in the event of a collision.

A core principle of the Safe System approach is to focus on impact elimination and kinetic energy management. Engineering focuses on impact elimination and limiting kinetic energy in case of impact, recognizing that these are the primary determinants of crash severity [18]. By reducing the force of impact, the risk of serious injuries can be significantly reduced. Impact is typically limited through vehicle speed management, enforcement, and geometric design, highlighting the importance of these strategies in creating a safer road system [18]. By managing speeds, designing safer roadways, and enforcing traffic laws, road authorities can reduce the risk of crashes and minimize the severity of injuries. Right-angle head-on crashes at approximately 30 km/h are likely to produce MAIS3+ injuries, a threshold considered critical in discussions of road safety [18]. This underscores the importance of managing speeds in urban areas and at intersections to protect vulnerable road users.

Several countries have successfully adopted the Safe System approach, achieving significant reductions in road traffic fatalities. Sweden, the U.K., and the Netherlands implement effective road safety measures, serving as models for other countries seeking to improve their safety performance [20]. These countries have implemented a range of strategies, including strict enforcement of traffic laws, investment in safer infrastructure, and promotion of safer vehicles. Recommendations for improving road safety in the U.S. include lowering BAC limits and improving speed limit enforcement, suggesting that these measures could help to bring the U.S. closer to the safety performance of leading countries [20]. By adopting a Safe System approach and implementing evidence-based strategies, the U.S. could significantly reduce the number of deaths and injuries on its roadways. British Columbia, Canada, saw increases in insurance claims and fatal crashes after raising speed limits, providing a cautionary tale about the potential consequences of prioritizing speed over safety [9]. This highlights the importance of carefully considering the potential impacts of any changes to speed limits and other road safety policies.

8. Speed Management in Low and Middle-Income Countries (LMICs)

Low and Middle-Income Countries (LMICs) face unique challenges in addressing road safety, with a disproportionately high burden of road traffic injuries and fatalities. Over 90% of global road injury burden is borne by Low and Middle-Income countries (LMICs), highlighting the urgent need for effective interventions in these regions [10]. Factors such as rapid urbanization, inadequate infrastructure, and limited resources contribute to the high rates of road traffic crashes in LMICs. Rwanda is the first low-income country to implement a national Automated Speed Enforcement (ASE) policy, demonstrating a commitment to improving road safety through innovative approaches [16]. This initiative could serve as a model for other LMICs seeking to implement effective speed management strategies. LMICs face unique challenges in implementing effective road safety interventions, including limited resources, weak enforcement, and a lack of public awareness [21]. Overcoming these challenges requires a multi-faceted approach that addresses both the technical and social aspects of road safety.

Effective interventions for unintentional injuries in LMICs often focus on addressing key risk factors such as speeding and drink-driving. Most successful interventions for preventing deaths in LMICs include speed enforcement and drink-driving measures, highlighting the importance of targeting these behaviors [22]. By implementing effective enforcement and public awareness campaigns, LMICs can significantly reduce the number of deaths and injuries on their roadways. Legislation and enforcement have the largest impact on road safety in LMICs, suggesting that these measures are particularly effective in these settings [21]. Strict enforcement of traffic laws, combined with clear and effective legislation, can help to deter risky driving behaviors and improve road safety. Combined multi-faceted strategies are most effective in Sub-Saharan Africa, indicating the need for a holistic approach that addresses multiple risk factors [10]. This approach may include measures such as improving road infrastructure, promoting safer vehicles, and educating the public about road safety.

Several LMICs have implemented successful speed management initiatives, demonstrating the potential for these strategies to improve road safety in resource-constrained settings. Implementation of ASE cameras in Rwanda significantly reduced road traffic deaths, serious injury crashes, and fatal crashes, providing evidence of the effectiveness of this technology in an LMIC context [16]. This success story highlights the potential for LMICs to adopt innovative approaches to speed management and achieve significant improvements in road safety. A study in two Chinese cities showed that vehicles above the speed limit decreased after targeted interventions, demonstrating the potential for public awareness campaigns and enforcement to change driver behavior [23]. By raising awareness of the risks of speeding and implementing effective enforcement measures, LMICs can encourage drivers to adopt safer driving habits. In Yaound, Cameroon, implementing evidence-based strategies could potentially reduce fatalities and serious injuries, highlighting the potential for LMICs to achieve significant improvements in road safety through targeted interventions [24]. This underscores the importance of conducting research to identify the most effective strategies for addressing road safety in specific LMIC contexts.

9. The Role of Technology and Innovation in Speed Management

Technology and innovation are playing an increasingly important role in speed management, offering new tools and strategies for reducing crashes and improving road safety. Unmanned Aerial Vehicles (drones) have emerged as promising tools in traffic monitoring and accident prevention, providing a cost-effective and flexible means of gathering data and enforcing traffic laws [25]. UAVs can track vehicles, estimate speeds, and detect traffic rule violations in real-time, providing law enforcement with valuable information for targeting enforcement efforts [25]. By monitoring traffic conditions and identifying speeding vehicles, drones can help to deter risky driving behaviors and improve road safety. Drones offer wide coverage, cost-effectiveness, and flexibility for traffic monitoring, making them an attractive option for many jurisdictions [25]. Compared to traditional methods of traffic monitoring, such as stationary cameras and police patrols, drones can cover a larger area and be deployed more quickly and easily.

Machine learning is also being applied to the problem of speed management, with researchers developing algorithms to predict crash risk and identify factors that contribute to speeding. Machine learning methods can identify causes of traffic crashes associated with driver behavior, providing insights into the factors that contribute to risky driving behaviors [26]. By analyzing data on driver behavior, road conditions, and other factors, machine learning algorithms can identify patterns and predict the likelihood of crashes. Supervised machine learning models can predict the probability of RTCs associated with driver errors, allowing road authorities to target enforcement efforts and implement interventions in high-risk areas [26]. These models can be used to identify factors such as speeding, distracted driving, and impaired driving that contribute to crashes. Machine learning techniques can help analyze spatial trajectories of vehicles and identify abnormal turning paths, allowing road authorities to identify dangerous intersections and implement safety improvements [27]. By analyzing vehicle movements, machine learning algorithms can identify patterns that are associated with a higher risk of crashes.

Artificial intelligence (AI) and data analytics have the potential to revolutionize speed management, enabling more proactive and effective strategies for reducing crashes and improving road safety. Real-time crash risk prediction models aim to identify pre-crash conditions for active traffic safety management, allowing road authorities to intervene before crashes occur [28]. By analyzing real-time data on traffic flow, weather conditions, and other factors, these models can predict the likelihood of crashes and trigger interventions such as variable speed limits and dynamic message signs. The Wasserstein Generative Adversarial Network (WGAN) can address the class imbalance problem in model development, improving the accuracy and reliability of crash risk prediction models [28]. This technique can be used to generate synthetic data that balances the number of crash and non-crash cases, improving the performance of machine learning algorithms. AI and data analytics can enhance speed management policies by promoting smoother driving behavior, reducing aggressive acceleration and deceleration, and improving overall traffic flow [29]. By analyzing data on driver behavior, road authorities can identify patterns of aggressive driving and implement targeted interventions to promote safer driving habits.

10. Conclusions and Future Directions

Speed management strategies, encompassing both conventional and advanced measures, play a crucial role in reducing road traffic crashes and improving road safety outcomes. Speed management strategies, including conventional and advanced measures, play a crucial role in reducing road traffic crashes, highlighting the importance of implementing a comprehensive approach [1]. By combining traditional methods such as speed limits and enforcement with innovative technologies like variable speed limits and intelligent speed adaptation, road authorities can create a safer road system for all users. Speed cameras, variable speed limits, and traffic calming measures have shown effectiveness in reducing speeds and improving safety, demonstrating the potential of these strategies to save lives and prevent injuries [16]. These measures can be particularly effective in urban areas and residential neighborhoods, where pedestrian and cyclist activity is high. The Safe System approach provides a comprehensive framework for managing speed and minimizing road traffic injuries, emphasizing the need for a holistic and integrated approach that addresses all aspects of road safety [9]. By adopting a Safe System approach, road authorities can create a road system that is more forgiving of human error and minimizes the severity of crashes when they do occur.

Despite the progress that has been made in speed management, there are still significant gaps in current research that need to be addressed. There is a need for more holistic approaches capturing the complexity of transport in LMICs, recognizing that road safety is influenced by a wide range of factors, including economic development, social norms, and cultural values [21]. Future research should focus on developing and evaluating interventions that are tailored to the specific needs and contexts of LMICs. There is a lack of research on the effects of speed limit changes on emissions, especially in LMICs, highlighting the need for more studies that examine the environmental impacts of speed management strategies [29]. By understanding how speed limits affect emissions, road authorities can make more informed decisions about speed management policies. Further research should extend safety performance indicators to the national level and test the effectiveness of recommended strategies, allowing for a more comprehensive assessment of road safety outcomes [24]. This research should also focus on developing and validating new safety performance indicators that capture the full range of factors that contribute to road safety.

Future research and policy efforts should focus on several key areas to further enhance the effectiveness of speed management strategies. Future work should develop statistical approaches to public health interventions that incorporate variables from multiple outcomes, allowing for a more comprehensive assessment of the impacts of speed management strategies [30]. This research should also focus on developing methods for quantifying the uncertainty associated with these estimates. Policy makers should consider the potential benefits of speed management policies and promote smoother driving behavior, recognizing that these strategies can not only reduce crashes but also improve air quality and reduce fuel consumption [29]. By implementing policies that encourage safer and more efficient driving, road authorities can create a more sustainable transportation system. Further studies are needed to assess the long-term impacts of speed management strategies and their cost-effectiveness, providing decision-makers with the information they need to make informed choices about road safety investments [5]. This research should also focus on identifying the most cost-effective strategies for achieving specific road safety goals.