Variable Message Signs Research Articles

Variable Message Signs in Traffic Management: A Systematic Review of User Behavior and Future Innovations

Effective traffic management is crucial in addressing the growing complexities of urban mobility, and variable message signs (VMSs) play a vital role in delivering real-time information to road users. Despite their widespread application, there is limited comprehensive understanding of how VMS influence user behavior and optimize traffic flow. This systematic literature review aims to address this gap by examining the effectiveness of VMS in shaping user interactions and enhancing traffic management systems. Using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology, a thorough analysis of relevant studies was conducted to identify key factors influencing VMS impact, including message content and characteristics, complementary sources of information, user demographics, VMS location, and users’ reliance on these signs. Additionally, the review explores the implications of displaying non-critical information on VMS and introduces virtual dynamic message signs (VDMSs) as an innovative approach for delivering public traveler information. The study identifies several research gaps, such as the integration of VMS with vehicle-to-everything (V2X) technologies, navigation systems, the need for validation in real-world scenarios, and understanding behavioral responses to non-critical information on VMS. This review highlights the importance of optimizing VMS for improved user engagement and traffic management, providing valuable insights and directions for future research in this evolving field.

Audiovisual messages may improve the processing of traffic information and driver attention during partially automated driving: An EEG study

Partially autonomous vehicles can help minimize human errors. However, being free from some driving subtasks can result in a low vigilance state, which can affect the driver’s attention towards the road. The present study first tested whether drivers of partially autonomous vehicles would benefit from the addition of auditory versions of the messages presented in variable message signs (VMS), particularly, when they find themselves in a monotonous driving situation. A second aim was to test whether the addition of auditory messages would also produce an indirect effect on the driver’s vigilance, improving performance on other driving subtasks not related to the message processing. Forty-three volunteers participated in a driving simulator study. They completed two tasks: (a) a VMS task, where they had to regain manual control of the car if the VMS message was critical, and (b) a car-following task, where they had to pay attention to the preceding car to respond to occasional brake events. Behavioral and EEG data were registered. Overall, results indicated that the addition of audio messages helped drivers process VMS information more effectively and maintain a higher level of vigilance throughout the driving time. These findings would provide useful information for the development of partially automated vehicles, as their design must guarantee that the driver remains attentive enough to assume control when necessary.

Review of Risk Assessment Methods for Cybersecurity Attacks on Road Network and Intelligent Transportation System Applications

One of the most discussed infrastructure issues of our time is cybersecurity. A transportation system that connects not only people but also logistics to make the community around the world closer is one of the critical infrastructures requiring cybersecurity to perform its functions. Transportation systems include aviation, maritime, pipeline, railroad, and road networks. This study focuses only on the roadway network system. Cutting-edge technologies related to highway networks, such as variable message signs, vehicular ad hoc networks, and in-vehicle networks, have been developed to improve safety and efficiency. Those technologies make transportation systems more complex and integrated, bringing many potential vulnerabilities and cyber risks. This can attract an adversary to attack and exploit the system. The number of cybersecurity attacks on transportation systems has been growing for many years. However, it is not feasible to protect against all cybersecurity attacks in the system. The risk assessment concept is proposed to prioritize risk resulting from attacks to support decision-makers in formulating appropriate policies or countermeasures. This study reviews risk assessment methods for cybersecurity attacks on road networks and intelligent transportation system applications. Three potential risk assessment methods are examined for road network systems: the National Institute of Standards and Technology Special Publication 800-30, Attack Potential and Damage Potential, and the fuzzy analytic hierarchy process.

Effects of passing rates on driving behaviour in variable speed limit-controlled highways: Evidence of external pressure from a driving simulator study

Variable message signs on motorways can show dynamically changing speed limits for traffic safety or efficiency reasons. While the effects of variable speed limits have been studied in the literature, the effect of (drivers in) vehicles operating under different speed limit information − caused by transitioning from one speed limit to another − has received relatively little attention. During such a transition, drivers can either be overtaken by vehicles operating under a higher speed limit, or conversely, drivers overtake slower vehicles operating under a lower speed limit. In both scenarios, opposite forms of external pressure are expected to be exerted by the surrounding traffic. Sixty-seven participants performed three randomised drives (201 drives in total), each reflecting one of three different passing rates scenarios, i.e., the number of vehicles overtaking the driver, or vice versa, caused by a speed limit change. Passing rates varied from as low as 90 veh/h to as high as 360 veh/h. Increasing passing rates act as a proxy for increasing levels of external pressure applied to drivers. Statistical analyses are conducted using a Linear Mixed Model (LMM) and a Generalised Estimating Equations (GEE) approach, accounting for correlation caused by the panel nature of the data. The LMM indicates that the driving behaviour indicators are indeed affected under different passing rates and that these differences are statistically significant. Results indicate that drivers in higher passing rate scenario(s) tend to accelerate and drive faster compared to the low(er) passing rate scenario(s). Further, the GEE model for speed selection indicates that drivers from different age groups and gender select different speeds in response to the impact of external pressure caused by surrounding traffic. Similarly, the GEE model for speed variation within a driver suggests differential speed variations of age groups and gender under different passing rates. Overall, this study finds pronounced effects directly related to the imposed external pressure via the surrounding traffic, where high passing rates lead to significant speed variations that increase the chances of drivers engaging in safety-critical events.

Legibility of variable message signs on foggy highway: Effect of text color and spacing

Variable message signs are frequently utilized as highway communication facilities to inform vehicles about the state of the roads and the weather. However, standards and design specifications for variable message signs are unclear. This study examines the effect of the own factors and environmental factors on the legibility of variable message signs in order to optimize the design of variable message signs on highways. Three font colors (green, red, and yellow) and three levels of word spacing (0.1H, 0.3H, and 0.5H) were chosen for the variable message signs. For the environmental factors, three different weather types were represented according to visibility, namely sunny (visibility 10,000 m), light fog (visibility = 1000), and heavy fog (visibility = 200). The legibility time and distance were recorded for 23 participants, and then the legibility of the variable message signs was analyzed. The results showed that own factors and environmental factors influenced the legibility of the variable message signs. Experiment 1 results showed that the legibility of the variable message signs was the best when the text was yellow in light fog weather conditions. Experiment 2 results showed that the legibility of the variable message signs was better than other experimental scenarios in light fog conditions with a 0.3H word spacing. The findings of this study will be used by relevant agencies to establish design guidelines for variable message signs.

Investigating the feasibility of dynamic speed limit on Indian highways

Speed limits that change as per real time traffic, road, and weather conditions are termed as Dynamic Speed Limits (DSL). Road users are informed of speed limit changes in DSL scheme by electronic signs or Variable Message Signs (VMS) placed above the lanes or side-mounted along highways. In India, most of the highways have static speed limits. The speed limits are kept lower at locations or stretches adjacent to roadside schools, market areas, bus stops and intersections, for enhancing safety of Vulnerable Road Users (VRUs). This causes higher travel time to through traffic while travelling through these stretches. DSL has the potential in reducing the travel time and the variability of speed of vehicles, thus helps in enhancing road safety. The present work investigates the feasibility of DSL on various segments of a typical Indian highway passing through various roadside developments and human activities using cost-benefit analysis. The travel time benefits due to DSL are estimated by comparing the travel times with static and dynamic speed limit conditions. The results indicate that there is a significant amount of saving in aggregate travel time of all vehicles passing through the stretch due to the application of DSL. The benefit cost ratios greater than unity indicated that it is beneficial to deploy DSL on several segments of the highway passing through roadside schools, market areas, bus stops and intersections. The Benefit-Cost Ratio is also used advantageously to prioritize viable locations for deployment of DSL. The findings from the present work are likely to be of interest to policy makers in different developing countries where infrastructure/facilities for VRUs are deficient, road safety is a major concern and speeding is identified as a major problem.

Audiovisual presentation of variable message signs improves message processing in distracted drivers during partially automated driving

Introduction: Highly automated driving is expected to reduce the accident risk occurrence by human errors, but it can also increase driver distraction. Previous evidence shows that auditory signals can help drivers take over in critical situations. However, it is still uncertain whether the potential benefit of verbal auditory signals could be generalized to driving situations where drivers are visually and auditorily distracted. Method: Our first objective was to compare the effectiveness of complementary audio messages (audio + visual condition) and visual only (visual condition) variable message signs (VMS) messages. The second objective was to explore the potential use of oral messages with traffic information to help highly-automated vehicle drivers identify critical situations. Eye-tracking data were also registered. Twenty-four volunteers participated in a driving simulator study, completing two tasks: (a) a TV series task, where they had to pay attention to an episode of a TV series while traveling along the route; and (b) a VMS task, where they had to recover the manual control of the car if the VMS message was a ‘critical message.’ Results: General results showed that, when the audio was available, the participants: (a) had a higher ability to discriminate the VMS messages, (b) were less conservative, (c) responded earlier, and (d) their pattern of fixations was more efficient. A complementary analysis showed that the counterbalance order was a moderating factor for the discrimination ability and the response distance measures. This evidence suggests a potential learning effect, not cancelled by counterbalancing the order of the conditions. Conclusion: The processing of traffic messages may improve when provided as oral and visual messages. Practical Applications: These results would be of special interest for engineers designing highly automated cars, considering that the design of automated systems must ensure that the driver's attention is sufficient to take over control.

Bi-objective simulation optimization for online feedback control of variable speed limits considering uncertain traffic demands and compliance behaviors

Abstract Variable Speed Limits (VSL) stand out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways. It allows Variable Message Signs (VMSs) to dynamically determine the speed limits according to real-time traffic states. This paper introduces an innovative online feedback control approach designed to regulate speed limit values on Variable Message Signs (VMSs), addressing multiple bottlenecks while considering their spatiotemporal constraints. Moreover, we offline optimize the gain coefficients of this feedback control approach in the simulation-based optimization (SBO) framework. Specifically, with average and variance of space-mean speeds as bi-objectives, a stochastic SBO model considering uncertain traffic demands and compliance behaviors is established and solved by a bi-objective surrogate-based promising area search (BOSPAS) algorithm. Real-field experiments conducted in Edmond City demonstrate the well-performing bi-objectives of the proposed approach, especially in handling uncertain compliance behaviors and traffic demands. Compared with the uncontrolled scenario, the feedback control schemes with the offline optimized gain coefficients improve the average and variance of space-mean speeds by up to 16.2% and 20.8%, respectively. Meanwhile, by the comparison of detailed performances, it is found that the optimized control schemes perform better than the uncontrolled scheme from the overall and local aspects. In conclusion, this study puts forward a general framework that applies an online feedback control approach with gain coefficients optimized offline by an SBO method to deal with real-time decision-making problems under uncertainties.

Life-saving Signs

Energy- and cost-efficient variable message signs from Triplesign swiftly adapt to real-time traffic dynamics, updating within three seconds to provide timely and accurate information

Effects of Letter Size and Luminance on the Legibility of Variable Message Sign Under Foggy Weather Conditions

Effects of Letter Size and Luminance on the Legibility of Variable Message Sign Under Foggy Weather Conditions

Proactive Coordination of Traffic Guidance and Signal Control for a Divergent Network

In the realm of transportation system optimization, enhancing overall performance through the proactive coordination of traffic guidance and signal control in a divergent network can tackle the challenges posed by traffic congestion and inefficiency. Thus, we propose an innovative approach to first allow the information on variable message signs (VMS) that deviates from estimated travel times. This proactive approach guides drivers towards optimal routes from a system-wide perspective, such as minimizing vehicle hours traveled. The deviation is constrained both by the lower bound of drivers’ long-term compliance rate and the upper bound of the favored traffic signal operation. The proposed approach coordinates the traffic guidance system with the signal control system. The traffic signal control system sets the upper limit for information deviation in the traffic guidance system, while the traffic guidance system provides demand predictions for the traffic signal control system. Overall, the objective function of the approach is the network-level performance of all users. We gauge traveler satisfaction as a measure of system credibility, using both a route choice module and a satisfaction degree module established through stated preference surveys. Numerical results demonstrate that proactive-coordinated (PC) strategies outperform reactive-coordinated (RC), proactive-independent (PI), and reactive-independent (RI) strategies by improving the system performance, meanwhile keeping the system trustworthy. Under the normal traffic scenario, the PC strategy reduces total travel time by approximately 10%. Driver satisfaction with the PC strategy increases from a baseline of 76% to 95%. Moreover, in scenarios with sudden changes in either traffic demand or supply, e.g., accidents or large events, the proactive guidance strategy is more flexible and can potentially improve more from the system perspective.

A Resilience Analysis of a Motorway Tunnel Affected by a Traffic Accident Using the Average Vehicles’ Speed as a Metric

Given the role of road tunnels in a road network, it is relevant to quantitatively assess their resilience due to disruptive events. In this respect, the travel speed of traffic flow, as a metric of resilience, in the event of traffic accidents in road tunnels has been scarcely used. This represents a gap of knowledge that this paper intends to fill. For the purpose, the research method applied involves the development of a traffic macro-simulation model, and the analysis of results using the average travel speed and its spatial profile as a resilience metric. Particularly, we have evaluated the resilience of a twin-tube motorway tunnel when a traffic accident occurs in a tube. The findings showed how the best functionality level of the system, expressed in terms of average vehicles’ speed, with its related greatest resilience index, is associated with the partial closure of the disrupted tube rather than the complete one. Further benefits might be obtained by activating Variable Message Signs (VMSs) that alert only the Heavy Goods Vehicles (HGVs) to exit the motorway before entering the tunnel and to use an alternative itinerary identified in the nearby transportation network. In this respect, we found that by means of the activation of VMSs as a traffic control strategy, the resilience index increased by about 7–17% when the traffic accident caused the partial closure of the disrupted tube for 1–3 h. Improvements might also be achieved by rapidly opening the two traffic by-passes at the tunnel portals that allow for the use of the adjacent undisrupted tube for two-way traffic. The unavailability of an alternative itinerary in the nearby transportation network along which to re-route the HGVs is also examined, finding a reduction in the functionality conditions of the system. The results obtained might serve as a support tool in the choice of functional recovery strategies in the case of the temporary partial or complete block of a tunnel tube due to a traffic accident.

Effects of highway work zone temporary countermeasures

Highway work zones are associated with significant adverse impacts on safety. Mitigating these impacts can be achieved by implementing several countermeasures. This paper uses controlled experiments in a driving simulator to investigate the effects of physical and digital temporary traffic control countermeasures on work zone safety. These include variable message signs, dynamic speed displays, rumble strips, and lane widths. 116 participants were recruited for the experiment. A linear mixed-effects model was developed to capture the effects of these countermeasures on average travel speed and standard deviation of speeds in the advanced warning area and within the work zone itself. The results reveal that rumble strips installed within the work zone cause the strongest reduction in speeds. Narrower lanes cause smaller speed reductions. In general, the effects of temporary traffic control countermeasures on speeds were local and were not retained beyond their proximity.

Evaluating the impacts of vehicle-mounted Variable Message Signs on passing vehicles: implications for protecting roadside incident and service personnel

This study aims to evaluate the Variable Message Signs (VMS) mounted over the cab of emergency vehicles as a safety countermeasure to protect roadside incident and service personnel. The research team collaborated with the Alabama Department of Transportation’s Safety Service Patrol (SSP) program, specifically the Alabama Service Assistance Patrol (ASAP) in the West Central Alabama region, to collect video data from their service vehicles. Deep learning techniques were employed to detect vehicles in the recorded videos. A total of 11,338 passing vehicles were detected in 135,946 frames of video footage, and their trajectories were extracted for analysis. The study focused on examining the behaviors and movements of passing vehicles, including their speed and lane change behaviors, and developed statistical models to systematically investigate the impact of VMS on these behaviors. Random intercept models were utilized to account for unobserved factors associated with different stop locations. The modeling results revealed significant relationships between the use of VMS and the behaviors of passing motorists. When the VMS was active, drivers were more likely to change lanes and reduce their speed compared to situations where the VMS was not active. The odds of a vehicle changing lanes were found to be 95% higher when the VMS was in use. These findings suggest that the utilization of VMS can have a positive impact on traffic, particularly for passenger vehicles. The study outcomes imply that the use of VMS could be an effective countermeasure in protecting roadside incidents and ensuring the safety of service personnel.

Analysis of drivers’ preferences toward content and message format of variable message signs during tunnel emergency evacuation: A case study of Niayesh tunnel in Tehran

In the event of an emergency evacuation of a tunnel, variable message signs are one of the tools available to tunnel operators to communicate with tunnel users and play an important role in guiding them. In this study, the primary focus is to determine the most appropriate message for variable message signs in terms of content and format for tunnel emergency evacuations. This study evaluates the responses of drivers to the visual comparison between variable message signs by using stated choice methods. Using a binary logit model, the results indicate that drivers prefer the text message “Turn off the car, exit the tunnel” in two lines on the right side of the sign along with the green image of the emergency exit on the left side. Therefore, it is anticipated that the findings obtained and their application at the time of the tunnel disaster will reduce the likelihood of catastrophic accidents and mitigate their consequences.

Validity of Variable Message Sign Information: Is It Influenced by Drivers’ Short-Term Memory?

Variable message signs (VMSs), as a key component of intelligent transportation systems, have been frequently used in the management of urban roads to provide drivers with real-time traffic information. Nevertheless, a lack of unified regulations for VMS design, makes it difficult to accurately determine the validity of VMS information. In practice, inappropriately designed VMSs (e.g., VMSs overloaded with information and long setting distances) are common. In this study, laboratory simulation trials were conducted to assess VMS information validity in relation to the short-term memory (STM) capacity of drivers. Specifically, drivers capacity to easily obtain and respond correctly to valid VMS information based on memorized target information. Sixty participants completed the trials and pre-/postquestionnaires. Subjective evaluation, dynamic information acquisition rate, accuracy, and memory reliability were analyzed to evaluate their relationship with VMS information validity. The results confirmed that STM considering the information demand rate significantly affected the validity of the VMS information. Information validity deteriorated as the information volume and VMS setting distance increased. Reasonable validity was found when memory reliability ranged between 0.85 and 1.5 and the information volume was no more than 90 bits, corresponding to a subjective evaluation of 1, an accuracy of at least 80%, and a suggested STM time of 43.46 s. These criteria would satisfy driver information demand and prevent information redundancy or wasting of resources. These findings provide a basis for determining the thresholds for VMS information to promote practical and user-friendly VMS designs on urban roads.

도로조명 등주 부착용 경량 가변형 도로전광표지(VMS)의 주 · 야간 판독거리 측정에 관한 연구

In this paper, a lightweight single-sided LED Variable Message Signs(VMS) that can be attached to a street lighting pole and a double-sided LED VMS with a transparent display were manufactured and tested for daytime and nighttime legibility distances, which are most important for LED VMS. As a result of the subjects legibility distance measurement, the average legibility distance of the single-sided LED VMS was 201m during the daytime and 163m at nighttime, which was measured as more than 134m, which is the demand reading distance required on the road at 60㎞/h(4th quartile). In addition, according to the analysis results, there was no significant difference in daytime and nighttime legibility distance by gender within the error, but it was analyzed that the legibility distance increased by about 1.2times during the day than at night.

Safety in Work Zones

The use of variable message signs at road construction sites can help keep workers and drivers safe at all times of the day

A Before-and-After Study of a Collision Risk Detecting and Warning System on Local Roads

Local roads have numerous blind spots caused by complex geometry, obstacles, and narrow width. Thus, conventional proactive countermeasures, such as passive traffic signs and convex mirrors, have not always been effective in preventing local road collisions. In this paper, we present a novel proactive two-step approach for traffic safety on local roads, comprised of detection of pedestrian-to-vehicle and vehicle-to-vehicle collision risks and warning systems. First, using video surveillance and radars to eliminate blind spots, the system detects road objects, predicts their trajectories and reachable areas, and identifies a potential risk situation. Second, it provides road users such as vehicles and pedestrians with warnings through LED variable message signs, which allows them to react effectively in risky situations. We have applied the system to two local road sites in South Korea, including a university campus in Seoul City and an apartment complex in Daejeon City. The detecting system has been validated using a confusion matrix. We have assessed the warning effect through a before-and-after study and found that the proposed system contributed to the improvement of traffic safety at the case study site in that traffic conflicts decreased by 55–62%.

Ubiquitous Control Over Heterogeneous Vehicles: A Digital Twin Empowered Edge AI Approach

The forthcoming of automated driving has led to vehicular heterogeneity, where vehicles with different automation levels, including connected and automated vehicles (CAVs), connected vehicles (CVs) and human-driven vehicles (HVs), coexist in the road traffic. However, the design of current traffic control systems fail to account for the vehicular traffic heterogeneity. In addition, the emerging artificial intelligence (AI) based traffic control strategies require large quantities of computation resources and generate high delay, which cannot meet the faultintolerance requirement of the traffic control system. Therefore, there is an urgent need for constructing a new traffic control framework to jointly satisfy the fault-intolerance requirement and realize ubiquitous control over the heterogeneous vehicles. Inspired by this, a digital twin (DT) empowered edge AI framework is proposed in this article. The DT's virtualization capability is utilized to enable virtual risk assessment and performance analysis under the fault-intolerant traffic control system. In addition, the DT's offline learning capability helps the edge AI understand the road traffic data more intelligently to perform enforced optimizations and decisions. Then, a three-layer vehicle control paradigm is discussed under the proposed framework. In the first layer, deep reinforcement learning (DRL) is utilized to intelligently control the CAV acceleration and lane-changing. In the second layer, indirect CV/HV control can be performed by adjusting the target speed and penetration rate of the DRLcontrolled CAVs which are mixed in the traffic flow. In the third layer, vehicle-to-everything (V2X) communications and variable message signs are utilized to realize the direct control of CVs and HVs. Experimental