Maryland State Highway Administration (SHA) has a rich data archive of the messages posted to the Dynamic Message Signs (DMS) and the time stamps when they were posted and taken down. The archive also contains traffic information surrounding the DMS signs, such as traffic volumes and speeds from various point or probe-based sensors. In this project, the research team used this data archive to study the impact of DMS messages on traffic conditions. Multiple Bluetooth sensors were deployed on a major travel corridor in the Baltimore Metropolitan Area to determine vehicle travel times and to monitor traffic diversions.
Between 2010 and 2020, many transportation agencies began displaying safety messages and crash facts to the traveling public using roadside dynamic message signs (DMS). The content of these messages varies from annual crash and fatality statistics to more detailed messages regarding specific driving behaviors or risk factors. Despite the widespread use of DMS for safety messaging purposes, evaluations of potential impacts on driver behavior and resultant impacts on traffic safety have been limited. This research addresses this gap through a series of investigations to determine the degree to which the use of DMS for safety messages impacts various aspects of driver behavior. Driver behavior was examined in response to different DMS messages while considering critical contextual factors, such as the type of messages displayed, traffic flow conditions, and roadway geometric characteristics. The first set of field evaluations examined driver behavior as vehicles approached in-service emergency and MDOT service vehicles parked on the roadway shoulder in consideration of the state's move-over law. Compliance was measured in terms of speed reduction and lane selection and comparisons were made based upon a series of targeted messages displayed on upstream DMS. Logistic regression models were estimated to assess driver compliance with the law while considering important contextual factors, such as the type of vehicle on the shoulder and the message displayed on the DMS. The results indicate that drivers were more likely to move over or reduce their speeds when a police car was parked on the shoulder as compared to a transportation agency pickup truck. In general, the type of message displayed had minimal impact on driver behavior. The one exception showed that drivers were less likely to exceed the speed limit when targeted move over messages were shown as compared to standard travel time messages. For all message types, both speed and lane compliance were improved if the roadside vehicle was a police car. The second study examined cell phone use rates in consideration of enforcement activities that were conducted in conjunction with the display of targeted safety messages on roadside DMS. The results showed that cell phone use rates were lower during and, particularly, after the enforcement activities were conducted. Use rates were also found to vary based on age, gender, and race, allowing for the identification of target groups for public awareness and outreach campaigns. Cell phone use rates were also lower at freeway exit ramps compared to signalized and stop-controlled surface street intersections. Furthermore, cell phone-specific safety messages were associated with lower use rates than other message types.Ultimately, the findings largely reinforce federal guidance on the use of DMS for secondary purposes, which include displaying road safety messages. As a stand-alone measure, DMS provide marginal impacts on driver behavior. Such messaging strategies are likely to be more effective when used as a part of active safety campaigns with a limited duration as compared to more frequent and continuous display of generic message types. The outcome of the field investigations also shows that combining targeted messaging with the presence of enforcement results in the most substantive improvements in driver behavior.
Dynamic message signs (DMS) are used in conjunction with other media to communicate traffic conditions, general information, and recommended diversion strategies to motorists. Previous studies using loop detector data to estimate diversion rates attributable to advisory messages on DMS have found that diversion is minimal when vague messages are displayed or a distant alternate route is the only option. For motorists traveling on I-95 through Richmond in the Virginia Department of Transportation's Central Region, however, when DMS alert motorists of incidents, I-295 serves as a comparable alternate route, adding no significant travel time to through trips. This scenario provides the opportunity to evaluate the effectiveness of DMS in traffic diversion without the major concerns of added trip time and the quality of the route. This study investigated the impacts of existing message strategies to determine messages that maximize diversion for specific circumstances and to develop new messages for future deployment. An analysis was done for various message types and split into two diversion scenarios: (1) an incident on the primary freeway, I-95, encourages diversion of I-95 traffic to an alternate route, I-295; and (2) an incident on an intersecting freeway, I-295, encourages exiting I-295 traffic to remain on I-95 as an alternate route. The results showed trends where the use of particular words in messages is more effective than the use of others in achieving diversion when percentage of diverted traffic was used as the performance measure. The effects on traffic flow by drivers' reactions to non-traffic messages were also investigated. Transportation agencies are frequently asked to post public service announcements on DMS when they are not being used for traffic-related purposes. It has been suggested that these messages are a distraction to drivers and result in queuing, creating mobility and safety hazards. An analysis that used speed as the performance measure showed minimal impacts on traffic flow from the display of non-traffic messages during weekday non-peak hours. The study recommends that (1) travel time estimates for both the primary and alternate routes or the length or time of the delay be provided on DMS; (2) specific wording, as noted in the text, be used to induce diversion or simply to provide information; (3) messages be displayed in "title case" instead of "ALL CAPS" (i.e., all letters in a word are capitalized) for low-frequency messages; and (4) left-justified or "staircase" messages be used. Further, non-traffic messages should be one-phase messages and should be displayed only during non-peak periods to minimize the potential for queuing. If the recommendations of this research are implemented, the enhanced effectiveness of diversion strategies will result in reductions of delay, fuel consumption, and emissions, as well as the potential for secondary accidents created by major incidents and other traffic flow disruptions. In 2007, the cost of delay for motorists in Richmond, Virginia, resulting from incidents was estimated at $119 million. A modest 1 percent reduction in this cost attributable to better diversion strategies that use DMS more effectively would result in an annual cost savings to VDOT of more than $1 million.
The objective of this research project was to determine appropriate guidelines and methodology for evaluating dynamic message sign (DMS) performance. National literature reviews and agency surveys were conducted and synthesized for a critical assessment of the state-of-the practice in DMS performance evaluation. DMS performance metrics were established based upon data availability, time of evaluation (pre-post)), and environment of application (urban/rural). Both qualitative and quantitative DMS benefits were established with examples of associated analysis tools given and discussed. Case studies were conducted along freeway corridors where DMSs had been implemented in both urban (Houston, Texas) and rural (Amarillo, Texas) environments. The results of these case studies highlighted constraints in both data availability and appropriate analysis procedures. Final guidelines and methodology for DMS performance evaluation were produced emphasizing the limitation to assessment of both qualitative and quantitative benefits. A guidebook of DMS performance evaluation procedures was included as Appendix D in the research report.
This research used a fixed-base driving simulator to determine the effects of dynamic message signs (DMSs) on driver behavior. A DMS notifies drivers with safety, weather, incident, or traffic condition messages. Recently, however, state Departments of Transportation (DOTs) display safety messages with entertaining content. The Kansas DOT (KDOT) wanted to assess how these entertaining messages affect driving behavior. Therefore, this research evaluated the effect of DMS content on driver behavior using a combination of surveys and driver behavior data obtained from a fixed-base driving simulator. Existing literature was reviewed to determine similar studies. Based on the literature, which included results of DMS modeling in driving simulators and DMS effects on driver behavior, a research methodology was developed. One hundred participants were recruited and screened using an online survey questionnaire that included messages currently displayed on DMS; feedback on their perceived effectiveness was requested. The second data collection was done via a driving simulator experiment. The simulator was prepared for the study, the DMS was set, and events were designed to capture changes in driver behavior and awareness. A total of 60 participants with diverse demographics drove by several DMSs that displayed a variety of messages. Participants completed a survey at the end of the experiment, and their responses were compared to responses of the online survey. Behavioral data (speeds, accelerations, gazes, etc.) were then reduced, and statistical analyses were performed, including hypothesis testing and analysis of variance, to evaluate to what extent the message content affected driver behavior. The study identified potential messages that were found to effectively affect driver behavior.
(Cont.) Evaluation is done by developing a tool using the 'closed loop' integration between MITSIMLab, a microscopic traffic simulator as a proxy for the real traffic conditions, and DynaMIT, a DTA tool that is capable of generating predictive and consistent guidance. Using Genetic Algorithms with the 'closed loop' setup, a methodology is developed to identify VMS locations that result in the best consistent guidance to drivers. A case study is presented showing the benefits of using VMS by simulating incidents of major severity in Lower Westchester County, NY. Application of optimal location methodology and associated advantages in solving the problem is demonstrated with the help of a case study on a synthetic network. Results illustrate the potential and significant benefits obtained through Variable Message Signs. Using the optimal location methodology can improve these benefits even further.
Further research into how the warning message is presented or worded could provide additional insight into the impact it can have on driver behavior. Since it is observed that drivers acknowledge the 'reduce speed' advisement, it is likely that specifying a specific speed limit could also warrant driver obedience. Additional testing and observation of driver reaction to larger traffic volumes and situations within the fog would also allow for further analysis of driver behavior under reduced visibility and the impact the early warning system has on their behavior.
