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.
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.
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.
This report is intended to be a primer on the characteristics that affect the design, use and operations of changeable message signs (CMSs), and to provide guidance on the selection of the appropriate type of CMS display. Guidelines on the selection and design of CMS messages are presented in a companion report, Report No. FHWA/TX-92/1232-10 entitled "Guidelines on the Selection and Design of Messages for Changeable Message Signs". This report is an update and consolidation of the following reports: (1) C.L. Dudek and R.D. Huchingson, "Manual on Real-Time Motorist Information Displays", FHWA-IP-86-16, August 1986; (2) C.L. Dudek, "Guidelines on the Use of Changeable Message Signs", FHWA-TS-90-043, May 1991; and (3) C.L. Dudek, "Portable Changeable Message Signs at Work Zones", FHWA/TX-85/07+292-4, July 1984
"This report completes and updates the first edition of NCHRP Report 600: Human Factors Guidelines for Road Systems (HFG), which was published previously in three collections. The HFG contains guidelines that provide human factors principles and findings for consideration by, and is a resource document for, highway designers, traffic engineers, and other safety practitioners."--Foreword.
"This synthesis will be of interest to traffic engineers in federal, state, provincial, and local transportation agencies who are responsible for the design and operation of safe and efficiency highway systems. It will also be useful to consulting traffic engineers, sign manufacturers, and vendors in the private sector who assist governmental clients in the application of changeable message sign (CMS) and other intelligent transportation systems (ITS) technology. It is an update of NCHRP Synthesis no. 61 (1979)."--Avant-propos.
This report is a summary of some of the information that was assembled and presented in final report FHWA-TS-90-043 entitled, "Guidelines on the Use of Changeable Message Signs". This summary report focuses on matrix-type CMSs, with particular attention to the newer light-emitting signs. Although there are many types of new and emerging CMS technologies, CMSs that have actually been installed for highway applications are emphasized.
