ANALYSIS OF TRAFFIC SPEED RESPONSE TO DISPLAY OF DYNAMIC MESSAGE SIGN MESSAGES

摘要

The State of Maryland owns and operates over 80 highway Dynamic Message Signs (DMS).When real-time travel time messages began appearing in January, 2010, users and media outletsrenewed historical complaints that DMSs cause localized traffic impacts due to vehicles slowingdown to read the messages. In order to investigate these claims, highway speed data frompermanently mounted Remote Traffic Monitoring Sensors (RTMS) in close proximity to DMSswas collected along with message logs for analysis. Two methods were used: consecutive 5-minute average and aggregate 2-week analysis. In the former, speeds in consecutive 5-minuteperiods in which the DMS condition changed from off to on, on to off, or switched from onemessage to another were compared using paired t-tests. The 2-week analysis consisted ofaveraging traffic speeds over 2-week periods during different DMS operational conditions andmessage types. The findings from 2,268 cases in the first analysis indicated that in the majorityof cases, traffic is not negatively affected by appearance, removal, or change of DMS messages.When negative effects were observed, danger or warning messages had the most influence. The2-week analysis also showed that danger and warning messages had the largest impact on trafficspeeds over longer periods. The message type that included travel time messages, Type 2,showed lower impacts on traffic speeds and in most cases speeds were at or above the postedspeed limit. Overall, the claims that Dynamic Message Signs cause congestion and speedreductions seem to be unsupported in the majority of cases (253 words).