Vehicle speeds decreased significantly in work zones where DMSs were used to inform drivers upstream.
Results of two case studies on rural interstates in southeast Missouri.
Made Public Date


Southeastern Missouri
United States

Evaluating the Benefits of Dynamic Message Signs on Missouri's Rural Corridors

Summary Information

The rural deployment of dynamic message signs (DMSs) has been more limited than its deployment in urban areas because of the more dynamic nature of traffic conditions and heavier traffic volumes. However, Missouri Department of Transportation (MoDOT) was awarded a rural safety improvement program (RSIP) grant in 2008 to deploy DMSs and closed-circuit television (CCTV) cameras on some rural segments of highway in the southeast region of Missouri. The University of Missouri performed an evaluation of the deployments with a focus on obtaining the perception of motorists toward DMSs in rural areas, evaluating the impact of DMSs in alerting drivers of an upcoming work zone, and evaluating the impact of DMSs in diverting traffic to a detour route during full freeway closure.

In order to determine the effectiveness of DMS messages on travel speeds in work zones on rural, uncongested four-lane interstates, two forty foot long virtual speed traps were set up to measure vehicle travel speeds. The first speed trap was positioned far enough upstream of the DMS that drivers would not have been able to read the message. The second speed trap was placed far enough downstream from the DMS for drivers to have sufficient time to react to the message on the DMS about the upcoming work zone. This test was conducted in two locations in southeast Missouri on two different dates, June 25 and August 10, 2010, where the posted speed limit is 70 mph.

With the exception of isolating trucks from the sample on June 25th, all reductions in speed are considered statistically significant. For all vehicles (private and trucks combined), there was a speed decrease of 3.64 mph on June 25th and 1.25 mph on August 10th. These results indicate that use of DMS has a positive effect on drivers' speeds upstream of work zones on rural, uncongested four lane interstates. More detailed results can be found in the tables below and full results can be found in Table 3 of the report.

Vehicle Count (upstream/downstream)Upstream Avg. Speed (MPH)Downstream Avg. Speed (MPH)Speed Difference (MPH)
Combined (Total)96274.6270.983.64**
Table A: Results from Case Study 1 (June 25, 2010)

Vehicle Count (upstream/downstream)Upstream Avg. Speed (MPH)Downstream Avg. Speed (MPH)Speed Difference (MPH)
Combined (Total)113270.6969.441.25**
Table B: Results from Case Study 2 (August 10, 2010)

** = Result is statistically significant.
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