Garg, Roma (2003-05). Impacts of a conspicuity treatment on speed limit compliance. Master's Thesis. Thesis uri icon


  • In reduced speed zones, where no other cues indicate the need to slow down, drivers sometimes fail to notice the standard Speed Limit sign and may be speeding inadvertently. To help reduce inadvertent speeding, a red border was installed around the Speed Limit sign in seven reduced speed areas and the impacts of the increased conspicuity on speed limit compliance were measured. The general study approach was to collect and compare speed data for a standard sign (before condition) and a red border sign (after condition). The short-term effects of a modified red border sign, which was achieved by replacing the thin black border of the standard sign with a four inch wide red border, were evaluated at four sites. Results of this modified border study indicated that there was a statistically significant reduction in the mean speeds as well as in the 85th percentile speeds for the red border sign conditions, however the reductions were not practically significant. This study also evaluated the effect of using a higher conspicuity sheeting material at two sites. The results indicated that use of higher conspicuity sheeting has some benefits for the standard sign but no additional benefits for the red border sign. The added border study evaluated the long-term effects (approximately nine to eleven months after the treatment) of adding a three inch wide red border to the standard Speed Limit sign at three sites. The results of this study indicated that impacts of the red border treatment increase with passage of time. The mean speeds decreased by 8.1 percent and the percent of vehicles exceeding the speed limit (55 mph) decreased by 21.7 percent. The decreases in speeds were both statistically and practically significant. A comparison of the thesis study with other similar studies found in literature shows comparable benefits of the red border sign with other speed management measures. Based on the results for long-term effects, use of the red border Speed Limit sign is recommended in reduced speed zones where inadvertent speeding is common.

publication date

  • May 2003