Control of Vehicle Speeds in Temporary Traffic Control Zones (Work Zones) Using Changeable Message Signs With Radar

Studies have shown that most drivers do not slow down in response to the standard regulatory or advisory speed signs that are customarily used to regulate speeds at temporary traffic control zones (work zones). This study evaluated the effectiveness of the Changeable Message Sign (CMS) with a radar unit in reducing speeds at work zones. Four CMS messages designed to warn drivers that their speed exceeded the maximum safe speed were tested at seven work zones on two interstate highways in Virginia. Speed and volume data for the whole population traveling through the sites were collected with automatic traffic counters. To assess the effect of the CMS with radar (on high- speed drivers in particular), vehicles that were traveling above a selected threshold speed triggered the radar-activated display and were videotaped as they passed through the work zones. The data obtained from the videotapes were used to obtain speed characteristics of these speeding drivers as they traversed these study sites. Statistical tests were then conducted using these speed characteristics to determine whether significant reduction in speed accompanied the use of CMS. The results indicate that the CMS with radar significantly reduced the speeds of speeding drivers. The messages used were rated according to their level of effectiveness in the following order: (1) YOU ARE SPEEDING SLOW DOWN, (2) HIGH SPEED SLOW DOWN, (3) REDUCE SPEED IN WORK ZONE, and (4) EXCESSIVE SPEED SLOW DOWN.