Speed-Reduction Patterns of Vehicles in a Highway Construction Zone

Drivers may change their speeds at different locations within a work zone in response to roadway geometry and traffic control devices. Speeds of vehicles at different locations within a work zone were determined in this study in order to plot their speed-reduction profiles. Vehicles were followed from the time they entered a 1.5-mi- long study section until they exited from it. Automobiles and trucks showed similar speed-reduction patterns. Four categories of drivers were identified on the basis of these patterns. About 63% of drivers reduced their speeds considerably after passing the first work zone speed-limit signs (Category 1). Nearly 11% of drivers reduced their speeds when they neared the location of construction activities ( Category 2). About 11% of all drivers did not reduce their high speeds (Category 3). The remaining drivers did not indicate a distinct pattern (Category 4). Three distinct speed-reduction patterns were observed for the drivers in Category 1. The first group decreased their speeds near the first speed-limit signs and had further speed reductions at the work space. The second group drove similarly to the first group, but increased their speed between the two points. The third group reduced their speed near the first speed-limit signs and kept that speed until they passed the work space. The average speed decreased as the vehicle approached the work space, but rapidly increased after passing it. Even at the work space, about 2/3 of automobile drivers and more than half of truck drivers exceeded the speed limit.