Speed Reduction Profiles of Vehicles in a Highway Construction Zone

In response to roadway geometry and traffic control devices, motorists may change their speeds within a work zone. Speed profile data were collected for 208 vehicles who traveled a 1.5-mile long section of a work zone, and speed reduction patterns were determined for Autos and Trucks. Four driver categories were identified based on the patterns. About 61% of the drivers reduced their speeds considerably after the first work zone speed limit signs, but nearly 15% of the drivers did not reduce their speeds until they neared the location of construction activities. About 11% of the drivers traveled at consistently high speeds and did not considerably reduce their speeds. The remaining drivers did not display a common pattern. The average speeds of Autos and Trucks were 5-18 mph and 1-12 mph, respectively, over the work zone speed limit. Vehicles decreased their speeds to the lowest level near the work space, but increased them after passing it. Even at the work space, about 65% of Autos and 47% of Trucks traveled faster than the speed limit. Autos and Trucks reduced their speeds by 1-13 mph and 3-12 mph, respectively, compared to their speeds at the beginning of the taper. The speeds at the beginning of the taper were used to group the vehicles into four speed groups. The maximum reduction in the average speed at different locations was greater with greater initial mean speeds; indicating that, on the average, the vehicles with higher initial speeds reduced their speeds more than the vehicles with lower initial speeds. However, the drivers in the higher initial speed groups kept higher speeds in the work zone than the drivers in the lower initial speed groups, even though the former group had greater speed reductions than the latter group.