Study on Speed and Speed Limits of Expressway Work Zones

The speed distribution of each main component of freeway work zones was investigated and analyzed in this study. The following four kinds of freeway work zones were investigated: the closed one-way running lane work zone, the closed one-way passing lane work zone, the closed one-way lane work zone, and the closed one-way transition region work zone. The average speed (i.e. the 85th percent speed), the speed difference, the speed difference between small and large vehicles, and the high-speed vehicles' percentage were then determined for each component. Furthermore, statistical results concluded that moving downstream from the upstream normal area, the warning area (or transition area), and finally through the activity area of work zones, the standard deviation of the speed distribution, as well as the speed difference between small and large vehicles, noticeably decreases. According to the law of vehicle speed distribution, speed control principles, and suggested limited speed values were proposed for each component of freeway work zones based on the characteristic of the speed statistical distributions.