RELATIONSHIP BETWEEN INITIAL SPEED AND SPEED INSIDE A HIGHWAY WORK ZONE

Drivers' speeds in the advance warning area may influence the speeds that they maintain throughout the work zone. The correlations between the speed at the end of the advance warning area and the speed in the work activity area are examined. Vehicles are grouped into six driver categories or subcategories on the basis of their speed profiles. Vehicles were also divided into Fast-, Faster-, Very Fast-, and Fastest-moving groups on the basis of their initial speeds. Vehicles with higher initial speeds, in general, reduced their speeds more than the vehicles with lower initial speeds; however, vehicles in the higher initial speed groups kept higher speeds in the work zone than the vehicles in the lower initial speed groups, even though the former group had larger speed reductions than the latter group. Drivers were classified into the combinations of speed groups and driver categories. The drivers in a category were not distributed uniformly among the four speed groups. Similarly the drivers in a speed group were not distributed evenly among the driver categories. The data showed that the great majority of the drivers who did not reduce their speeds in work zones belonged to the Faster and Very Fast groups. About one-third of the drivers who were extremely speeding (Very Fast and Fastest groups) reduced their speeds and kept reducing them as they traveled in the work activity area. However about one-third of those who were excessively speeding (Fast and Faster groups) reduced their speeds initially, but increased them in the work activity area and then reduced them when they reached the work space.