Studies have shown that the traffic flow on a two-lane road adjacent to a school can be described by the Green shields model. A length of 0.5 mi adjacent to a school is described as a school zone (see Figure 6.19) and operates for a period of 30 min just before the start of school and just after the close of school. The posted speed limit for the school zone during its operation is 20 mi/h. Data collected at the site when the school zone is not in operation show that the jam density and mean free speed for each lane are 118 veh/mi and 63 mi/h. If the demand flow on the highway at the times of operation of the school zone is 95% of the capacity of the highway, determine:

(a) The speeds of the shock waves created by the operation of the school zone

(b) The number of vehicles affected by the school zone operation

(c) The time the queue takes for it to dissipate after the operation of the school zone

 

0.5 mile School Zone