How is time between successive vehicles typically calculated?

The time between successive vehicles is typically calculated using the formula that involves the flow rate of vehicles per hour. When traffic flow is measured in vehicles per hour, the time gap between each vehicle can be determined by taking the total number of seconds in an hour, which is 3600 seconds, and dividing it by the flow rate in vehicles per hour.

This calculation gives the time interval (in seconds) that will elapse between one vehicle passing a fixed point and the next vehicle passing that same point. Essentially, this allows traffic engineers to assess and manage the flow of vehicles on roadways effectively, ensuring that they can implement necessary changes to improve traffic flow and reduce congestion.

In contrast, other methods mentioned in the options do not directly yield the time between vehicles in this manner. For instance, spacing divided by flow rate would not represent a direct relationship to time between vehicles without additional context. Similarly, total volume divided by number of vehicles measures something entirely different, as does density divided by speed, which pertains to the speed of vehicles rather than the timing aspect. Thus, dividing 3600 by flow rate is the straightforward and accurate method to determine the time between successive vehicles.