On a freeway with a flow rate of 3,000 vehicles per hour and a space mean speed of 60 mph, what is the traffic flow density?

To determine the traffic flow density, we can use the formula that relates flow rate, speed, and density. The key relationship is given by:

Density (D) = Flow Rate (q) / Space Mean Speed (S)

In this scenario, the flow rate is provided as 3,000 vehicles per hour, and the space mean speed is given as 60 mph.

By substituting these values into the formula:

D = 3000 vehicles/hour / 60 miles/hour

Calculating this gives us:

D = 50 vehicles per mile

This result indicates that the correct answer is 50 vehicles per mile, which aligns with the answer choice provided. This measure of density helps traffic engineers understand how many vehicles occupy a given length of roadway, which is crucial for assessing traffic flow characteristics and managing roadway performance. Thus, it becomes evident how spacing between vehicles and flow rates directly impact the overall density of traffic on a freeway.