A new carpool lane has replaced one lane of an existing six-lane highway. During peak hours, the lane is restricted to cars carrying three or more passengers. After five months of operation, the carpool lane handles 800 autos/h, whereas the existing lanes are operating at capacity levels of 1500 veh/h/ln at an occupancy rate of 1.2. How would you determine if the new carpool lane is successful or if the lane should be open to all traffic?

Question

What will be an ideal response?

Answer 1

This would be a good case to utilize a control versus experimental group analysis.
By comparing the new level of traffic on the carpool highway with that of another
highway without a carpool lane, it can be determined if the carpool lane is a
success.
In order to do this, one must first have traffic statistics for the number of
automobiles and number of persons per hour on the roads before and after the
modification to the facility. Next, one must establish a minimum acceptable rate
of increase in persons traveling by carpool. If the capacity (persons carried per
lane per hour) with the carpool modification is greater than that with natural
growth plus the minimum acceptable rate, the carpool lane program is considered
successful.
Assume the High Occupancy Vehicles (HOV) in the carpool lane carry 3
passengers per vehicle, the average autos carry 1.2 persons, the acceptable rate of
increase is 10% and the growth rate is 4% in the five months.
800(3) = 2,400 > 1,500(1.2)(1 + 0.04) = 1,872
Therefore, the carpool lane is a success.