A multilane highway has two northbound lanes. Each lane has a capacity of 1500 vehicles per hour.
Currently, northbound traffic consists of 3100 vehicles with 1 occupant, 600 vehicles with 2 occupants, 400 vehicles with 3 occupants, and 20 buses with 50 occupants each. The highway's performance function is t = t0[1 + 1.15(x/c) 6.87], where t is in minutes, t0 is equal to 15 minutes, and x and c are volumes and capacities in vehicles per hour.
An additional lane is being added (with 1500 veh/h capacity). What will the total person hours of travel be if the lane is
(a) open to all traffic,
(b) open to vehicles with 2 or more occupants only, and
(c) open to vehicles with 3 or more occupants only?
(Assume that all qualified higher-occupancy vehicles use only the new lane, no unqualified vehicles use the new lane, and there is no mode shift.)