One source of inaccuracy in the traffic simulation of Section C 9.5.4 has to do with the timing at traffic signals. If a signal is currently green in the EW direction, but the queue of waiting cars is empty, the signal coroutine will go to sleep until current_time + EW_duration. If a car arrives before the coroutine wakes up again, it will needlessly wait. Discuss how you might remedy this problem.