Traffic Management Traffic lights are key tools for regulating traffic How.They are not, however, perfect.Drivers exchange the traffic jams that would happen at unmanaged crossings for a pattern of stop-go movement that can still be annoying, and which bums more fuel than a smooth passage would. Creating such a smooth passage means adjusting a vehicle's speed so that it always arrives at the lights when they are green.That is theoretically possible, but practically hard.Roadside signs wired to traffic lights can help get the message across a couple hundred metres from a crossing, but such signs are expensive, and are not widespread.Margaret Martonosi and Emmanouil Koukoumidis at Princeton University, and Li-Shiuan Peh at the Massachusetts Institute of Technology, however, have an idea that could make the process cheaper and more effective.Instead of a hardwired network of signs, they propose to use mobile-phone applications. For a driver to benefit, lie must load the team's software , named SignalGuru, into his phone and then put it on a special thing attached to the inside of his car's windscreen, with the camera lens pointing forward.SignalGuru is designed to detect traffic lights and track their status as red, yellow or green.It broadcasts this information to other phones in the area that are fitted with the same software, and --if there are enough of them ?the phones thus each know the status of most of the lights around town.Using this information, SignalGuru is able to calculate the traffic-light schedule for the area and suggest the speed at which a driver should travel in order to avoid red lights. Tests in Cambridge, Massachusetts, where five drivers were asked to follow the same route for three hours, and in Singapore, where eight drivers were asked to follow one of two routes for 30 minutes, revealed that SignalGuru was capable of predicting traffic-light activity with an accuracy of 98.2% and 96.3% respectively, in the two cities.This was particularly impressive because in Cambridge the lights... Roadside signs wired to traffic lights are not the best way to create a smooth passage because _ . A) they are expensive and easily break B) they are too costly and not widely used C) they are complex and confusing to drivers D) they are theoretically possible but practically useless
The answer to this question is:
B