Improving how traffic lights work to create green waves on as many streets as possible not just the 1 ways. This will reduce traffic, accidents and CO2 emmisions and increase transit performance with fewer vehicles grid lock idling.

Anyone who's sat at a red light for minutes on end in the middle of the night when there's no cross traffic can cheer on science for proving what we already knew: lights that adapt to the flow of traffic, instead of dictating the flow of traffic, can improve the flow of traffic. A team of researchers discovered that if you let lights locally decide how to time their signals based on how much traffic they're dealing with, and then communicate that with nearby lights, you get closer to the "green wave" of lights that keeps thing moving smoothly.

The issue with the centralized, top-down system of control is that it is geared to address an average traffic situation that rarely occurs as planned. The variations in rush hour traffic mean that lights are trying to apply one solution to a vast number of situations. In their trial in Dresden, Germany the team found that traffic congestion was eased by nine percent, pedestrian congestion by 36 percent, and bus and tram traffic by 56 percent. With rush hours spreading in time and distance, the proof and implementation of this can't come soon enough.

http://www.autoblog.com/2010/09/23/study-traffic-lights-should-respond-to-cars-not-other-way-arou/