We talked earlier about Smart Cities and benefits of traffic signal timing study and optimization. Kindly read the following link for a more detailed explanation of conducted studies.
Next is a link to RITA , Research and Innovative Technology Adminstration, Intelligent Transportation Systems. Quoting from their summary information below as a low hanging fruit strategy for Smart Cities
Optimizing traffic signal timing is considered a low-cost, high-benefit approach to reducing congestion. Signal timing strategies include the minimization of stops, delays, fuel consumption and air pollution emissions and the maximization of the traffic progression through the system.
Looks like it does not take much to make Smart Cities