r+d

Interesting concept by Damjan Stankovic, a Serbian designer/innovator. While Damjan lists several green attributes to the light, I'm more sold on the one that deals with stress. One of the fundamental tenets of good usability and user experience is providing the user with an awareness of a system's status. Doing so allows the user to set expectations for system behavior and plan for their next actions. This light accomplishes this sharing of system status information in a very elegant way.

From the site:

Eko light is a simple yet, highly practical concept for traffic lights that not only helps preserve the environment by reducing pollution but promotes safer driving as well. Eko can be easily installed onto existing traffic light systems without much effort while significantly improving overall traffic dynamics. There are many benefits of the Eko light, the main ones being:

Less pollution. Drivers can turn their engines off and cut carbon emissions while waiting for the green light. Turning off your vehicle while waiting on the traffic light can lower fuel consumption in the long run.

Less stress

Since you know exactly how long you have to wait you can sit back and clear your head for a while. No need to keep your foot on the gas. Relax.

Safer driving

With the Eko light both drivers and pedestrians can be fully aware of how much time they have left before the light changes and that way reduce the chance for potential traffic accidents.

In any case, I think it's a great concept that's accompanied by several other interesting concepts on Damjan's Relogik site.