As congestion builds on one street relative to another, it adjusts traffic-light cycles to give more green time to the congested lanes.

FORBES: Photograph: Tim Rue

When a GPS-equipped bus approaches an intersection, it can, as before, take over the intersection's traffic light, but the computer can also calculate its expected time of arrival and decide either to extend a green light or shorten a red light.

FORBES: Greening the Traffic Lights

At about 2145 BST, eyewitnesses reported seeing the sky light up with green flashes at the same time as the four explosions, which were thought to be stun grenades.

BBC: Probe held into armed siege death

This time, Iraqi and American forces will have a green light to enter those neighborhoods.

FORBES: Unhealthy

It is an interesting triple "coincidence, " which probably evolved over time, that our eyes are most sensitive to yellow-green light, which happens to be the characteristic color of sunlight as well as the color that can most easily be transmitted through the Earth's atmosphere.

CNN: Why gamma-ray burst shocked scientists

Supporters of the scheme say a decision is needed this year, but it was clear at question time that ministers are a long way from a position where the scheme will get the green light.

BBC: Severn Barrage debate takes off in Lords