Australian traffic signals are also 'smart'. They don't cycle in non-peak hours. They just use sensors to detect oncoming traffic and route appropriately. Main roads default to green, but lights on side roads will switch just before you drive up to them.

This is why the buttons are necessary during non-peak hours... If I press the button, the light will go red as soon as it's safe. Jaywalking isn't a crime here, but this is still very useful in some situations.

Our "Coordinated Adaptive Traffic Control" systems are pretty awesome. Even during peak traffic, all the lights are controlled by a central control room, with a computer that manages all traffic flow as efficiently as possible. It will sometimes shut down a lane or modify a speed limit to allow emergency traffic through or prevent grid-lock further down the freeway, reducing overall travel time. It's able to simulate different traffic flow models and select the best one. The result is that even during peak hours, I can easily travel from the outer suburbs to the CBD (30k/20mi) in approx 40 minutes.

Details here: http://www.scats.com.au/