There are many new cars now that automatically turn off their engines when stopped at traffic lights. They then automatically turn them on when moving off. These systems have many names along the lines of active or eco .
The manufacturers claim that these systems are to save fuel, reduce running costs and save polar bears. At the same time there are no published figures detailing the economies involved. Is this just marketing hyperbole? It seems to me that switching your engine off when it's at a warmed up idle is absolutely the last place that would generate any fuel saving worth printing. Most cars idle at ~ 0.3 gallons per hour anyway which is nil in the context of a typical trip. These systems also require a larger alternator, battery, and starter motor. It's a con init?