The idea that it takes more gas to start a car than to leave it on is not valid if the car is idealing fro more than 10 seconds. A magorety of our car's stops are much longer and it is energy saving, money saving, less puloting to turn off the car when Ideal.
Of course this needs to be done when its possible and safe But it is also possible to do at a red light when you know its a long one and reignite before it turns green.