very nice example of bicycle,helps in getting the idea.
also turn off enginge instead of idling at redlights.
but never ever ever turn off engine while the car is running.
it has two major dangers.
1.You might turn over the key to steering lock position and steering will lock in an event of emergengy maneuver.
2.while the engine is turned off,the break system of some cars does not work on full potential.(to chek this,let the car glide on a slight slope At NEAR ZERO SPEED and apply brakes 2,3 times,and feel the difference of brake grip.the break loosens due to hydraulic system not working and its only foot pressure that works.
my gli 2010 is equipped with brake assist.it happens like this and its also mentioned in the manual.
please share the result of other cars.