I think I read somewhere that the cut-off point at which it makes sense to shut the motor off while stopped is something like 15 seconds.
That is, if you will be stopped longer than 15 seconds it makes sense to shut off your motor and restart.

I'm sure the hyper-miler forums are full of such information.

I've also heard that a good portion of the mpg gains that the hybrid cars provide is due to good aerodynamics.

As for the traffic signals using yellow before green- it's obviously a plot by the manufacturers of yellow lights to get more hours on the ones in service so they'll be replaced more often.