I'd rather prefer EVs or even Hybrids for stop start feature to work well. They already have start-stop features builtin.
I wouldn't care for the stop start on a gasoline car without hybrid, but rather consider safety and comfort features instead. I guess the total savings in gas will be insignificant unless the stop time is huge... in which case most of the drivers turn off the engine when not needed, or would like the engine to be on for comfort.
I wouldn't worry about the need to leave the engine on when defrost or air conditioning is needed. Determining if the engine should remain running based on environmental parameters would be an easy taskwith the amount of computing power available in todays cars.
As for the delay in restart, that's really only an issue for the first one or two cars in line at the intersection. Add a wireless transmitter to the traffic signal and cars could automatically re-start a second or two before ther light changes.
Where gasoline is very expensive, like Europe, it was not unheard of that people turned off their engines at red lights. Whether or not their vehicle was "start-stop."
One thing you didn't explain, Junko, is how you keep the heater or air conditioner running, when the engine is off. In practice, many/most/all(?) hybrids do not stop the engine if you are running either heat or air. Try it on any car. Turn off the engine at a stoplight, either during cold weather, or while it's raining and the windshield is fogging up, or on a hot summer day. With the interior fan running just on battery power, see well this works. Not very well! The heater core cools down very quickly when the (mechanical) water pump isn't running, and the blowing air warms up very quickly when the (mechanically driven) air compressor isn't running. I haven't seen either electric water pumps or heat pumps used in regular or hybrid cars just yet! I'm not sure how safe an electric water pump would be, for that matter. (Possibly, it could be designed to run on battery power only if the car is stopped, but that would put a heavy load on that battery.)
These days of computer-controlled machinery, this all can be made intelligent enough. But then, what this really means is that often, the engine won't turn off. Or if it does, not for long.
I drive a Prius (in Europe) and as you say the delay isn't really an issue with a hybrid. There is though a noticeable change of torque as the ICE kicks in and this can be annoying if it happens while cornering but you get used to it.
There are still quite a few cars around with manual transmissions here and they can take forever to pull away, sometimes so long that the traffic lights change before cars behind get through (lights can have quite short cycles here). Fuel is so expensive that people don't want to waste it on an automatic transmission. So stop/start might actually be faster as well as cheaper in that situation.
Start&stop tech is no news in Europe at least, marketed with different names by all the vendors. I personally own a Volkswagen Tiugan, diesel, year 2011, which uses the same tech marketed as "bluemotion". All I can say is it works painlessly, engine shuts down exactly when I want, restarts quickly, saves quite some fuel when transit stops - but make sure you do not use it for short stops, might not save fuel at all, but the opposite. From my experience, a 2-3 minute or more stop is worth using S&S, less than this does not.
In fact, as I wrote in the story (page 2), hybrid/electric assist vehicles experience almost no delay in power from a stop, due to the instant availability of power from the traction battery to the electric motors.
The issue is when we try to do this on our non-hybrids.
Non-hybrids must rely on a run-of-the-mill starter motor, which is usually too weak for a seamless reboot. That results in that slight partial-second delay in gasoline cars. One solution is to increase the size of the starter motor. But this would add weight and cost.
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