The best start-stop automotive system is a small hybrid system that does nothing more than roll the vehicle the first five to ten feet from a stop. Of course the internal-combustion-engine starts up during that roll.
But current hybrid systems are larger, heavier, and more expensive than just a system for beginning a roll from a stop.
Now the best hybrid is the BMW i8 because it uses the hybrid system to make an overall four-wheel-drive. However, even that car can be used for a short range in an all-electric mode such that after the sort range then the hybrid system is no longer available for assisting the internal-combustion-engine.
These larger hybrid systems work best as assisting the internal-combustion-engine such that there is then less load on the internal-combustion-engine. However, these hybrid systems are very large so as to have a short all-electric range which of course quickly depletes the hybrid system. Also, the weight and cost is too much with the larger hybrid systems.
The car I recommend for the average driver is a rear-wheel-drive sedan or coupe with a 2.0 turbocharged engine and no hybrid system. The turbocharged engine makes good torque which is a feeling that most drivers like. Also, the peak torque is at low RPM which helps city driving and improves city MPG. Just watch out for vehicle weight even here.
Well, the cities could limit non-commercial vehicles to 2.0 engine size during business hours and could limit commercial vehicles to 3.0 engine size during business hours. The quickest and easiest way to reduce vehicle pollution would be for the cities to pass laws.