I have been driving a car with stop start technology for over 2 years in the UK. I find it utterly unobtrosive. I wonder whether this is because, like the vast majority of cars in the UK, it is manual and so I am in control (the engine only stops when I put it in neutral). Surely one of those letters next to the gear stick in an automatic is the equivalent of neutral? If so, shouldn't the engine only stop when you put the stick next to whatever letter that is? (I have never driven an automatic, so am rather ignorant on the subject)
However, given automatics use more fuel, if you want to save fuel, wouldn't it be more sensible to switch to a manual (with or without stop start technology)?
I have been driving a Honda Insight which has this technology for a couple of years now. The delay from the start is practically not an issue. By the time that I have finished releasing the brake the engine is started. The lack of AC is annoying, particularly for my wife. I tend to not think about it much unless it is a hot day, and even then it doesn't bother me that much. The engine kicks back on if I have been sitting for very long, and if the car has been running for a while the heatup isn't as quick. One advantage here in SoCAL is that practically all of the lights have sensors, so long light waits are really not all that common. I sometimes find myself wishing for a longer light when I want to reach for something in the car!
I would not be nearly as concerned about off-the-line performance as I would be about the need for continuous operation of the A/C. If you live in a climate where the interior temp of the car immediately starts rising the moment the A/C shuts off, then the prospect of sitting through a red light cycle without A/C will prove to be very unpopular.
I really think you're making too much of the time to restart. In the Mercedes system with an automated transmission, the engine only shuts off when you have your foot on the brake. The engine restarts autoamtically as you move your foot front brake to accelerator and it's delviering power pretty much as soon as you get to the gas pedal so there's no more risk of being caught out by speeding motorists than with a conventional transmission.
I like the thought of a vehicle that makes the possibility of saving fuel at red lights more convenient.
I just think the implementation is bad. I don't think it should be based on whether or not the vehicle has come to a complete stop. This has safety implications because as another reader pointed out, there are times where you may be at a stop sign where you likely will want to proceed at any random time, and at that, promptly. My own neighborhood has but three exits and the closest one of them meets a heavily travelled two-lane each-way undivided highway with no traffic light. There is also a nearby hill causing reduced visibility of traffic approaching from the right, and the lead cars in each group of traffic departing from the traffic light 1/2 mile away in that direction are typically speeders. In this and many other conceivable situation, an extra 0.3 seconds delay in resuming travel after every stopped state would be unacceptable.
However, these days, we could consider more sophisticated instrumentation for whether or not such a stop would be appropriate. How about a directional low-intensity RF, microwave, infrared or possible even visible, signal that could be issued to only the cars in the lanes that are being stopped by red lights? The signal would mean "All engine computers modern enough to understand this signal, please stop your engines now" engine-off behavior. Such a signal could be removed or terminated max-actual-engine-start-up-delay seconds prior to the light changing to green. This way emergency vehicles could terminate the signal early when they want people's engines on so that they can contribute to clearing a path. There should also be an over-ride in the car itself.
I've no idea about the claimed times but from personal experience with rental cars in Europe and now a recently acquired Mercedes CLA it's so slight as to be a non-issue - my Father-in-Law hadn't even realised the card Mercedes was actually shutting off at lights until we pointed out the rev counter was at zero!
I don't understand why this isn't standard in more cars.