ABI Research has a study on Belt-Alternator-Starter ("BAS") cars, an urbanite's cheap alternative to hybrids. They basically are a normal car with a bigger alternator/starter combo, and automatic engine shutoff, to avoid engine idling. ABI charges to download the paper, but have a press release that roughly describes their findings:
"The devices allow for start-stop operation similar to hybrids, where the engine can be shut off at a stoplight or when idling, but at a price premium of just a few hundred dollars instead of the thousands required for hybrids. However, ABI Research cautions both consumers and financial observers that, 'you get what you pay for... A BAS doesn't provide any sort of assist in actually propelling the vehicle, and will often have far less capability for regenerative braking, if any.' "
Still, people stuck in stop-and-go traffic for most of their driving could see significant increases in mileage. And since these driving conditions make for the worst inefficiencies, they are a good first target to tackle. Besides that, efficiency shouldn't be limited to those who have the money for a fancy new Prius. It will be interesting to keep an eye on this technology in the upcoming years.
