Let's face it, for most police cruisers it's a hurry up and wait kind of existence. A study by the police in Ottawa, Canada found that most cruisers sit with the engine idling for about 6.7 hours out of every 10-hour shift. The problem is that modern police vehicles are crammed with gear like radios and computers and also need working climate control systems. As a result, it simply isn't practical to shut them off all the time because they need power. Of course, more of the time, the cops also don't need the full power of a running V8.
The Ottawa police installed anti-idling technology in two patrol cars for a year-long test and found that fuel consumption was reduced by more than 10 percent. These weren't just basic start stop systems like those found on many European cars. The $2,000 system includes auto-shut-off for the main engine, extra batteries to operate the electronics and a small engine for heat and charging. Considering the low mileage that operational cruisers are likely getting, the 10 percent savings adds up to a pretty significant chunk and the payback takes only 18 months.
[Source: Ottawa Citizen]