I've tested City Safety, and it works as advertised: Under 10 miles per hour, the car stops fine, and with only minor nose-dive. Over 10 mph, where Volvo says it might work but at least it will "mitigate" a collision, City Safety came through like a champ as well. At higher speeds, the braking can be severe and sudden. But what's a spilled cup of coffee versus clipping a pedestrian or the back of another car? Priceless. And that's why Volvo City Safety is our 2010 Digital Drive Technology of the Year.

Runner Up (tie): BMW Assist's Enhanced Advanced Crash Notification

A car hits something solid, the airbags go off, the car's "mayday" calling system automatically seeks help. No matter how severe the crash, financially strapped responders typically send a policeman to evaluate the accident, and only afterward call for an ambulance or medical evacuation helicopter. For the past two years, BMW has worked with the University of Miami/Jackson Medical Center's William Lehman Injury Research Center to develop "urgency risk of severe injury" algorithms that predict which crashes may be so severe as to require dispatch of an ambulance right now. This is what's called Enhanced Advanced Crash Notification. The BMW Assist (telematics) call center has the capability now to receive information on the condition of the accident and the likelihood of occupant injury.

The trick is getting the federal Center for Disease Control (which includes auto accidents) to tell the country's 911 call centers, called PSAPs (public safety answering points), that the information is good enough to stake your life on. If CDC orders it, the PSAPs would go along. BMW is working on persuading CDC; CDC wants more data points. So BMW freely licensed the techniques to GM and its OnStar system,because it's not uncommon for automakers to share lifesaving technologies, and also because between the two, they'll get more convincing results sooner as researchers compare what the eACN algorithms predicted versus what the EMTs and hospitals found. (GM has 4 million OnStar cars on the road.)

One example of a life-saving situatino: A severe side impact might cause tears in the aorta, yet the victim might feel okay and look fine to EMTs--right up until he exsanguinates. But the EACN report would suggest he or she belongs in the hospital pronto.

The payoff is still a couple years down the road for the thousands of lives saved that BMW talks about. But for the increasing number of cars with mayday calling, this could be a new formula for safety.

Runner Up (tie): Ford 911 Assist with Ford SYNC

It's hard to beat free. That's the road Ford takes with 911 Assist, a mayday calling service that requires the driver to help out.

911 Assist works through the Sync Bluetooth handsfree service installed on most Fords, Lincolns, and Mercurys within the last two years (our Technology of the Year last year.) If the driver has his or her Bluetooth cellphone connected and in a safe spot where it won't be jolted by an accident (a clothing side pocket or the closed console, perhaps), 911 Assist calls for help in an accident, just like the $15-a-month mayday calling services. At no charge, using the driver's cellphone. 

Critics note embedded phones such as OnStar's survive virtually every crash and have better antennas. Critics of the critics will note that the renewal rate for OnStar and its kin is believed to be less than 50 percent after the initial provided service, usually one year, meaning the success rate for an OnStar-type system would then be, at best, 50 percent. Ford's next step to increase the security of 911 Assist should be to provide a padded, adjustable-size cradle in the center console, plus a power outlet, so the phone survives virtually every accident. 

911 Assist is paired with Vehicle Health Report, which passes along, again via Sync and your phone, information on your car's operation condition such as the condition of the engine oil and diagnostic codes. Also free.