It's a fledgling market for now, but it won't be long before a majority of new vehicles will be available with rear-sensing systems to help drivers squeeze into tight spaces when parallel parking.

After its introduction on European luxury cars in the early 1990s, the product arrives in the U.S. in time to capitalize on a market that loves big sport/utility vehicles that offer inadequate rear vision to prevent backing over garbage cans, tricycles or, worse yet, small children.

The solution is ultrasonic (and next-generation radar) sensing systems to detect these objects and to alert drivers with a series of obnoxious (but effective) beeps. The closer the vehicle gets to the object, the more intense the beeping.

When the object is within 10 to 20 ins. (25 to 50 cm), the sound becomes a constant tone.

Valeo SA of France is a top supplier of rear-sensing systems after its September 1998 acquisition of the electrical systems business of ITT Automotive for $1.7 billion.

The "Park Assist" package must have been one of the plums in the deal for Valeo, as ITT had already landed some significant North American contracts for the system.

At the time of the purchase, Ford Motor Co. was rolling out its new Windstar minivan, a vehicle marketed for its safety features, equipped with optional Park Assist. Midway through the 1999 model year, Ford's Explorer and Mercury Mountaineer also offered it.

And now for 2000, Lincoln Navigator, Ford Expedition and the gargantuan Excursion all are available with it.

Ford's commitment to the technology gives Valeo the lion's share of the market for rear sensing in North America now, but that could change relatively soon.

Robert Bosch GmbH supplies the ultrasonic Rear Parking Assist as an option on the Cadillac Seville STS and SLS and on the 2000 DeVille, and it will launch similar systems on several other General Motors Corp. platforms over the next two years.

Within five years, Bosch estimates its North American market share in rear sensing will be about 60%. Valeo estimates that the number of sensing systems on new vehicles in North America from all sources will blossom from 200,000 units in 1999 to 1.1 million in 2003.

Bosch and Valeo already are the top suppliers for the technology in Europe, where the predominance of parallel parking and tight spaces created the ideal market for launching rear sensing several years ago. Bosch is the sole supplier for Mercedes-Benz, which offers it on everything from A-Class to S-Class in Europe.

Ultrasonic is the predominant principle applied to rear sensing today, but radar, despite costing twice as much, has been tagged as an ideal technology for the future. Radar offers increased range (20 ft. [6.1 m], compared to 6 ft. [1.8 m] for ultrasonic).

Plus, up to six ultrasonic sensors used today can be replaced with two radar sensors. From a packaging standpoint, radar sensors can be hidden inside a bumper fascia, eliminating the unsightly black dots that adorn, for instance, the Windstar's back end.

Which technology wins out remains to be seen, but sources at Bosch and Delphi Automotive Systems say a hybrid is soon to appear that uses both ultrasonic and radar. Bosch and Delphi both are pursuing radar aggressively, while Valeo is attempting to extend the range of its ultrasonic system to 16 ft. (4.9 m), making it competitive with radar.

Another wrinkle in the market comes from Ford. Despite its current commitment to Valeo in ultrasonic, the No. 2 automaker is now working with Delphi's Delco Electronics division on next-generationradar systems. Delphi has other customers and will have its Back Up Aid system in production within two years.

Bosch and Delphi officials say radar's extended range gives it a big advantage in the U.S., where people backing down long driveways need advanced notice of an obstacle if they are to stop in time.

As for current systems, one metro Detroit Ford dealer says buyers like the feature, but not the price. On Windstar, the optional retail price for reverse sensing is $245.

"We have 50 to 60 Windstars in stock right now, and none of them have it," says a salesman, who asked not to be identified. "When you add these things, people like them, but they don't want to pay. If it were standard, they'd love it."