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It’s not often that after testing a car, this question lingers: ”What did I just drive?”

This Mercedes-Benz seats six in individual bucket seats stacked in three rows — a modern crossover. It has all the glass and panoramic side views of a minivan, the utility and permanent all-wheel drive of an SUV, and the ride of a luxurious station wagon. Electronics are used to keep this wholly new 2006 R-Class transporter down to 130 miles per hour, yet it turns into a hauler of prodigious cargo, and has a glass roof that stretches overhead like a cathedral ceiling.

It would be easy to say this is one of the new and popular ”crossover” vehicles — part wagon, part minivan, part SUV designed to eliminate the worst traits and reputation of each while preserving their best characteristics. It’s not.

But it is a car that has crossed over — albeit at a hefty price tag — to where nothing like it has yet gone.

It is no Chrysler Pacifica — a similar and popular car from DaimlerChrysler to which it will be compared. It’s certainly not an SUV, though its AWD, adjustable suspension, and ride control will get you through deep snow or over rough spring roads.

Let’s just say we’re driving the future, and though this particular future — R350 or R500 — is beyond the means of most ($50,000 to $70,000-plus), many of its elements will be copied for less.

It is powered by either a 268-horsepower V-6 engine or a 302-horsepower V-8 (as tested). Both are mated to seven-speed automatic transmissions that can be shifted using buttons mounted on the back of the steering wheel.

Power is distributed 50-50, front and rear under normal driving. It can, however, be sent in either direction or even to one wheel, if that is the only wheel with purchase. Add stability control, ABS, and traction control and you have an almost idiot-proof hauler of six people.

Those occupants ride in the variable embrace of air suspension with three settings: normal, comfort, and sport.

Normal is benign and good for cruising. Comfort softens the ride and, while it makes it a bit tippier in corners, absorbs bumps. Sport stiffens the ride, holds it upright in corners, reveals bumps with a bit more thump, and is perfect if you’re going to drive aggressively.

Considering the weight, the ride is smoothed by supple handling, aided by a 126.6-inch wheelbase.

Seating is high, providing sweeping views over the low cowl and out the vast greenhouse of side windows. And the seating is oh-so-firm, with full-blown bolstered buckets at every position, and adjustable in many ways. For instance, the center row slides back and forth 6 inches, allowing generous leg space. If you don’t need the center or rear seats, they all fold flat, offering what is billed as 85 cubic feet of cargo space — more than in many big SUVs.

Ergonomics are typically Mercedes-Benz functional and intuitive, though the smallish buttons that run down each side of the center control screen take some getting used to.

The base price on the test car was $55,500, which included such basics as the bigger engine, four-wheel traction control, 18-inch, five-spoke wheels, eight-way power front bucket seats, dual-zone climate control, side curtain air bags at all seats, and privacy glass.

An upgraded entertainment package, heated seats, panoramic roof, air suspension system, Sirius satellite radio, iPod integration kit, and parking sensors, among other goodies, had us $10,000 over that. And yes, you can go higher, topping $70,000.

Confused sometimes with the Pacifica? Yes. But that’s like comparing a Mazda Miata to a Porsche 911.

Not that there’s anything wrong with either. Some vehicles just travel a different road; some into the future.