CHANDLER, Ariz. -- The West Test Track at Firebird International Raceway in the Phoenix suburb of Chandler is clear of traffic except for two vehicles -- a lead car and the chase car.
Lead vehicle is the ML500 SUV from Mercedes-Benz and it's setting a swift pace ahead of the chase car we're steering.
Ours is a full-size super-luxury S Class Mercedes sedan which scores a generational change for 2007 and emerges with a new powertrain and nameplate as the S550.
We think the S550 is one of the most intelligent cars in the world.
How "smart" is it?
Well, this car shows us it can actually out-think a driver at times and make intelligent decisions regarding vehicle speed, movement and safe operation.
For instance, the radar-based cruise control system aboard our S550 chase car is capable of maintaining a precise distance between the S550's front bumper and the back bumper of the ML500 lead vehicle directly ahead.
And if the vehicle in front should slow down and stop, the S550 also slows and stops -- without the driver ever touching the brake pedal.
That's what we experience on the Firebird track: When the ML500 scoots along at 70 mph, the S550 follows, leaving a space of about five car lengths (the distance we select from a tab on the steering wheel) between lead car and chase car.
But when the SUV hits the brakes and slows to a stand-still stop, the S550 does the same.
And when the ML rolls forward again, the S550 moves again too, as if an on-board ghost driver is working both brake and accelerator pedals.
New S550 comes with many more "intelligent" devices.
One is called Pre-Safe.
This automatic tool, also drawing on radar imagery, instantly rigs the vehicle for an unavoidable impact.
It activates electric seat belt tensioners and aligns the passenger's front seat in ideal position with backrest raised, seat bottom lowered and the seat shoved rearward.
Side glass closes for better support of curtain-style air bags tucked above side windows, and if sensors detect an impending rollover event, the sunroof zips shut too.
There's even a radar-based parking tool.
Dubbed Park Assist, the optional system relies on six unseen radar sensors mounted behind front and rear bumpers plus camera images projected on a dashboard screen of the navigation system with color-keyed outline overlays applied to indicate optimum and actual projected paths of the vehicle when executing maneuvers to park parallel.
And in nighttime darkness another smart device called Night View Assist uses invisible infra-red light from dual projector beams mounted in headlamp clusters to create a black-and-white video display in the instrument cluster. The reflected images on the video screen clearly show far more than the naked eye can see for 500 feet on the path ahead.
The 2007 S550 looks bold and rather angular in body style and it seems quite large.
Actually, the only version shipping to North America is the stretched edition riding on a long-wheelbase platform which measures about three inches longer in wheelbase than the previous generation of S Class cars.
The package size expands by 1.7 inches in length and almost an inch in width, and these added dimensions translate to more space in a luxurious passenger compartment filled with comfortable features.
Surprisingly quick for a triple-ton big car, new S550 packs a new dual-cam V8 engine which displaces 5.5 liters to explain the 550 nomenclature of the nameplate.
The aluminum plant generates 382 hp at 6000 rpm and peaks the torque at 391 lb-ft across a board band from 2800 to 4000 rpm.
That's enough muscle to propel the S550 from a stoplight start to 60 mph in a couple of ticks over five seconds.
Transmission is the impressive Mercedes 7G-tronic TouchShift automatic -- a seven-speed automatic transmission employed in many different Mercedes models.
The 7G-tronic operates with a stubby stalk protruding from the right side of the steering column. To select a gear, you raise the stalk one notch for reverse, lower it one click down for drive or depress a button on the stalk's cap to park.
While driving, you may leave the stalk in full automatic mode or play the TouchShift buttons -- positioned on the back side of the steering wheel's cross bar -- to switch gears. To-and-fro movements of the TouchShift buttons step up or down the gear ladder one notch at a time with the control of a manual stick.
There are multiple devices aboard the S550 to stabilize all forward movement and tire traction.
Sensors in the suspension system determine vehicular payload, speed and road conditions, and they can adjust dampers on shock absorbers to smooth out or firm up the ride quality. Still other devices measure wheel speed and lateral acceleration and can brake an individual wheel to correct potential skidding or spinning of the car.
Also on tap is the alphabet soup of computerized vehicle controls -- anti-lock brake system (ABS) with brake assist plus (BAP) and electronic stability control (ESP).
And Mercedes provides roll-over sensors, curtain-style air bags for both rows of seats, and a tire pressure monitoring system (TPMS).
The elegant cockpit is swaddled in soft leather hides and decorated with exotic hardwoods and bright chrome trim.
Layout consists of a pair of bucket seats up front with 16 ways of adjustments and active pneumatic seat supports. In back there's a bench for three or two articulated buckets with reclining seatbacks.
The dashboard features a swoopy strip of wood defining two front seat spaces with arching brows over the driver-side instrument cluster and center-spot navigation screen.
At hand on the console is a rotary mouse for the Comand system which accesses many vehicle controls.
Mercedes sets the MSRP for a "smart" S550 of 2007 at $85,400, which tallies to a few hundred dollars below the MSRP of the predecessor S500.