The roads are narrow, often single-lane. They wind through agricultural fields and industrial plateaus into the small towns and villages of northwestern Germany.

You must slow down in those places. The residents are unaccustomed to cars as fast as the 2005 Porsche 911 Carrera, or its even faster sibling, the 911 Carrera S. Little children walk and run across streets unattended. Some senior citizens amble along the sides of roads. And there are the occasional commuters on bicycles. Driving fast in such a milieu is both dangerous and impolite.

There will be time and room enough to speed, really speed, on those long stretches of autobahn uncovered by limits of any sort. That is where Porsche becomes Porsche, where the new 911 cars, the sixth generation of their breed, come into their glory.

Consider the "base" 911 Carrera. It comes with a 3.6-liter, horizontally opposed six-cylinder engine that develops 325 horsepower at 6,800 revolutions per minute. Torque, the twisting power exerted on the drive shaft, is tremendous at 273 foot-pounds at 4,250 revolutions per minute.

To handle that power, Porsche developed a new six-speed manual gearbox employing larger-diameter shafts and wider gears, which means more weight for those components. But the weight gain is offset by the use of strong, lightweight parts elsewhere in the transmission.

The result is a manual gearbox that moves effortlessly through changing speeds in short, precise shifts. Driving becomes choreography under the circumstance. Driving at autobahn speeds in the 911, at the U.S. equivalent of 120 miles per hour in one case, is akin to dancing salsa or tango.

Porsche's five-speed Tiptronic S transmission, an automatic gearbox that also can be operated manually, is available as an option. There is magic in that one. It moves deftly to fifth gear at high speeds; and it falls just as quickly and smoothly into the lower gears upon deceleration. There is not the least bit of hesitation in the Tiptronic S's gear transitions.

It is seductive. The base 911 Carrera and the bigger-engine, 355-horsepower Carrera S run so well, they are a blessing and a curse. It is easy to break the law in these cars. Your smile can quickly turn to chagrin if you aren't paying attention to what you are doing and where you are when your foot is pressed to the gas pedal.

For example, Germany's autobahn isn't totally free of speed limits. As is the case in the United States, drivers must slow down on highways approaching or bypassing cities.

Swirling blue lights atop little green cars give ample evidence that the German police are up to the task of arresting speeders in limit-governed zones. And what the police miss, multi-positioned autobahn cameras catch, electronically nabbing and penalizing offenders. It is a very efficient traffic control system.

I enjoyed my Porsche romp ticket-free. Chalk it up to timidity. Even at 120 miles per hour, I had to yield the left lane on the limit-free portions of the autobahn to faster drivers. Surely, I could have stayed there in either the base 911 Carrera or the Carrera S. Both cars are equipped with electronically controlled stability-management systems that keep them perfectly balanced at super-high speeds.

On the Carrera S, large, sticky 19-inch-diameter tires -- the biggest ever put on that car -- help guarantee traction around curves and in rapid lane-change maneuvers.

But the laws of physics are immutable. At some point, it is possible to violate them with tragic results, even in a Porsche 911.

Rain fell. Road spray rose. Forward vision declined. But the left lane continued to hum along at terrific speeds. I moved to the middle lane. Trucks dominated the right lane, staying where all big trucks belong, giving up the middle and left lanes to faster traffic. I slowed down to a more comfortable speed of 95 miles per hour.

What a country! What excellent lane discipline! What a wonderful automotive duo -- the base Carrera and Carrera S! Driving safely at 95 miles per hour, and doing it all quite legally, in the rain! It was the last leg of a long day behind the wheels of the two cars. I was finishing up in the Carrera S, elated, thrilled. But my mood became clouded by the saddest of realizations: These cars, though they'll find their most lucrative market on my native shores, are far too competent for many of the highways and laws we have -- and the way we drive in the United States.

Back home, a simple Volkswagen Jetta would make more sense.