Montana is a state that feels like a country. It takes 10 hours to drive across it east to west, and six heading from the south towards Canada. Its licence plates say Big Sky Country, but they wouldn't be lying if they said Biggest Ever Sky Country.
This is the kind of place that is made for the road movie and even more so since it became the only state in America without a stated speed limit. Surrounded by panoramic horizons and faced with a long, straight and empty road, it's tempting to believe Thelma and Louise are alive, well and driving your car.
They do drive fast. And why not? For 21 years, all Americans had to put up with a federal speed limit of 55 and then 65mph. Last December, Washington finally scrapped this "conservation rule" and left it up to each state to set its own limit.
Most set 70mph for interstate highways and 60mph for state two-lanes. But Montana is not the home of the Freeman militia for nothing.
So welcome to Basic Rule country. This says you have to drive in a "reasonable and careful manner", taking account of traffic, weather, road conditions and the state of your car. In other words, rely on common sense, not your speedometer, to stay out of trouble. This is self-regulation for Everyman.
Lieutenant Janet Baker, of Billings Highway Patrol, is not sure. "The concept is good but reality is a little confusing for some. It becomes a matter of my opinion versus theirs. Often people don't think they are doing anything wrong at 95mph."
But all opinions are not equal on the verge and since Montana scrapped its declared speed limit the number of tickets issued has doubled . So self-regulation has been a big success in one area: it has raised lots of extra cash. Spot fines range from $70 to $500 (pounds 45-pounds 325).
It has also led to an increase in what Major Steve Barry of Helena highway patrol calls "official-violator relationships". These turn out to be those unpleasant, roadside affairs we have all vowed to avoid.
Major Barry gets lot of letters requesting that Montana quit all this commonsense stuff and adopt a normal speed limit. If you go by the current actual average speed, that would be 74mph (up from 72mph under the old, 65mph speed limit).
But there is sense and nonsense. Take the motorist who was stopped last week in Big Horn County for driving at 130mph. "That's just insane," says Lt Baker. But it's not, really - if Thelma and Louise are chasing you.
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