The Associated Press reported this week on the repercussions at TomTom, a leading maker of personal GPS devices, after it emerged that police in the Netherlands had been setting up speed traps based on data purchased from the company. It's not surprising that TomTom would be selling its data to generate more revenues; ever-improving smartphones are killing the market for GPS devices. Nor is it surprising that Dutch police departments would be setting up more speed traps; governments in many countries are desperate for revenues amid a weak global economy, so the temptation to write more traffic tickets has to be strong.

But setting up speed traps is exactly the wrong response to GPS data identifying areas where lots of people are driving faster than posted limits. Indeed, those same data likely indicate precisely where speed limits ought to go up.

There's a science to speed limits. Traffic engineers assume that, a few crazy leadfoots aside, most drivers are good judges of how fast they can safely travel. As this Massachusetts guide puts it:

The speed at or below which 85 percent of the motorists travel is the principal value used for establishing speed controls. This is commonly referred to as the 85th percentile speed. This method is based on numerous studies which indicate that the majority of motorists are prudent and capable of selecting safe speeds. The 85th percentile speed is the national standard for establishing safe speed limits.

If you scroll down in the Massachusetts document, it becomes clear that the traditional way of gathering speed data requires some effort. Data from GPS companies, presumably, could make the process easier, by showing where current speed limits are too low — or too high.

Whether American police departments are actually writing more tickets because of the recession is a subject of some controversy. But the TomTom flap offers a useful reminder that the purpose of speed limits isn't to trip drivers up or to generate revenue, but to promote safety on the roads.