(Garmin image)

I never quite believed those studies that contended GPS devices will help people drive greener.  What, so they don’t make as many wrong turns? I can read a map as good as the next person, thank you very much.

But now, GPS-world may be getting somewhere. Garmin is planning to come out with a new add-on cable that somehow communicates not only with the GPS satellites, but also your car’s diagnostics.  Then it gives you all sorts of readouts on your current fuel economy and scores your braking and acceleration.

In other words: Pretty much the same stuff that I get on my Prius, which I can attest has changed my driving significantly. Nothing like setting up a little competition with myself, monitored on the dashboard, to make me drive more sensibly.

The system is called Eco-Route. Apparently — and I can’t figure how — the system will also steer you to the route that will save the most gas, not just the one that’s the shortest or fastest. The folks at Treehugger have previewed it here.