A related method is used commercially for self-weighing trucks. Typically it's done by measuring change in the pressure in the suspension airbags and needs to be calibrated for the specific suspension and airbags being used. One major vendor lists the accuracy as +/- 300 lbs which is pretty good for use in the 30-40 ton range but not so good for a passenger vehicle.
As a bit of cool technology trickery, the Air-Weigh system encodes the weight data onto the existing tractor-trailer electrical connection so that the weight can be displayed in-cab without any extra wiring to connect. They don't say much about how but I'd guess RF modulation on the electrical for the lights or something.
As a bit of cool technology trickery, the Air-Weigh system encodes the weight data onto the existing tractor-trailer electrical connection so that the weight can be displayed in-cab without any extra wiring to connect. They don't say much about how but I'd guess RF modulation on the electrical for the lights or something.