In the US, there's a system called PrePass[1]. It's intention is to be used to allow a truck to bypass weigh-ins. The in-vehicle transponder has a red and green

In the US, there's a system called PrePass[1]. It's intention is to be used to allow a truck to bypass weigh-ins. The in-vehicle transponder has a red and green light on it. It could be repurposed to flash red when the vehicle triggers a too-tall warning, though this would be of minimal benefit since it's a small flashing red light most likely in the driver's peripheral vision. However, I'm unsure if there's any similar system in place in Australia (or most other countries, for that matter.) [1] http://www.prepass.com/services/prepass/Pages/PrePassTransponder.aspx http://www.prepass.com/services/prepass/Pages/PrePassTranspo...