Actually we are talking about something complex. Sure, if the vehicle has a permanently mounted body, then the height can be painted in the cab. But lots of these accidents involve artics, and it isn't the tractor unit that fails to clear the bridge, it's the trailer. By their very nature, any artic tractor unit can pull any trailer, and these can be anything between flatbed and maximum height boxes. And the load on the flatbeds could be any height. Now some operators only use one type of trailer, and these should have no issue with marking the height in the cab, but others haul a variety of trailers in the course of a days work and there is no system for reminding the driver of the height of the trailer/load once he/she has set off. Of course there's no difficulty in providing a small whiteboard or digital display for the driver to enter the height on, but the haulier has to actually provide it, and the driver has to remember to use it before setting off.