It depends which length scales you are interested in. For road roughness related to the ride behaviour of vehicles (wavelength > 0.1m), you can use a laser scanner directly mounted to a vehicle, and the vehicle can be driven at normal road speeds. Many road authorities around the world do this kind of scanning every day. For road roughnesses related to tyre noise (0.001m) you need very high speed data collection, or to drive the vehicle very slowly!. For roughnesses related to tyre friction (