 Once removed, they no longer are valid, so each car on Austrian Autobahns needs its own toll sticker.Since 2004 trucks must carry the "GO-Box", a little white box which counts the length of the Autobahn used by way of electrical control points, queried by overhead DSRC microwave radio transceivers at different locations.Overhead 3-D infrared laser scanners are used to detect and photograph trucks travelling without it.