Low Speed and High Speed WIM

Often a first distinction in types of WIM is made based on the speed range the vehicles pass the WIM sensors and the conditions at the site.

1. Low speed weigh-in-motion (LS-WIM, see the left picture below): the weighing is done on a dedicated area, mostly outside the traffic lane, on a flat and smooth platform (generally in concrete), longer than 30 m, and at a velocity below 5 to 10 km/h, in order to eliminate the dynamic effects of the vehicle and to assume that the tire impact forces are equal to the wheel static loads. LS-WIM uses mainly load cell scales and is legally approved for direct enforcement or trade.

2. High speed weigh-in-motion (HS-WIM, , see the right picture below): the weighing is done in the traffic lane at current speed (i.e. 60 to 90 or 100 km/h), without slowing down or stopping the vehicles. The measurements are affected by the vehicle dynamics (vertical accelerations), and may significantly differ from the static weights on uneven pavement surfaces.