What it means
Fixed gantries cover the same point every day. Drivers learn where they are. A mobile system moves enforcement to accident blackspots, temporary works zones and roads where a gantry is too costly. The vehicle can work while parked at the roadside or while moving with traffic, depending on the design.
The key requirements are a quick start (the officer should not need to calibrate anything), GPS location on every record, and a review step before a challan is issued.
How it applies in India
Rule 167A of the Central Motor Vehicles Rules lists speed guns, body-worn cameras and dashboard cameras among electronic enforcement devices, alongside fixed cameras. In India, mobile enforcement also checks documents: a plate read can be matched against VAHAN and SARATHI records for registration, insurance and licence status. Stellarview MTES runs on interceptor vehicles used by the Maharashtra Motor Vehicles Department and Maharashtra Police.