There are generally two types of WIM sites established over a road network:
- Temporary sites are sites installed by trained local district/regional operatives, and they do not require a high level of accuracy. Temporary sites can be used to gain knowledge of what loads are on different subsets of the network and generally do not have their results added into the WIM database.
- Permanent and pristine (PP) sites are high accuracy, corporate sites across the network. They provide the highest standard (technically and telemetrically and in terms of proofing against vandalism and fires/flooding, etc.). They also require the highest standard of monitoring and upkeep.
A WIM network is generally built upon the coverage of permanent sites.
The details of WIM sites and their T (temporary) or P (Permanent) status are recorded in WIM site status reports which are regularly updated by the agency managing the road network.