What is Weigh In Motion (WIM)?

Weigh-in-motion (WIM) is a primary technology used for monitoring vehicle weights and axle loads on roadways. Traffic loading data collected by WIM include wheel (single or dual tires) loads, axle loads, and gross vehicle weights (GVW). These data can be reported for each vehicle that passes over a WIM sensor. In addition, WIM devices collect traffic volume, axle spacings, vehicle classification, and speed data.

Reasons for WIM

State and other highway agencies collect WIM data for many reasons, including:

• Highway planning
• Pavement and bridge design
• Freight movement studies
• Motor vehicle enforcement
• Legislative and regulatory studies (e.g., truck weight and size studies).

Motor vehicle enforcement officers use WIM:

• To collect heavy truck axle load data to plan enforcement activities
• To screen and identify specific vehicles that violate weight limits during real time on-site monitoring

Highway planners and designers use WIM data to:

• Develop summary statistics by time of day, day of week, month of year, and annually
• Develop inputs for pavement and bridge design, including equivalent single axle loadings (ESAL) and axle load distributions

Further Reference:

• Federal Highway Administration (FHWA): Weigh-in-Motion Pocket Guide