HPMS Grade

The Idaho Transportation Department's (ITD) Roads and Highways Road Network Linear Referencing System (LRS) HPMS grade event polyline feature class represents the longitudinal slope, or steepness, of a roadway segment. Grade is a key geometric characteristic that influences vehicle performance, fuel consumption, drainage, and roadway safety. It is expressed as a percentage based on the rise or fall in elevation over a given horizontal distance. Grade information is derived from roadway centerline geometry, design plans, and digital elevation data maintained in ITD’s roadway inventory and HPMS systems. Both upgrade (positive) and downgrade (negative) values are recorded to indicate direction of slope relative to increasing route mile point. This dataset is used by engineers, planners, and safety analysts to evaluate roadway performance, assess design compliance, and identify locations where steep grades may affect vehicle operations or maintenance needs. Grade data is updated annually as part of ITD’s Highway Performance Monitoring System (HPMS) reporting to the Federal Highway Administration (FHWA). This layer is an export from Roads and Highways that represents only the active records within the LRS. These are current “working” records. For the static, published data, please see the records stored at: https://www.fhwa.dot.gov/policyinformation/hpms.cfm This content item is a sub-layer of the Highway Performance Monitoring System (HPMS) authoritative feature layer. Metadata