{ "culture": "en-US", "name": "", "guid": "", "catalogPath": "", "snippet": "This dataset contains the Roads and Highways Road Network Linear Referencing System (LRS) HPMS grade event polyline feature class which identifies roadway grade information for Idaho\u2019s public roadway segments as reported through the Highway Performance Monitoring System (HPMS). The data supports roadway design, safety analysis, and performance modeling by describing the longitudinal slope of the roadway surface.", "description": "
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. <\/SPAN><\/P> Grade information is derived from roadway centerline geometry, design plans, and digital elevation data maintained in ITD\u2019s 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. <\/SPAN><\/P> 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\u2019s Highway Performance Monitoring System (HPMS) reporting to the Federal Highway Administration (FHWA). <\/SPAN><\/P>