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Federal Highway Administration
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Washington, DC 20590

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Interactive Highway Safety Design Model (IHSDM): Intersection Review Module


The image shows a vehicle approaching a four-way intersection that is situated on a rural, two-lane road. The vehicle is just to the left of a yellow, diamond-shaped road sign.The Intersection Review Module (IRM) performs a diagnostic review to systematically evaluate an intersection design for typical safety concerns.

The IRM is an expert system that leads the user through a systematic evaluation of an existing or proposed intersection geometric design to identify potential safety concerns and possible treatments to address those concerns. The review considers design issues including:

  • Intersection configuration: multileg intersections, skewed intersections, offset T-intersections, and more than one minor-road approach on the same side of the major road
  • Horizontal alignment: intersection on horizontal curve, curve on intersection leg, and approach alignment differing between opposing approaches
  • Vertical alignment: intersection on crest vertical curve, crest or sag vertical curve on intersection approach, steep grade through intersection, and continuity of minor-road profile through intersection
  • Intersection sight distance


The IRM can provide useful input to project scoping, preliminary engineering, and design review.

See IHSDM Library for References.


Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101