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Planning Guidance for the Installation and Use of Technology Devices for Transportation Operations and Maintenance

ENTERPRISE Transportation Pooled Fund Study


ICWS Guideline 1 - Intersections with High Crash Rates (Reactive Approach)

Purpose: To influence driver behavior at stop-controlled intersections (typically 45 mph or greater posted speed on the major road) where right-angle crashes are the predominant crash type.

Initial Guidance:

1) The planning guidance provides guidance for the use of an ICWS device, regardless of the device configuration. If an ICWS should be considered, the device configuration will be selected by the engineer. (Note: Design guidance for ICWS developed by ENTERPRISE and other relevant resources can be found at: Design and Evaluation Guidance for Intersection Conflict Warning Systems)

2) This guideline does not mandate the use of ICWS. ICWS is one of several safety treatments that may be considered to improve safety at intersections.

3) ICWS #1 Intersections with High Crash Frequencies or Rates (Reactive Approach) and ICWS #2 Intersection Characteristics (Proactive Approach) may be used together or as stand-alone approaches for consideration of ICWS. Intersections meeting guideline criteria may not necessarily be selected for deployment of ICWS; these guidelines could be used to help agencies prioritize intersections for ICWS deployment.

4) To optimize the effectiveness of ICWS by reducing the likelihood of continuous alert activation, the following maximum ADT volumes should be considered:

  • Major Road ADT typically does not exceed 12,000. (1)
  • Minor Road ADT typically does not exceed 3,000. (1)

5) Engineering judgment should be used to assess potential implications that may result from installation of ICWS at candidate intersections.


(1) Athey Creek Consultants.  Design Guidance and Evaluation for Intersection Conflict Warning Systems. 2011.


  Device should be considered if:  

1. Crashes or Crash Rate at the intersection are higher than expected over a 5-year period for a region, with agency-specific thresholds as determined by using one of the following:

a) The 5-year Crash Rate (per million entering vehicles) is higher than an agency-defined threshold for the Average Crash Rate in a region.

Crash Rate = N x 10^6/ ((∑ ADT ) x 5 years x 365 days)

N = the total number of crashes at the intersection during a 5-year period

∑ ADT = the sum of average daily traffic entering the intersection


b) The total number of crashes over a 5-year period exceeds an agency-defined threshold that is higher than expected in a region.


2. One or both of the  following conditions is observed at the intersection:

a) Limited sight distance


b) Poor gap acceptance for the minor road driver is observed at the site (e.g. actual crashes and/or near misses)

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