All-way Stop Control Intersection

Safety performance functions, development (calibration, crash modification factors [Part C], crash proportions), IHSDM and other software

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All-way Stop Control Intersection

Postby cmilner » Thu Sep 27, 2012 10:49 am

I have an existing rural two-lane, four-leg intersection with stop control on major and minor approaches. This type of intersection is not defined as an intersection site type covered in Chapter 10 of the HSM. Any insight as to why this intersection type is not covered?

Any suggestions for applying the predictive model to this project given the unavailability of the all-way stop control site type in the current edition Predictive Method? I have 10 years of crash data and the remainder of the project is covered under the Chapter 10 site types.
Chris Milner, PE, PTOE
Shive-Hattery, Inc.
cmilner@shive-hattery.com
cmilner
 
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Re: All-way Stop Control Intersection

Postby Mohamad Banihashemi » Fri Sep 28, 2012 12:52 pm

The original Crash Prediction Module of the IHSDM Software had an AMF (now called CMF) for stop-controlled intersections that was showing the difference between minor-road stop controlled (as base condition) and all-way stop controlled intersections. It was 0.53. After these prediction models were evolved to what is now Chapter 10 of the HSM there were some additions to the models and some deletions. CMF for all-way stop controlled intersections was one of the components that was eliminated, may be because the reviewers of the models did not have enough evidence to confirm that. There is also CMF=0.52 in the 14th Chapter of the HSM (Table 14-5, page 14-12) that supports the hypothesis that converting a minor-road stopped controlled intersection to an all-way stop controlled intersection decreases the intersection crashes significantly. The Standard Error of this CMF is very low (0.04) and considered most reliable ny HSM standards. These two CMFs are almost the same and I am not sure if they have different refrences. Whether you want to combine these CMFs with the HSM Chapter 10 models is up to you. Since there is no model for all-way stop controlled intersections in Chapter 10, if you really need to have prediction for your intersections of this type i suggest you set them as minor-road stop-controlled intersections and apply the CMF of 0.52 to their share of the prediction.
Mohamad Banihashemi
 
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Re: All-way Stop Control Intersection

Postby cmilner » Fri Sep 28, 2012 1:12 pm

Thank you for your insight Mohamad.
Chris Milner, PE, PTOE
Shive-Hattery, Inc.
cmilner@shive-hattery.com
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Joined: Mon Sep 17, 2012 11:25 am
Location: Iowa City, IA


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