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Consideration of Roadside Features in the Highway Safety Manual

Consideration of Roadside Features in the Highway Safety Manual. Project PI: Malcolm H. Ray, P.E., PhD RoadSafe LLC mac@roadsafellc.com 207-514-5474 Presented by Team Member: Karen K. Dixon, P.E., PhD Emails: karen.dixon@oregonstate.edu OR k-dixon@tamu.edu . N C H R P 17-54.

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Consideration of Roadside Features in the Highway Safety Manual

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  1. Consideration of Roadside Features in the Highway Safety Manual Project PI: Malcolm H. Ray, P.E., PhD RoadSafe LLC mac@roadsafellc.com 207-514-5474 Presented by Team Member: Karen K. Dixon, P.E., PhD Emails: karen.dixon@oregonstate.edu OR k-dixon@tamu.edu N C H R P 17-54

  2. Objective of NCHRP 17-54 • Develop quantitative measures that can be incorporated into the HSM to evaluate the effects of roadside designs and features on the frequency and severity of lane departure crashes.

  3. 17-54 Phase I completed • Literature review • Compared RSAPv3 and the HSM • Encroachment method • Crash-based method • Recommendations for use of both methods • Analyzed sample scenarios • Very different results • Different base conditions • Different units (i.e., single vehicle crashes vs. ROR crashes) • Identified potential data sources and existing CMFs • Interim Report submitted June 6, 2012.

  4. Schedule • 17-54 Interim Report meeting: May 2012 • Modifications to RSAPv3: June 2012 • Quantitative Measures for HSM: Early 2013 • Final Report: Summer 2013

  5. Rural Two-Lane Two-Way Segments Default distribution incudes SVROR crashes (52%) and Overturned (2.5%). No separate SPF for SVRORs (Calculated as a proportion of the total). SVROR is a major crash type but SVROR is only a part of ROR. HSM SPF functional form increases with ADT (generally linear shape). Roadside Hazard Rating is the main measure of roadside condition.

  6. Rural Multi-Lane Highways Segments Default distribution includes SV crashes (77%) . SV are a major crash type for this highway type but ROR crashes are not exactly the same as SV crashes. No separate SPF for SV crashes (Calculated as a proportion of the total). HSM SPF functional form increases with ADT (generally linear shape).

  7. Urban and Suburban Arterial Segments A separate SPF for SV crashes by road type. SV overlaps with ROR but is not the same. Different coefficients for the SPF based on road type. Separate SPFs for vehicle-pedestrian and vehicle-bicyclist. Non-linear relationship between ADT and crash frequency.

  8. Freeway Segments Research just completed Not part of the NCHRP 17-54 Contract

  9. Conclusions • The current SPFs for each road types handle ROR crashes differently. All lump ROR crashes in with something else (i.e., SV or SVROR) • Per Panel Instructions, Project 17-54 will develop new RORSPFs and CMFs for each road type • Phase II – Rural 2-lane and multilane (current effort) • Phase III – Urban and Suburban

  10. Expectations for Use • RSAPv3 will continue to be the go-to tool for the analysis of detailed roadside design scenarios and the development of roadside policy. • The new HSM ROR Predictive method and companion CMFs will be the go-to tool for preliminary design and scoping of roadside issues.

  11. Questions to Consider How should we integrate these new SPFs into an updated HSM? - A new section in each chapter for ROR? - A new chapter on ROR? - How do we handle inconsistencies between the new ROR SPFs and the existing ones? What about double counting?

  12. While some things have changed… Some remain the same!

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