consideration of roadside features in the highway safety manual

Consideration of Roadside Features in the Highway

Safety ManualN C H R P 17-54

Project PI:Malcolm H. Ray, P.E., PhD

RoadSafe LLCmac@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

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.

Objective of NCHRP 17-54

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.

17-54 Phase I completed

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

Schedule

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.

0 5000 10000 15000 20000 25000 30000 35000 400000

0.51

1.52

2.53

2LN UNDIV

ADT

Encroa

chmen

ts/yr/mi

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).

0 100002000030000400005000060000700008000002468

101214

4LN DIV

ADT

Encroa

chmen

ts/yr/mi

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.

Freeway SegmentsResearch just completed

Not part of the NCHRP 17-54 Contract

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 ROR SPFs and CMFs for each road type

Phase II – Rural 2-lane and multilane (current effort)

Phase III – Urban and Suburban

Conclusions

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.

Expectations for Use

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?

Questions to Consider

While some things have changed…

Some remain the same!