N C H R P 17-54
Project PI:
Malcolm H. Ray, P.E., PhD
RoadSafe LLC
[email protected]
207-514-5474
Presented by Team Member:
Karen K. Dixon, P.E., PhD
Emails: [email protected] OR [email protected]

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.
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
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)
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Identified potential data sources and existing
CMFs
Interim Report submitted June 6, 2012.
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17-54 Interim Report meeting: May 2012
Modifications to RSAPv3: June 2012
Quantitative Measures for HSM: Early 2013
Final Report: Summer 2013
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).
Encroachments/yr/mi
Roadside Hazard Rating is the main measure of roadside condition.
3
2.5
2
1.5
1
0.5
0
2LN UNDIV
0
10000
20000
ADT
30000
40000
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).
Encroachments/yr/mi
HSM SPF functional form increases with ADT (generally linear
shape).
15
10
5
4LN DIV
0
0
20000
40000
ADT
60000
80000
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.
Research 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)
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
Phase III – Urban and Suburban
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
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.
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?