1. Highway Safety Manual
DAY 2 - HSM Practitioners Guide for Multilane Rural Highways and Urban Suburban Streets
Cover Slide for the one-day NHI format 2010 AASHTO Highway Safety Manual Practitioners Guide for Multilane Rural Highways and Urban Suburban Streets workshop. This one-day workshop is the former NHI B course which has been updated to the final version 4.0 Highway Safety Manual as published by AASHTO in June of 2010.
Workshop participants are provided the technical information of Chapters 11 and 12 and examples of how to apply this technical information and will be able to use the tools of the Highway Safety Manual effectively upon completion of this workshop.
Workshop includes exercises as adult learning activity to apply the technical information of the Highway Safety Manual to real world locations.

2. Review from DAY 1
Session #1 – Introduction and Background for HSM Rural Multilane and Suburban Urban Streets
Length of Session 01 is 35 minutes which means that the instructor needs to move this session right along and not take up too much time with introduction and issue identification.

3. Introduction and Background
HSM Applications to Multilane Rural Highways and Urban Suburban Streets
Introduction and Background
- Session #1
Session #1 – Introduction and Background for HSM Rural Multilane and Suburban Urban Streets
Length of Session 01 is 35 minutes which means that the instructor needs to move this session right along and not take up too much time with introduction and issue identification.

4. HSM Applications to Multilane Rural Highways and Urban Suburban Streets
Learning Outcomes:
Review Crash Frequency Performance of Rural Multilane Segments and Intersections
Learning Outcomes for Session #1 Introduction and Background

5. HSM Practitioner's Guide for Two-Lane Rural Highways
August 2010
HIGHWAY SAFETY MANUAL
Multilane Rural Highways and Urban Suburban Streets
1.1. Purpose and Intended Audience:
The Highway Safety Manual (HSM) provides analytical tools and techniques for quantifying the potential effects on crashes as a result of decisions made in planning, design, operations, and maintenance. There is no such thing as absolute safety. There is risk in all highway transportation. A universal objective is to reduce the number and severity of crashes within the limits of available resources, science, and technology, while meeting legislatively mandated priorities. The information in the HSM is provided to assist agencies in their effort to integrate safety into their decision-making processes. Specifically, the HSM is written for practitioners at the state, county, metropolitan planning organization (MPO), or local level. The HSM’s intended users have an understanding of the transportation safety field through experience, education, or both. This knowledge base includes:
■■ ■Familiarity with the general principles and practice of transportation safety;
■■ ■Familiarity with basic statistical procedures and interpretation of results; and
■■ ■Suitable competence to exercise sound traffic safety and operational engineering judgment.
The users and professionals described above include, but are not limited to, transportation planners, highway designers, traffic engineers, and other transportation professionals who make discretionary road planning, design, and operational decisions. The HSM is intended to be a resource document that is used nationwide to help transportation professionals conduct safety analyses in a technically sound and consistent manner, thereby improving decisions made based on safety performance.
Documentation used, developed, compiled, or collected for analyses conducted in connection with the HSM may be protected under Federal law (23 USC 409). The HSM is neither intended to be, nor does it establish, a legal standard of care for users or professionals as to the information contained herein. No standard of conduct or any duty toward the public or any person shall be created or imposed by the publication and use or nonuse of the HSM.
The HSM does not supersede publications such as the U.S. DOT FHWA’s Manual on Uniform Traffic Control Devices (MUTCD), Association of American State Highway Transportation Officials’ (AASHTO’s) “Green Book” titled A Policy on Geometric Design of Highways and Streets, or other AASHTO and agency guidelines, manuals, and policies. If conflicts arise between these publications and the HSM, the previously established publications should be given the weight they would otherwise be entitled if in accordance with sound engineering judgment. The HSM may provide needed justification for an exception from previously established publications.

6. Multilane Highways - Expressways:
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Multilane Highways - Expressways:
Constructed since the early 1950’s
Expressways are less expensive to build
no grade separation Intersections (less $$)
not full access control (less $$)
Instructor:
From October 2006 for 2005 US public roads inventory report
Session 1 – Introduction and Background

7. Multilane Highways (Rural&Urban):
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Multilane Highways (Rural&Urban):
3,995,644 miles – US Public Roads
976,477 miles - US Federal Aid Mileage
165,783 miles - Multilane Highways 17%
44,673 miles – Multilane Undivided 27%
121,100 miles – Multilane Divided %
65,357 miles - Multilane rural highways
Instructor:
From October 2006 for 2005 US public roads inventory report
Session 1 – Introduction and Background

8. Rural Expressway Mileage:
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Rural Expressway Mileage:
From NCHRP 650, Table 1 published Sept 2010 Dr. Tom Mays
*NCHRP 650
Session 1 – Introduction and Background

9. Safety Performance of Rural Multilane Highways:
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Safety Performance of Rural Multilane Highways:
Crash rate on rural expressways (0.9 crashes per mvm) less than for rural 2-lane Highways (1.0 crashes per mvm)
Severities on rural expressways (1.2 deaths per 100 mvm) less than for rural 2-lane Highways (1.5 deaths per 100 mvm)
When access density is low, crash rate is similar to rural freeway (0.52 per mvm)
Instructor:
From NCHRP 650 – results are by Minn Dot
* Minn DOT, NCHRP 650
Session 1 – Introduction and Background

10. Example from nchrp 650 of crash rates
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Instructor:
Example from nchrp 650 of crash rates
Please note that the crash rates (crashes/million vehicle miles) for 4-lane rural divided expressways are significantly lower for fatal and somewhat lower for injury and actually more than rates for 2-lane hwys planned for conversion to 4-lane divided.
Session 1 – Introduction and Background

11. Approaches for Considering Safety
Nominal Safety
Substantive Safety
Examined in reference to compliance with standards, warrants, guidelines and sanctioned design procedures
The expected or actual crash frequency and severity for a highway or roadway
Instructor:
Nominal Safety literally means “Safety” in name only
This was the traditional way of presenting the “safety” associated with geometric values presented in the AASHTO Green Book and in the state design standards and in the national MUTCD. That is, for a certain width of traffic lane or shoulder, meeting that value had the meaning of being a “safe” design which is far too simplistic a way to think of safety performance. There are many roads that have lane width and shoulders less than the minimum values of the green book that have fewer crashes than the average. See the 3rd paragraph of the forward of the Green Book
Substantive safety is the actual crash frequency and severity of a highway or intersection. Substantive Safety performance and philosophy were created by Esira Hauer in the mid 1990’s; the Substantive Safety philosoply has been embraced by AASHTO and is a tenant of the practice of professional transportation today.
*Ezra Hauer, ITE Traffic Safety Toolbox Introduction, 1999

12. Substantive Safety is a Continuum
HSM Practitioner's Guide for Two-Lane Rural Highways
Substantive Safety is a Continuum
August 2010
Which model more closely describes what stakeholders are thinking?
Key Message: Substantive safety is not a yes/no or black/white thing (as is nominal safety). Rather, it is a continuum that is often non-linear. Thus, a slight degradation in stopping sight distance (or alternatively, a slightly sharper curve, or narrower shoulder, etc.) should not be expected to produce a significantly different performance in terms of crashes.
Additional Info: This is a very important insight. Note that at some point on the continuum, as a design value or other feature degrades, one should expect the safety consequences to begin to be seen. There is not a large body of work that is available to support just where on the continuum safety problems will begin to develop. Two lane rural roads are fairly well defined, other facilities not as much.
If you only apply nominal safety, your discussions with stakeholders will only center on safe vs. unsafe. In actuality, most design values follow a continuum of safety where changes in design values may represent only a slight increase in safety risk. In discussing safety tradeoffs, stakeholders are thinking orange line while engineers look at the blue line.
Question/Interactivity: The instructor should use this graphic to point out where design criteria typically reside in the continuum (well to the right).
Reference:

13. Nominal and Substantive Safety
Safety and Operational Effects of Geometric Design Features for Multilane Rural Highways Workshop
April 2009
Example:
1st Step
2nd Step
Nominal Safety:
Rural Multilane intersection design has median opening
(CMF = 1.00)
Substantive Safety
Use Positive Offset alignment Left Turning Lanes
CMF = 0.52 which is 48% fewer total crashes
Instructor:
No left turn lane in a multilane rural highway is the base condition for rural multilane highway intersections.
CMF2i—Intersection Left-Turn Lanes
The SPF base condition for intersection left-turn lanes is the absence of left-turn lanes on all of the intersection approaches.
The CMFs for presence of left-turn lanes are presented in Table for total crashes and injury crashes.
These CMFs apply only on uncontrolled major-road approaches to stop-controlled intersections. The CMFs for
installation of left-turn lanes on multiple approaches to an intersection are equal to the corresponding CMF for installation
of a left-turn lane on one approach raised to a power equal to the number of approaches with left-turn lanes
(i.e., the CMFs are multiplicative, and Equation 3-7 can be used). There is no indication of any effect of providing
a left-turn lane on an approach controlled by a stop sign, so the presence of a left-turn lane on a stop-controlled approach
is not considered in applying Table The CMFs for installation of left-turn lanes are based on research
by Harwood et al. (4) and are consistent with the CMFs presented in Chapter 14, Intersections. A CMF of 1.00 is
used when no left-turn lanes are present.
table Crash Modification Factors (CMF2i) for Installation of Left-Turn Lanes on Intersection Approaches
Intersection Type Crash Severity Level
Number of Non-Stop-Controlled Approaches
with Left-Turn Lanesa
One Approach Two Approaches
Three-leg minor-road stop
controlb
Total 0.56 —
Fatal and Injury 0.45 —
Four-leg minor-road stop control Total
Fatal and Injury
a Stop-controlled approaches are not considered in determining the number of approaches with left-turn lanes
b Stop signs present on minor-road approaches only.
Session 1 – Introduction and Background

14. Nominal and Substantive Safety
Signalized Intersections: A Guidebook Workshop
Nominal and Substantive Safety
May 2006
Example:
At 20,000 ADT
2nd Step
1st Step
Example of Nominal requirements and Substantive Safety
Where there are substantive safety shortfalls, Enhance Application of Traffic Control Devices, such as signal head per lane centered over the lane
Per table 100 of sig
26.3 crashes/mile
4.2 crashes/mile
Nominal Safety – Two 12’ wide lanes in each direction
+Add median
= Substantive Safety
Session 1 – Introduction and Background

15. HSM Applications to Multilane Rural Highways and Urban Suburban Streets
Learning Outcomes:
Reviewed Crash Frequency (Safety) Performance of Rural Multilane Intersections
Defined Substantive Safety beyond Nominal Safety
Instructor: review the learning outcomes for this module with the participants going over what they have learned.

16. Questions and Discussion:
Introduction and Background
Questions and Discussion: