O VERVIEW OF THE N EW H IGHWAY S AFETY M ANUAL Karen Dixon, Oregon State University NCHRP Project Member AASHTO Subcommittee on Traffic Engineering June 16, 2009 Manchester, NH

P RESENTATION S UMMARY

I. WHAT IS THE HSM? Overview of the new HSM

W HAT IS THE HSM?

T HE V ISION OF THE HSM - A D OCUMENT A KIN T O THE HCM 1 2 3

W HAT THE HSM IS NOT The HSM does not set requirements or mandates The HSM is not a best practice document for design or operations. The HSM contains no warrants or standards and does not supersede other publications that do. vs

The HSM does not establish a legal standard of care nor does it create a duty to the public.

II. W HY D O W E N EED THE HSM? Overview of the new HSM

I S T HIS R OAD “S AFE ” OR “U NSAFE ”? What does safety really mean?

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 H IGHWAY S AFETY H AS T WO D IMENSIONS *Ezra Hauer, ITE Traffic Safety Toolbox Introduction, 1999

U NLIKE N OMINAL S AFETY, S UBSTANTIVE S AFETY IS A C ONTINUUM

CRASH RISK DESIGN DIMENSION Lane Width, Radius of Curve, Stopping Sight Distance, etc. CRASH RISK DESIGN DIMENSION Lane Width, Radius of Curve, Stopping Sight Distance, etc. U NLIKE N OMINAL S AFETY, S UBSTANTIVE S AFETY IS A C ONTINUUM Substantive Safety Nominal Safety

N OMINAL S AFETY VS S UBSTANTIVE S AFETY CRASH RISK DESIGN DIMENSION Lane Width, Radius of Curve, Stopping Sight Distance, etc. Low Nominal Low Substantive Low Nominal Low Substantive Low Nominal High Substantive Low Nominal High Substantive High Nominal Low Substantive High Nominal Low Substantive High Nominal High Substantive High Nominal High Substantive

S UBSTANTIVE S AFETY M AY V ARY W HEN N OMINAL S AFETY D OES N OT Existing Conditions Alternative 1 Alternative 2 Alternative 3

W E ’ RE I NTERESTED IN O THER I MPACTS FOR P ROJECT L EVEL D ECISIONS – W HAT A BOUT S UBSTANTIVE S AFETY ? Safety Environmental Traffic Right-of-Way Costs Impacts Impacts Operations Traffic Noise Model 1.0 CAL3QHC Mobile 5a 3-D Visualization CITYGREEN HCM CORSIM PASSER TRANSYT7F VISSIM Construction Plans Cost Models Real estate appraisals DOT databases Design Criteria (nominal safety) More quantitative Greater weight The HSM

T HE HSM C ONTAINS B EST S CIENCE & R ESEARCH Synthesis of previous research New research commissioned by AASHTO and FHWA

III. HOW WAS THE HSM DEVELOPED? Overview of the new HSM

T HE HSM – A T EN - YEAR R ESEARCH A ND D EVELOPMENT E FFORT Future Research, research and more research

S IGNIFICANT E FFORT & P ROFESSIONAL S UPPORT P RODUCED THE HSM Joint Subcommittee sponsored by 7 TRB committees Thousands of hours of volunteer effort Research program funded by NCHRP, AASHTO & FHWA

NCHRP Project 17-18(04) Development of a HSM - Draft Table of Contents for the HSM. NCHRP Project Crash Reduction Factors for Traffic Engineering and ITS Improvements NCHRP Project Development of Models for Prediction of Expected Safety Performance for Urban and Suburban Arterials NCHRP Project Prepare Parts I and II of the HSM NCHRP Project Safety Prediction Models for Rural Multilane Highways for Use in the HSM NCHRP Project Prepare Parts IV and V of the HSM NCHRP Project Production of the First Edition of the HSM NCHRP Project Pedestrian Predictive Crash Methodology for Urban and Suburban Arterials NCHRP Project HSM Implementation and Training Materials R ESEARCH P ATH TO THE HSM V.1

IV. W HAT IS C OVERED BY THE HSM? Overview of the new HSM

O UTLINE OF THE HSM

PART A INTRODUCTION, HUMAN FACTORS, & FUNDAMENTALS Introduction and Overview Chapter 1 Human Factors Chapter 2 Fundamentals Chapter 3

P ART B R OADWAY S AFETY M ANAGEMENT P ROCESS Network Screening Diagnosis Countermeasure Selection Economic Appraisal Prioritization of Improvement Projects Safety Effectiveness Evaluation

P ART C P REDICTIVE M ETHOD Methodology Applications Safety issues not explicitly addressed by the methodology Example problems References Special Part C Common Procedures Calibration Combining predicted with observed crashes

D EFINITION OF HSM T ERMS Safety Performance Function (SPF) – a regression equation used for estimating the predicted crash frequency at a site for a given “base condition” Accident Modification Factor (AMF) – used to adjust the “base condition” in the SPF to specific site characteristics Calibration Factor (C) – adjusts average crash frequencies calculated from the SPF to local site conditions

P REDICTING C RASHES – D EFINING R OADWAY S EGMENTS AND I NTERSECTIONS

C RASH E STIMATION E QUATION N predicted = N spf x C x AMF1 x AMF2 x … Calculate the Roadway Segment N predicted and the Roadway Intersection Segment N predicted separately

S UMMATION OF C RASHES

HSM R EGIONAL SPF C ALIBRATION Step 5 – Compute calibration factors for use in Part C predictive model Step 1 – Identify facility types of interest Step 2 – Select sites for calibration of each facility type Step 3 – Obtain data for each facility type applicable to the calibration period Step 4 – Apply the appropriate Part C predictive model to estimate expected crash frequency for each site during the calibration period

C ALIBRATION S TEP 1 – F ACILITY T YPES Roadway SegmentsIntersections Rural 2-lane roads 2-lane undivided3-leg & 4-leg with minor road STOP 4-leg signalized Rural multilane roads Undivided segments Divided segments 3-leg & 4-leg with minor road STOP 4-leg signalized Urban and suburban arterials 2-lane & 4-lane undivided 3-lane & 5-lane with TWLTL 4-lane divided 3-leg & 4-leg with minor road STOP 3-leg & 4-leg signalized

C ALIBRATION S TEP 2 – S ELECT S ITES FOR C ALIBRATION OF F ACILITY T YPES Each facility type will need a minimum of 30 to 50 sites. Calibration sites should be based on road segments or intersections as shown in Step 1 Total crashes observed at all sites unique to a specific facility type should be a minimum of 100 per year – this should not be investigated until after the sites are selected

C ALIBRATION S TEP 3 – O BTAIN DATA FOR EACH F ACILITY T YPE Total observed crash frequency for a period selected (usually 1 to 3 years) Site characteristic data complying with required versus desirable data elements as shown in the following slides

D ATA E LEMENT N EEDS

D ATA E LEMENT N EEDS ( CONTINUED )

C ALIBRATION S TEP 4 – A PPLY P REDICTIVE M ETHOD Apply the applicable HSM Part C predictive method to predict total crash frequency for each site during the calibration period

C ALIBRATION S TEP 5 – C OMPUTE C ALIBRATION F ACTORS Create a proportional factor to apply to regional data as follows:

W HAT IS THE E MPERICAL B AYES (EB) M ETHOD ? Tool to compensate for the potential bias due to regression-to-the-mean Correct for unusual crash trends Uses predicted crashes paired with observed crashes for a more reliable crash estimate

P ART D A CCIDENT M ODIFICATION F ACTORS Roadway Segments CHAPTER 13 Intersections CHAPTER 14 Interchanges CHAPTER 15 Special Facilities and Geometric Situations CHAPTER 16 Road Networks CHAPTER 17

V. WHO SHOULD USE THE HSM? Overview of the new HSM

W HO S HOULD U SE THE HSM?

Assess the system needs & identify projects/studies Program projects Evaluate system-wide safety effects of programs

Define problem(s) and assist in scoping Identify potential solutions Assess or evaluate multiple alternatives and expected quantitative safety effects Aid in identification of a preferred alternative

Evaluate safety of alternative design approaches Assist in review & documentation of design exceptions, variances and waivers Inform decisions on construction staging, work approaches, etc.

Monitor operations to maintain balance among safety, mobility and access. Evaluate the effectiveness of implemented improvements

VI. W HEN W ILL THE HSM BE A VAILABLE ? Overview of the new HSM

I MPLEMENTATION S CHEDULE Now through July 31, 2009: Review & balloting by AASHTO ‘s Subcommittee of Traffic Engineering, Standing Committee on Highway Traffic Safety, and Subcommittee on Design Sept 1 st to 30 th, 2009 – Ballot by AASHTO’s Standing Committee on Highways & Standing Committee on Highway Traffic Safety Expected Release Date: Early 2010

T RAINING & O UTREACH A CTIVITIES Sept 2009 – Jan 2010 – Conduct two or three multi-state pilot courses August 2009 – TRB Task Force Meeting TRB 2010 Annual Meeting – One-day workshop Training materials, including “Train-the- trainer” available upon HSM release

VII. W HERE C AN O NE F IND M ORE I NFORMATION A BOUT THE HSM? Overview of the new HSM

DATA NEEDS GUIDE

K EY C ONTACTS AASHTO – Ken Kobetsky: (202) – Jim McDonnell: (202) – Joel McCarroll: (202) 624- AASHTO JOINT TASK COMMITTEE FOR THE HSM – Don Vaughn, ALDOT, (334)

K EY C ONTACTS TRB/ NCHRP – Rick Pain: – Chuck Niessner: (202) TRB HSM TF: Development of a Highway Safety Manual – John Milton, TRB HSM TF: User Liaison – Geni Bahar (User Liaison Subcommittee of the TRB HSM Task Force): (416) TRAINING – Karen Dixon (PI of NCHRP Project 17-38): (541)

T HE E ND Questions?