SafetyAnalyst

Michael S. Griffith

FHWA

July 2003

2

What is SafetyAnalyst?

Vision Statement

• Provide state-of-the-art analytical tools for use in the decision making process to identify and manage a systemwide program of site-specific improvements to enhance highway safety by cost-effective means

3

Why is SafetyAnalyst Being Developed?

• Both FHWA and participating state highway agencies have perceived a need to improve the analytical tools available to highway agencies for safety management of the highway system

4

Participating States

5

Who is DevelopingSafetyAnalyst?

• Federal Highway Administration

• Technical Working Group, 13 participating states

• Midwest Research Institute and subcontractors

• ITT Industries, Software development contractor

6

Tools for Safety Management

To assist agencies in making better decisions about:

Where to make highway safety improvements

Determining what improvements to make

Evaluating the effectiveness of implemented safety improvements

7

Target Audience

Professionals involved in deciding:

Where to make highway safety improvements

Determining what improvements to make

Evaluating the effectiveness of implemented safety improvements

8

Scope

• Addresses site-specific improvements based on site-specific needs, not general programs like vehicle design improvements, occupant restraints, etc.

• Uses state-of-the-art technology to advance the state of the practice

• Should be comprehensive – including all stages of the safety management process

9

What Tools will be Available in SafetyAnalyst?

• Network screening to identify sites with promise for safety improvement

• Diagnosis of safety concerns

• Selection of countermeasures

• Economic appraisal of countermeasures

• Priority ranking of countermeasures

• Evaluation of implemented projects

10

Network Screening

• Review entire roadway system or selected parts – roadway segments, intersections, ramps, railroad grade crossings, etc.

• Identify sites with promise for safety improvement

• Rank sites with promise for safety improvement

• Select sites as candidates for diagnosis

11

Types of Network Screening

• Basic network screening

• Screening for high proportions of specific target accident types

• Detection of safety deterioration

• Screening for high frequency of specific target accident types

• Screening for corridors with promise

12

Basic Network Screening

• Two screening approaches:– sliding window

– peak searching

• Two measures of potential for safety improvement:– expected accident frequency

– expected excess accident frequency

13

Diagnose Safety Concerns at Selected Sites

• Consider both sites with promise identified by network screening tool and from other sources

• Identify accident patterns• Investigate causal factors• Consider site conditions and safety

performance from engineering and human factors viewpoints

• Assess whether a potentially correctable safety concern exists

14

Select Appropriate Countermeasures

• Present lists of countermeasures that are potentially appropriate for identified accident patterns and safety concerns

• Final selection made by user

• Where appropriate, user may select:– combination of countermeasures

– alternative countermeasures for economic appraisal and priority ranking

Economical Appraisal and Priority Ranking

• Assess the cost-effectiveness of candidate countermeasures

• Rank candidate countermeasures to assist choices among them

• Select an optimal program of countermeasures to maximize systemwide safety benefits

Types of Economic Appraisal

• Cost-effectiveness

• EPDO-based cost-effectiveness

• Benefit-cost ratio

• Net benefits

Optimization

• Considers multiple sites selected by the user

• User specified total budget constraint

• Optimization routine selects countermeasures to maximize safety benefits within budget constraint

Evaluation

• Assess the effectiveness of countermeasures based on a formal before-after evaluation

• Evaluation results should be suitable for future use as AMFs in SafetyAnalyst

19

Scope of Evaluation

• Evaluation types:– percent change in accident frequency

– change in proportion of target accident types

20

How Will Safety AnalystBe Implemented?

• SafetyAnalyst will be implemented as a set of integrated software tools to perform key steps in the safety management process

• SafetyAnalyst will be made available to highway agencies by FHWA

• SafetyAnalyst will be maintained as the state of knowledge advances

21

What Is the Planned Schedule?

• “New Approaches to Highway Safety Analysis“ training course – Fall 2003

• Release interim tools – 2004

• Release final tools – 2006

22

SafetyAnalyst Website

www.safetyanalyst.org