safetyanalyst michael s. griffith fhwa july 2003
TRANSCRIPT
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