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FHWA Home / Safety / Transportation Safety Planning (TSP) / Tools and Practices for System Wide Safety Improvement

Tools and Practices for System Wide Safety Improvement

Appendix B: Tools Supporting Safety Impact Prediction

The matrix below provides a list of all nationally available tools discussed in this report. The matrix also provides the primary purpose of each tool, key data inputs, outputs, and recommended expertise of the users. Please note that the required expertise need not exist in a single user, but a group of users should have the collective expertise required in order to utilize the tools successfully.

Tool ToolPrimary Purpose ToolKey Data Inputs ToolOutputs Tool Recommended Expertise
Safety Data Analysis Tools
Highway Safety Manual (HSM) Attachment A Provides a framework for safety that aids practitioners in selecting countermeasures, prioritizing projects, comparing alternatives, and quantifying and predicting the safety performance of roadway elements during the planning, design, construction, and operation phases Attachment B Crash Data: road location, date, crash type, severity, relationship to intersection, distance to intersection Attachment C Roadway Data: road type, segment identification, intersection type Traffic volume data such as Average Annual Daily Traffic (AADT): for intersections, major and minor street entering AADT A method to estimate crash frequency and severity and then conduct economic appraisals of improvements to use for prioritizing projects and calculating the effects of design alternatives Basic understanding of traffic engineering, statistical analysis, transportation planning, and safety management
Crash Modification Factors (CMF) Clearinghouse Provide transportation professionals with a web-based repository of CMFs and documents /training materials to support the proper application of CMFs Search parameters to determine appropriate crash modification factors Crash modification factors Basic understanding of traffic engineering, statistical analysis, transportation planning, and safety management
Interactive Highway Safety Design Model (IHSDM) Provides estimates of a highway design's expected safety and operational effects of geometric design decisions on rural two-lane highways with some applications to rural multilane highways and urban/suburban arterials Crash Data: specific road location of crash, collision type, severity Roadway Data: lane width, shoulder width/type, horizontal curve length and radius, gradation, driveway density, passing lanes, roadside hazard rating Intersection Data: traffic control, intersection skew angle, turn lanes, sight distance Traffic volume data (AADT) The IHSDM-HSM Predictive Method 2011 Release includes six evaluation modules: Crash Prediction, Policy Review, Design Consistency, Intersection Review, Traffic Analysis and Driver/Vehicle Modules. The Crash Prediction Module (CPM) supports implementation of Part C (Predictive Method) of the Highway Safety Manual (HSM) for rural two-lane highways (HSM – Chapter 10), multilane rural highways (HSM – Chapter 11) and urban and suburban arterials (HSM – Chapter 12). The other IHSDM evaluation modules are applicable to rural two-lane highways. Basic understanding of geometric design concepts, ability to input data in Microsoft (MS) Windows environment through conversion of detailed geometric designs from other software or comma-separated file format (*.csv)
SafetyAnalyst A set of computerized analytical tools to identify safety improvement needs and supports use of cost- effectiveness analysis to develop a system-wide program of site-specific improvement projects Crash Data: location, date, collision type, severity Roadway Data: segment number, segment location (in a form linkable to crash locations), segment length (mi), area type (rural/urban) Intersection Data: intersection number, intersection location (in a form linkable to crash locations), area type (rural/urban), number of intersection legs, type of intersection traffic control, major-road traffic volume (AADT), minor-road traffic volume (AADT) Ramp Characteristics Data: ramp number, ramp location (in a form linkable to crash locations), area type (rural/urban), ramp length (mi), ramp type, ramp configuration (diamond/loop/directional/etc.), ramp traffic volume (AADT) The Network Screening Tool identifies sites with potential for safety improvements. The Diagnosis Tool diagnoses the nature of safety problems at specific sites. The Countermeasure Selection Tool assists users in selecting countermeasures to reduce crash frequency and severity at specific sites. The Economic Appraisal Tool performs an economic appraisal of a specific countermeasure or alternative countermeasures for a specific site. The Priority Ranking Tool provides a priority ranking of sites and proposed improvement projects based on the benefit and cost estimates determined by the economic appraisal tool. The Countermeasure Evaluation Tool provides the capability to conduct before/after evaluations of implemented safety improvements. Understanding of traffic engineering, statistical analysis, transportation planning, and safety management
Systemic Safety Project Selection Tool The systemic approach to safety involves widely implemented improvements based on high-risk roadway features correlated with specific severe crash types. The approach provides a more comprehensive method for safety planning and implementation that supplements and compliments traditional site analysis. It helps agencies broaden their traffic safety efforts and consider risk as well as crash history when identifying where to make low-cost safety improvements. Crash Data Roadway Data Cost/Benefit data for specific roadway treatment strategies Reduced risk of and the potential for the occurrence of future crashes. Basic understanding of traffic engineering, statistical analysis, transportation planning, and safety management
Highway Performance Monitoring System (HPMS) Viewer and Geographic Information System (GIS) Tools GIS software turns statistical data such as crashes and geographic data such as roads and crash locations into meaningful information for spatial analysis and mapping Crash Data
Roadway Data
Traffic Operations Data
Provides graphical displays to support: Spot/Intersection Analysis
  • Strip Analysis
  • Cluster Analysis
  • Sliding-Scale Analysis
  • Corridor Analysis
Experience using GIS software
PlanSafe Forecasting tool that enables state DOTs and MPOs to account for sociodemographic induced changes and infrastructure changes when forecasting safety impacts Demographic Data: population, travel patterns, infrastructure (residential, commercial, etc.) Crash Data Predictive crash data based on expected changes to population Experience using GIS software, statistical modeling, statistical analysis
U.S. Road Assessment Program (usRAP) A method to benchmark the safety performance of specific roadway segments in comparison to similar roadways Crash Data: specific road location of crash Roadway Data: road type, section length, traffic volume (ADT) Color coded maps that show:
  • fatal and serious injury crashes per mile of road,
  • fatal and serious injury crashes per hundred million vehicle-miles of travel,
  • ratio of fatal and serious injury crash rate per hundred million vehicle miles of travel to the average crash rate for similar roads,
  • potential number of fatal and serious injury crashes saved per mile in a specified time period if crash rate per hundred million vehicle- miles were reduced to the average crash rate for similar roads,
  • supplemental maps (similar to types above) that address specific crash types (e.g., roadway departure, drug or alcohol involved)
GIS cartography to assign crash coordinates to a specific roadway segment is preferred
Pedestrian and Bicycle Safety Tools
Pedestrian and Bicycle Crash Analysis Tool (PBCAT) Software to assist state and local pedestrian/bicycle coordinators, planners and engineers with improving walking and bicycling safety through analysis of a database containing details associated with crashes between motor vehicles and pedestrians or bicyclists Crash Data: date, time, location, demographics of involved parties, subject actions, and other attributes Analysis reports in spreadsheet form Basic understanding of MS Office, transportation planning, and safety management
Bicycle Countermeasure Selection System – BIKESAFE Online tool provides practitioners with a process for determining possible engineering, education, and/or enforcement treatments to help mitigate known bicycle crash problems and/or to help achieve a specific performance objective Crash Data: date, time, location, demographics of involved parties, subject actions, and other attributes List of potential countermeasures based on bicycle crash types and performance objectives Basic understanding of transportation planning and safety management
Pedestrian Safety Guide and Countermeasure Selection System – PEDSAFE Online tool provides practitioners with a process for determining possible engineering, education, and/or enforcement treatments to help mitigate a known pedestrian crash problem and/or to help achieve a specific performance objective Crash Data: date, time, location, demographics of involved parties, subject actions, and other attributes List of potential countermeasures based on pedestrian crash types and performance objectives Basic understanding of transportation planning and safety management
Intersection/Interchange Safety Analysis Tools
Interchange Safety Analysis Tool (ISAT) ISAT provides design and safety engineers with an automated tool for assessing the safety effects of geometric design and traffic control features at an existing interchange and adjacent roadway network. ISAT can also be used to predict the safety performance of design alternatives for new interchanges and prior to reconstruction of existing interchanges. Intersection Data: area type (rural/urban), analysis years Crash Data: dates, total number of crashes Roadway Data: length of segment, number of lanes, traffic volume data (ADT), major-road traffic volume (AADT), minor-road traffic volume (AADT) Ramp Characteristics Data: ramp type, ramp configuration (diamond/loop/directional/etc.), ramp traffic volume (AADT) The primary outputs from an analysis include:
  • Number of predicted crashes for entire interchange area
  • Number of predicted crashes by interchange element type
  • Number of predicted crashes by year
  • Number of predicted crashes by collision type
Outputs are reported for three severity levels: total (TOT), fatal and injury (FI), and property-damage only (PDO) crashes.
Basic understanding of geometric design concepts, and working knowledge of MS Excel spreadsheets
Surrogate Safety Assessment Model (SSAM) SSAM is a tool for traffic engineers to perform comparative safety analysis of highway design alternatives using traffic simulation models Detailed vehicle trajectory data exported from traffic simulation software (i.e., AIMSUN, Paramics, TEXAS, VISSIM) Simulated conflict data including: total number of conflicts, number of conflicts by type (i.e., crossing, lane-change, or rear-end events), and conflict severity indicators (e.g., average TTC, PET, Delta-V values) Experience with traffic simulation software and automated traffic conflict analysis

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Page last modified on October 29, 2014.
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