Safety Analysis Methods & Resources


Based on Historic Crashes and Trends

Location Specific Analysis

Specific location safety analysis determined by:

  • Where there is a high number of crashes
  • Where there are high crash rates
  • Where there are fatalities/serious injuries
  • Where systemic analysis has identified as a location of focus
  • Conducting crash report analysis

Systemic Analysis

Broader network analysis of data to determine where safety improvements are needed:

  • Identifies characteristics that frequently contribute to certain crash types
  • Focuses on countermeasures that can be deployed widely across the system
  • Identifies and prioritizes locations across the network for implementation

 

Based on Safety Performance

Predictive Analysis

Risk based approach to systemically analyze safety performance of roadways:

  • Uses risk factors to identify locations to implement safety improvements to prevent crashes
  • Safety Performance Functions (SPFS) are developed from crash data from similar sites, all adjusted to presumed "base" conditions
  • Crash Modification Factors (CMFs) are then applied to convert from the base conditions to the conditions at the location being studied
  • A local calibration factor is also applied based on local crash experience on similar roadway sites
  • Empirical methods may also be applied if both a SPF and actual crash data are available
  • Crash Reduction Factors (CRFs) and relationship to CMFs

Click here to access Safety Data Analysis and Mapping tools.

data analysis

 

HSM

AASHTO’s Highway Safety Manual (HSM) is the guidance document for incorporating quantitative safety analysis in the highway transportation project planning and development processes to inform the highway transportation decision-making process. 

The HSM includes guidance on:

  • Human factors and the fundamentals of traffic safety
  • The roadway safety management process (including information relevant to FHWA’s Highway Safety Improvement Program requirements and project planning), including:
    • Network screening (identify sites with potential for crash or severity reduction
    • Site assessment (diagnosis, countermeasure selection, economic appraisal
    • Project prioritization
    • Safety effectiveness evaluation
  • Predictive methods for infrastructure improvement project alternative analysis and development/design, including:
    • Use of national safety performance functions (models) developed to predict crashes by severity specific facility types and base conditions
    • Associated crash modification factors (CMFs) to estimate the potential effects of design alternatives or changes from base conditions

FDOT HSM Resources & Tools

HSM Part B: Roadway Safety Management Process

FDOT Network Screening

Network screening resources on this page include:

 

  • Safe Strides 2 Zero (SS2Z) – conducting an annual
    screening of signalized intersections on the SHS. 
    Identifies high crash signalized intersections and is
    shown in the Safety Needs List Dashboard. 
  • 2020 Pedestrian & Bicycle Network Screening –
    a risk-based evaluation of pedestrian and bicycle safety
    on the SHS utilizing roadway characteristics and ped and
    bike demand characteristics. Results are available on eTraffic.
Safety Management Process

FDOT Safety Needs List Dashboard

The Safety Needs List Dashboard enables FDOT project scoping staff to incorporate safety needs into any work program project. The Dashboard consists of the Traffic Operations' Statewide Safety Initiatives and the over-lapping safety needs priorities identified by each district.

HSM Part C: Predictive Method

The HSM Part C provides a predictive method for estimating expected average crash frequencies at individual sites. This method relies on safety performance functions (SPF) that estimate predicted average crash frequency as a function of traffic volume and roadway characteristics (e.g., number of lanes, median type, intersection control, number of approach legs).

FDOT Intersection Control Evaluation (ICE)

The ICE process quantitatively evaluates several intersection control scenarios (alternatives) and ranks these alternatives based on their operational and safety performance. Implementing a “performance-based” procedure such as ICE creates a transparent and consistent approach to consider intersection alternatives based on metrics such as safety, operations, cost, and social, environmental, and economic impacts. ICE resources on this page include:

• Manual on Intersection Control Evaluation
• ICE Forms
• Capacity Analysis at Junctions (CAP-X)
• Safety Performance for ICE (SPICE)

• FDOT ICE Tool

FDOT HSM Spreadsheet Tools & Crash Cost Calculations

• Chapter 10: Rural Two-Lane Roads 750-020-21a
• For data collection, use MUTS Forms 750-020-05a to 750-020-05h
• Chapter 11: Rural Multilane Highways 750-020-21b
• For data collection, use MUTS Forms 750-020-05a to 750-020-05h
• Chapter 12: Urban and Suburban Arterials (2-5 lanes) 750-020-21c
• For data collection, use MUTS Forms 750-020-05a to 750-020-05h
• NCHRP 17-58: Urban and Suburban Arterials (6+ lanes and one-way) 750-020-21d
• For data collection, use MUTS Forms 750-020-05l to 750-020-05n
• Chapters 18-19: Freeways, Interchange Ramps, and Interchange Ramp Terminals

• For data collection, use MUTS Forms 750-020-06a to 750-020-06c

 

Work Under Development

Project Safety Analysis - Initiating the development of Florida based Safety Performance Functions (SPFs) and Crash Modification Factors (CMFs) for intersections in context classifications C3R, C3C and C4. 

Safe System Intersection (SSI) Analysis - Initiating the development of a process to use the SSI index for crash prediction. 

Crash Modification Factors

 

CMF

Crash Modification Factors (CMFs) quantify the expected change in average crash frequency as a result of geometric or operational modifications to a site that differs from set base conditions. The Crash Modification Factor Clearinghouse currently houses over 3,500 CMFs.

Crash Modification Factor Clearinghouse

How to Use Crash Modification Factors

The CMFs that meet the HSM inclusion criteria are identified as such in the Clearinghouse. Many state DOTs have developed a listing of the preferred CMFs for use on projects within their jurisdiction. Several state examples are provided in the Clearinghouse, but users should contact the DOT safety engineer for guidance on appropriate CMFs for use on projects in their jurisdiction.

FDOT HSM Training

The following training modules are made available from the FDOT Design Office.

HSM Webinar 1  - Introduction to HSM & Fundamentals

HSM Webinar 2  - Roadway Network Screening

HSM Webinar 3 - Crash Modification Factors (CMF)

HSM Webinar 4 - Two Lane Rural

HSM Webinar 5 - Multi-Lane Rural

HSM Webinar 6 - Urban and Suburban

HSM Webinar 7 - Freeways

HSM Webinar 8 - Ramps

HSM Webinar 9 - Benefit/Cost Analysis

Other HSM Resources

FDOT Highway Safety Manual User Guide 2015

Highway Safety Manual - Homepage (AASHTO)

HSM Tools (AASHTO)

HSM Data Needs Guide (TRB)

Interactive Highway Safety Design Model (IHSDM) (FHWA)

 

Thank you to FDOT District One for portions of this page content, adapted from the Safety Academy.

Page updated : May 23,2022