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    Data-Driven Safety Analysis (DDSA)

    Through predictive and systemic analysis, PennDOT analyzes data to target safety improvements. Data-Driven Safety Analysis (DDSA) allows PennDOT to combine crash and roadway data to identify sites with the greatest potential for improvement and quantify the impact of different improvement alternatives. DDSA is a Federal Highway Administration (FHWA) Every Day Counts Rounds 3 and 4 (EDC-3 and EDC-4) innovation that Pennsylvania championed. 

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    Open roadway with grass and tall trees in either side with blue skies

    How Does It Work? 

    Traditional crash and roadway analysis methods mostly rely on subjective measures of safety performance, making it difficult to calculate safety impacts alongside other criteria when planning projects. DDSA employs newer, evidence-based models that provide state and local agencies with the means to quantify safety impacts.  

    The data-driven approaches of predictive and systemic analysis can be implemented individually or in combination. Predictive analysis combines crash, roadway inventory and traffic volume data to provide more reliable estimates of an existing or proposed roadway’s expected safety performance. It helps identify roadway locations with the greatest potential for improvement and quantify the expected safety performance of different improvement alternatives. Systemic analysis combines crash and roadway data to identify high-risk roadway features that correlate with crash types. It identifies locations that are at risk for severe crashes, even if there is not a high crash frequency.  

    Venn diagram with the words safer roads in the middle and the words predictive analysis on the left and the words systemic analysis on the right

    What Are The Benefits? 

    DDSA allows for more informed decision-making than traditional decision-making approaches that rely on subjective and limited quantitative measures of safety performance. It helps optimize funding through targeted safety improvements in locations that could see huge benefits. DDSA improves safety by using comprehensive data to allocate resources that result in fewer fatal and serious injury crashes.  

    In Pennsylvania, DDSA is used to select and prioritize safety projects based on available data, such as crash history. Safety improvement projects are evaluated in Pennsylvania by PennDOT’s Highway Safety and Traffic Operations Division (HSTOD). Between 2011 and 2017, HSTOD evaluated six network-wide implementations of safety projects for a benefit/cost analysis. In every case, the benefits highly outranked the cost (see chart below). This fact supports that using DDSA to make informed decisions based on performance improves safety and optimizes funding.

    ​Safety Improvement

    Edgeline Rumble Strips (2012)
    		​Centerline Rumble Strips (2014)
    		​Centerline & Edgeline Rumble Strips 
    (2011)
    		​High Friction Surface Treatment (2017)
    		​High Tension Cable Median Barrier (2014)
    		​Intersection Warning Treatments (2012)

    ​Benefit/Cost Ratio

    ​125:1
    		​162:1
    		​117:1
    		​20:1
    		​30:1
    		​28:1

    *Date in parenthesis indicates the year the safety improvement was evaluated.

    Innovation in Motion

    One predictive analysis tool included in FHWA’s DDSA Toolbox is the AASHTO Highway Safety Manual (HSM). The HSM introduces a mathematical- and science-based, technical approach that takes the guesswork out of safety analysis. The manual provides tools to conduct quantitative safety analyses, allowing for safety to be evaluated alongside other transportation performance measures. Since PennDOT began widely using the HSM in 2016, safety projects have been more efficiently and effectively implemented. By applying these contemporary road safety management methods, PennDOT maximizes the investment of safety improvements.