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Data-Driven Safety Analysis (DDSA)

Through predictive and systemic analysis, PennDOT analyzes data to target safety improvements.

analysis venn diagram

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 alternatives. 

How Does It Work?

The data-driven approaches of predictive and systemic analysis can be implemented individually or in combination.

Predictive analysis combines roadway inventory, traffic volume and crash data to provide more reliable estimates of an existing or proposed roadway’s expected safety performance. The data helps agencies make better decisions and informs the public about the safety benefits they can expect from the investment. The Highway Safety Manual, published in 2010, provides many quantitative ways to perform predictive analysis.

Systemic analysis combines crash and roadway data to identify high-risk roadway features that correlate with certain crash types. Agencies have traditionally relied on crash history data to identify “hot spots,” or sites with high crash frequency. 

Systemic analysis identifies locations that are at risk for severe crashes, even if there is not a high crash frequency. Practitioners can then apply low-cost countermeasures to those locations. The benefit is wider, more targeted safety investments.

What Are The Benefits?

  • Allows for informed decision making. Predictive and systemic analysis improves on traditional decision-making approaches that rely on subjective and limited quantitative measures of safety performance.
  • Targeted investment. PennDOT can use the analysis to optimize funding through targeted safety improvements. 
  • Improves safety. PennDOT can use comprehensive data to allocate resources that result in fewer fatal and serious injury crashes.

Case Study

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.

More Information

For more information about this innovation, contact the STIC Management Team.