Alternatives Safety Analysis Summary: 2035 

Rank Alternative Total Crashes Crashes Reduced Total Cost of Crashes Potential Reduction 

1 P 820.8 87.3 $22,060,778 $2,345,187 

2 J 828.2 79.9 $22,257,509 $2,148,456 

3 Q 851.6 56.5 $22,887,479 $1,518,486 

4 B/O 902.9 5.2 $24,278,285 $138,680 

5 No Build 908.1 0.0 $24,405,965 0 

(Source: LADOTD) 

Data-Driven 

Safety Analysis

PROJECT CASE STUDY

Louisiana Integrates Quantified Safety Performance into Design 

Decision on New Highway 

The Louisiana Department of Transportation and Development (LADOTD) is constructing a high-speed, fourlane, rural arterial highway between Interstate 12 and State Route 21 in Bush, Louisiana, to address regional 

transportation mobility needs and potentially stimulate economic growth and activity in Washington and St. 

Tammany Parishes. This project will replace an existing two-lane, undivided highway with numerous access 

points in order to alleviate congestion, shorten travel time and improve safety. 

LADOTD applied predictive safety analysis to quantify safety performance when comparing proposed 

alternatives (including the No Build alternative) during the project’s engineering and design phase. 

PREDICTIVE SAFETY ANALYSIS 

BENEFITS

Improved Safety

Predictive analysis considers the 

safety implications of each design 

configuration, providing differentiation 

between alternatives.

Informed Decision-Making

Predictive analysis helps quantify 

the safety impacts of transportation 

decisions, allowing safety to be purposely 

considered along with other project 

goals.

Optimized Investment

Safety performance can be quantified 

in terms of the number and severity of 

crashes, which can then be translated 

into societal costs over the life of the 

project.

Safety Tools and Best Practices Used

LADOTD applied the Federal Highway Administration (FHWA) 

Interactive Highway Safety Design Model (IHSDM) crash 

prediction module. They used the module, which implements 

the American Association of State Highway and Transportation 

Officials (AASHTO) Highway Safety Manual (HSM) predictive 

methods, to predict the number of crashes for each alternative 

in the design year of 2035. The analysis quantified the safety 

performance of each alternative in terms of the predicted 

number of crashes by severity and their associated societal costs 

over the life of the project. 

Using the No Build alternative as a benchmark, the project team 

used the number of crashes predicted by IHSDM to compare the 

alternatives. The team disaggregated the predicted crashes into 

severity levels and converted them into a dollar value using cost 

data from the National Highway Traffic Safety Administration’s 

technical report, The Economic Impact of Motor Vehicle Crashes 

(2000), and updated the data with the Consumer Price Index. This 

allowed them to evaluate the monetary differences realized by 

the potential crash reductions. 
All four alignments were designed to the same criteria, 

but their unique characteristics had meaningful 

differences in their predicted safety performance. 

The highest ranked alternative in terms of safety 

performance predicted roughly 10 percent fewer 

crashes than the No Build alternative, resulting in a 

projected $2.3 million cost savings to society.

Key Takeaway

` Predictive safety analysis allows safety to 

be measured similarly to other criteria in a 

preferred alternative. The goal is to have 

safety considered, not to trump or dictate 

the decision.

Preferred Alternative

The U.S. Army Corps of Engineers issued the Record of Decision in June 2012 for the alternative they determined 

to be the most environmentally acceptable while achieving project purpose and need. In making the 

selection, the Corps assessed costs and benefits and considered public and agency comments developed 

as part of the Environmental Impact Statement process. They considered safety as part of the traffic and 

transportation impacts when assessing each alternative’s potential physical, natural and social environmental 

consequences. While the selected alternative did not have the highest predicted safety performance, it is still 

expected to experience fewer crashes and result in less societal cost expended than the No Build alternative. 

Selecting an alternative with a substantial reduction in crashes, but not the greatest reduction, is an exercise in 

sound engineering judgment. The more important aspect is that the decision-makers selected an alternative 

based on consideration of all impacts, including safety.

Conclusions

Agencies responsible for executing National Environmental Policy Act requirements and selecting the preferred 

alternative make such decisions by balancing many impacts and trade-offs. An agency is not compelled to 

select the alternative believed to be the safest, just as it is not compelled to select the lowest-cost alternative or 

the alternative that has the least impact on a particular environmental asset, such as wetlands.

On this project, the team applied substantive safety data to the environmental process and alternative analysis. 

This marked a transition from the nominal safety approach to using quantified safety performance to make 

project decisions. All of the alternatives included a raised median with limited access points, thereby improving 

safety. However, applying substantive safety analysis by alternative allowed the team to use safety as a 

differentiating feature in the evaluation and selection process.

ADDITIONAL RESOURCES

` This document contains information presented in “Safety in the Project Development Process: A Context 

Sensitive Approach,” a case study provided courtesy of the Institute of Transportation Engineers: www.ite.org

` Additional information on LADOTD highway safety methods and tools can be found at 

http://www.dotd.la.gov/planning/highway_safety/

` More information on Data-Driven Safety Analysis is available on the Every Day Counts website at 

http://www.fhwa.dot.gov/everydaycounts/edc-3/analysis.cfm

For additional information 

about this EDC initiative, 

please contact:

Jerry Roche

FHWA Office of Safety

515-233-7323

Jerry.Roche@dot.gov

John McFadden

FHWA Resource Center 

410-962-0982

John.Mcfadden@dot.gov

FHWA-14-CAI-055

www.fhwa.dot.gov/everydaycounts