FHWA also conducted a national evaluation of the HSIP to estimate expected program results using the project information from the 2017 HSIP reports. The purpose of the evaluation was to estimate a national benefit cost ratio for the HSIP. The HSIP national benefit cost ratio provides an indication of the programs national impact and the benefits the public can expect from investments in the HSIP.
The evaluation methodology makes use of the full project listing information from 49 States plus the District of Columbia (2017 HSIP Project Database) and associated crash modification factors (CMFs) from the CMF Clearinghouse, the Fatality Analysis Reporting System (FARS), the Highway Performance Monitoring System (HPMS), the Highway Safety Information System (HSIS), FHWA, and various reports. California was excluded from the analysis, as many elements needed for the analysis were not available. Puerto Rico was also excluded, given that road improvement project needs and costs deviate from those in the continental U.S. The following steps indicate how to apply the selected methodology for projects in the 2017 HSIP Project Database with complete data:
- Calculate the estimated crash reduction for each project group
- Estimate a "before" crash rate using data from FARS, HPMS, and HSIS.
- Identify appropriate CMFs from the CMF Clearinghouse.
- Calculate the monetary benefit for each project category by converting crash savings to dollar amounts.
- The crash cost values in the 2017 analysis are based on the crash severity values recommended by Harmon et al. in a recent FHWA resource entitled "Crash Costs for Highway Safety Analysis". The values for each combination of crash severities (e.g., K, KA, KAB, etc.) were calculated using information from Council et al and the methodology reported in a memo written by Bhagwant Persaud to FHWA.
- Divide annual monetary benefit by the annualized project cost to calculate the benefit-cost ratio.
- Assume a service life per treatment type using information from the Service Life and Crash Cost User Guide available on the CMF Clearinghouse.
- Calculate a program wide benefit-cost ratio by averaging the ratios from all project groups.
- Weight the average based on HSIP funds spent for a project to account for project groups which were more prevalent in the data.
For this reporting cycle, it was possible to calculate the expected project level benefit cost ratios for 1,194 segment and intersection-based projects, which is approximately 24 percent of the projects listed in the 2017 HSIP Project Database. Table 4 presents the weighted results (based on amount of HSIP funds that were spent for that project). Many projects had a range of years for the assumed service life, so the table presents the BC ratio according to the minimum and maximum service lives.
The values in the bottom row of Table 4 (ranging from 6.09 to 11.24) represent the range of BC ratios for the HSIP program for segment and intersection-based improvement projects, depending on the minimum or maximum service life of the treatment and discount rate. Comparatively, the range for the 2016 HSIP project listing was 4.36 to 6.51.
Table 4. Weighted BC Ratio for Segment and Intersection Based Projects (weight based on total project cost)
|Weighted BC Ratio (min Service Life, 3% discount rate)||Weighted BC Ratio (max Service Life, 3% discount rate)||Weighted BC Ratio (min Service Life, 7% discount rate)||Weighted BC Ratio (max Service Life, 7% discount rate)|
|869 Segment Based HSIP Projects (weighted on segment project cost)||
|325 Intersection Based HSIP Projects (weighted on intersection project cost)||6.73||7.60||5.00||5.47|
|1,194 Segment & Intersection Based HSIP Projects (weighted on segment & intersection project cost)||7.71||11.24||6.09||8.04|
Many projects could not be included in analysis because they were either missing key data elements (e.g., number of miles or intersections treated, CMF, project cost, etc.) or were non-infrastructure projects. The calculated benefit-cost ratio for each of the 1,194 projects relied heavily on assumptions for each project regarding the applicable CMF, service life, crash rate, and injury severity cost.