1. Prevention benefits were assigned to each type of crash (K, A, and B). These values were obtained from the TxDOT 2021 SII Calculator. 2. A crash rate per 100,000 roadway users was calculated for each type of crash from the number of crashes between 2019 and 2023 by using the number of crashes between 2019 and 2023 and dividing by the number of roadway users between 2019 and 2023 (Before Crashes/AADT/365/5) and then multiplied by 100,000. 3. The crash rate was then multiplied by the crash modification factor factors for applied countermeasures. 4. The new crash rate was then converted to crashes prevented in the build year (assumed 2025) with the following formula: ((Before Crashes Per 100,000 Users - Crashes Modified by CMF Applicable CMF Per 100,000 Users) * 2025 AADT * 365 / 100,000). 5. The crashes were then multiplied by their prevention benefit values to obtain a benefit value per year. 6. A benefit growth rate was then obtained by multiplying the inflation rate (assumed 3%) by the growth rate. 7. A present benefit value was then calculated by the annuity to present value formula. 8. Annual maintenance costs were calculated using the TxDOT HSIP. 9. For countermeasures with service lives less than 20 years, it was assumed that the full countermeasure installation cost would be incurred each time the service life expired (e.g. paint has a service life of 4 years, and it was assumed that the paint would be reinstalled each 4 years, for a total of 5 times in 20 years). Note that for countermeasures that are hard infrastructure and not in the HSIP, such as curb extensions, a service life of 25 years was assumed. It was further assumed that these costs would be evenly spread over the 20-year lifecycle to obtain an annual reinstallation cost. 10. The annual reinstallation cost was then added to the annual maintenance cost from the HSIP for each countermeasure to obtain a final annual maintenance cost. 11. A present annual maintenance cost was then calculated by the annuity to present value formula. 12. The present annual maintenance cost was added to the installation cost to obtain a present cost value. 13. The benefit/cost ratio was then obtained by dividing the present benefit value by the present cost value.
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