Benefit-Cost Analysis of Florida High-Friction Surface Treatments
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This presentation was prepared for the 95th Transportation Research Board (TRB) Annual Meeting, January 2016. Contributing to the presentation: Bryan Wilson, Brad Brimley, Jun Zhang, Anol Mukhopadhyay of Texas A&M Transportation Institute; Jim Mills of Pavement Analytics, LLC; and Charles Holzschuher of Florida Department of Transportation.
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Benefit-Cost Analysis of Florida High-Friction Surface Treatments
- 1. Benefit-Cost Analysis of Florida High-Friction Surface Treatments Bryan Wilson ,Brad Brimley, Jun Zhang, Anol Mukhopadhyay Texas A&M Transportation Institute Jim Mills Pavement Analytics, LLC Charles Holzschuher Florida Department of Transportation TRB 95th Annual Meeting January 11, 2016Pavement Analytics, LLC
- 2. High-Friction Surface Treatments • Reduces horizontal curve road departures • Maintenance treatment for bridge decks • Polish resistant aggregate in polymer resin binder
- 3. HFST Crash Reduction Effectiveness HFST > Roadway geometry correction (time intensive, costly)
- 4. Our Research Objectives • Evaluate the crash rates on different roadway section types before and after HFST construction. • Compare benefit-cost ratios of different HFST applications. Scope • Identify all HFST projects in Florida. • Collect project data and before/after crash histories. • Calculate benefit-cost ratios by section type.
- 5. Procedures
- 6. Data Collection • Project location • Contract and bidding documents • Roadway geometry • Traffic characteristics • Construction duration • Crash statistics
- 7. Crash data • 5-yrs before HFST, and after HFST up to present • Exclude crashes outside HFST limits • Exclude crashes during construction period • KABCO coding • Crash rate: 𝐶𝑟𝑎𝑠ℎ 𝑝𝑒𝑟 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑣𝑒ℎ𝑖𝑐𝑙𝑒𝑠 = 𝐶𝑟𝑎𝑠ℎ𝑒𝑠 𝑦𝑒𝑎𝑟 𝐴𝐴𝐷𝑇 ∗ 365 ∗ 1,000,000
- 8. Data Analysis • HFST Section Cost • Actual project cost • Normalized project cost 𝐶𝑜𝑠𝑡 $ = 𝐴𝑣𝑔. 𝑈𝑛𝑖𝑡 𝐻𝐹𝑆𝑇 𝐶𝑜𝑠𝑡 $ 𝑦𝑑2 × 𝐴𝑟𝑒𝑎 𝑦𝑑2 • Bid unit HFST cost • Comprehensive unit HFST cost
- 9. Data Analysis • Benefit Calculation (3 methods) • Total Crashes by KABCO (FDOT version) • Total Crashes by average crash cost ($195,000) • Wet Weather by average crash cost ($195,000) • Benefit-Cost per section type 𝐵𝐶 𝑟𝑎𝑡𝑖𝑜 = 𝑖 𝑛 [𝐵𝑒𝑛𝑒𝑓𝑖𝑡($)𝑖 𝐶𝑜𝑠𝑡($)𝑖] 𝑛 Cost Type Cost Per Crash By Type (Thousands $) K A B C O Lost Quality of Life $7,750 $919 $252 $108 $31.8 Economic $1,400 $82.0 $23.7 $19.5 $10.4 Societal Impact (Total Cost) $9,140 $1,001 $276 $128 $42.3 FDOT Societal Impact (Total Cost) $10,000 $819 $163 $100 $6.50
- 10. Results
- 11. Project Data • 23 total HFST projects • Mainline and bridge deck applications • 47 unique HFST sections • 38 sections w/ data • 16 tight curves • 16 wide curves/tangents • 6 intersections/ intersection approaches Mainline (Dev 333) Bridge deck (TSP 403)
- 12. Radius
- 13. Section Length
- 14. Traffic Volume
- 17. Crash Rates (Total Crashes)
- 18. Crash Rates (Wet Weather Crashes)
- 19. Change in Crash Rate
- 20. HFST Unit Cost
- 21. Normalized HFST Project Cost
- 22. Benefit-Cost
- 23. Benefit-Cost
- 24. Conclusion
- 25. Findings Summary Crash reduction with HFST • Most effective on tight curves: • Average 32% reduction of total crashes. • Average 75% reduction of wet weather crashes. • Wide curves / tangents: • No crash history = no change in crash rate. • Intersections/intersection approaches: • Effectiveness undetermined. • In some cases, total crashes were reduced (41%) • and increased in others (151%).
- 26. Findings Summary HFST Cost • Average bid unit cost: $34/yd2. • Average comprehensive unit cost: $59/yd2 • Average normalized HFST project costs: • Tight curves - $172,000 • Wide curves / tangents - $560,000 • Intersections / int. approaches - $476,000
- 27. Findings Summary Benefit-Cost Ratios (crash reduction perspective) • Most cost-effective on tight curves: • 24.5 for total crashes (KABCO weighting). • 26.0 for total crashes (avg. weighting). • 18.0 for wet weather crashes (avg. weighting). • Individual projects with HIGH ratios of 118, 65, 56, and 30. • Wide curves / tangents: • No benefit on average. • Intersections / intersection approaches: • Avg. benefit-cost ratio undetermined. • Positive B-C ratio in some cases (50, 33, 20) • Negative B-C ratio in other cases (-66, -32, -23)
- 28. Recommendations • Continue promoting HFST for crash reduction around tight curves with a history of crashes. • Reduce emphasis of safety benefits when considering HFST on wide curve/tangent sections that have no history of crashes. • Evaluate benefit-cost of HFST as a maintenance treatment of concrete bridge decks. • Evaluate in-detail the nature of crashes at intersection/ intersection approach sections and how the crashes may relate to the installation of HFST.
- 29. Thank You. Questions? Bryan Wilson b-wilson@tti.tamu.edu Pavement Analytics, LLC
Editor's Notes
- Kentucky – 129 section total NCHRP 617 – Crash modification factors Wisconsin – 5 locations Michigan – 4 sites Where do HFSTs provide the most value from a safety perspective? There are multiple points that should be considered about the above findings: -The crash reduction performance of HFST may be artificially inflated compared to other pavement treatments. This is because HFST is usually applied to high problem locations while other treatments are placed on a wide range of surfaces. While crash reduction on these problem scenarios is clearly apparent, other treatments may have also reduced crashes in a comparable scenario. -Another consideration is that HFST can only be effective where surface friction demand is originally insufficient. The affected crashes are typically wet-weather roadway departures around horizontal curves and highway loops. Other types of crashes (distracted/drunk driving, side swipe/head on, etc.) will be largely unaffected by an HFST installation. -One final note is that many publications discuss HFST crash reductions for a limited set of HFST sections. They highlight the best performers and present a skewed perspective.
- Advanced procedures for processing crash data (e.g., normalizing against control sections, identifying and filtering individual crashes based on crash conditions, etc.) was outside the scope of this project. Normalizing against control sections is particularly difficult when many of the sections of concern are outliers.
- Actual project cost? No data for some projects….extra work done….different years of construction. Bid unit….is not the full cost of HFST installation.
- K − Fatality, A − Incapacitating injury, B − Non-incapacitating injury, C − Possible injury, and O − Property damage only. NHTSA - National highway traffic safety administration
- Comprehensive: All costs of construction (traffic control, repairs, striping, etc.) The HFST unit costs and estimated section costs (based on total project data) are shown in Table 2. The unit cost of 7 projects could not be determined because they were bid lump-sum, and total project costs were not available for 18 projects. Aside from unusually low and high unit cost bids in 2011, the range of HFST bid unit costs was from $26 to $40/yd2, while the range of total HFST unit costs (including all related construction costs) was from $36 to $112/yd2. An average total unit cost of $59 was used for all projects in this analysis.