1. Effect of Wide-Base Super Single Tires on Pavements David Huft, SDDOT Research Program Manager AASHTO Research Advisory Committee Meeting Madison, WI July 22, 2014 Connecting South Dakota and the Nation

2. SD2012-01 Effect of Wide-Base Super-Single Tires on Pavements Suggested by SD Trucking Association Hoped to lift 500 lb/in restriction on 445/455 mm tires 5-month project Work by Hao Wang From Priest & Trimm, TRR 1949

3. Wide-Base Tire Characteristics Introduced to North America in 1982 to replace dual tires Design for high-speed long-distance carrier Reduced fuel consumption Reduced tire recycling Increased payload Better ride comfort and vehicle handling 19801982 2000 2002 2000 385425445/455495 Dual/ 275

4. Early & Recent Wide-Base Tires Early Generation 385/65R22.5, 425/65R22.5) High inflation pressure (790-890kPa) Small contact area High contact stress High damage ratios 1.5-2.0 for rutting 2.0-4.0 for fatigue cracking New Generation 445/50R22.5, 455/55R22.5 New crown architecture 15-18% wider than 1 st gen Reduced tire pressure Damage ratios vary by: pavement structure damage type climate condition (Virginia Smart Road 2000; Europe COST334 2001; Canada 2004; NCAT 2006; ILDOT 2008; FLDOT 2010)

5. Problem Statement In South Dakota, wide-base tires may be generally substituted for standard duals, but the legally allowed weight on single axles is reduced 17,500 lb for 445mm tires, 18,000 lb for 455 mm tires 20,000 lb for dual-tire configurations Previous studies involving laboratory tests, field tests, and modeling have generated mixed results It was unclear whether results are applicable to the full range of road surfaces (including unpaved) that exist on state and local highways in South Dakota

6. Objectives Based on others’ research, assess effects of allowing 20,000 pound loads on single axles equipped with 445mm and 455mm wide-base tires on state and local roads in South Dakota Assess need for additional research involving physical testing or modeling

7. Major Research Tasks Extensive Literature Review State Survey and Interview Select Most Pertinent Studies Calculate Damage Ratios Assess Impact of Policy Change Assess Additional Research Needs

8. Web Survey and Interviews Created using Zoomerang through SDDOT Research Survey state DOTs for load regulation or permit fee of wide- base tires (22 responses) Survey state trucking associations for use percentage, trend, and benefits of wide-base tires (8 responses) Discussion with SDDOT staff to characterize road surface designs in SD Interview local truck owners and operators through conference call (6 companies)

9. Survey Results from State DOTs Tire load limit (pounds/inch) No limit500550-560600650700 Number of responses (out of 22) 933412 Allowable single axle load Same for wide-base tires and dual tires Smaller for wide-base tires Number of responses (out of 20) 155 Allowable tandem axle load Same for wide-base tires and dual tires Smaller for wide-base tires Number of responses (out of 20) 182

10. Types of wide-base tires in use 385mm and 425mm 445mm and 455mm Not allowed for use Number of responses (out of 8) 67NA Estimated Percentage of wide-base tires 0-5%6-10%11-15%16-20% Number of responses (out of 8) 3302 Trend of using wide- base tires Gradually increasing Staying about the same Gradually decreasing Rapidly decreasing Number of responses (out of 8) 5210 Results from Trucking Associations

11. Spread Tandem in South Dakota AverageStandard DeviationMinimumMaximum Total Trucks9438981288827933 % over 8'27%5%19%35% % over 10'18%5%11%26% Average Axle Spacing (ft) 5.80.45.36.7 Spread tandem (axle spacing greater than 10 feet in tandem axles) is used by many trucking companies in South Dakota Truck data from 13 WIM sites (average per month)

12. Literature Review U.S., Canada, Europe Old and new wide-base tires Field testing APT vs Field Single vs. Tandem Modeling Multilayer Elastic vs. Advanced Finite Element Modeling Assumptions on Contact Stress and Area Stationary vs. Moving load Various Pavement designs Impact of new wide-base tires on pavement damage depends on pavement structure and predominant failure mechanism Bottom-up fatigue cracking ↑ Subgrade rutting potential ↑ Primary rutting potential ↑↓ Near-surface cracking potential in thick asphalt pavements ↓

13. Selection of Most Pertinent Studies Studies on wide-base tires Similar Pavement Design in South Dakota Quebec Ministry of Transportation (Pascale et al. 2004) TonS (Thin on Strong: 2 to 5 in. ACP on > 8 in. granular base) UTC/Nextrans Study (Al-Qadi and Wang 2010; Wang and Al-Qadi 2011) NCAT Study (Priest and Timm, 2006) THK (Thick: 5 to 10 in. ACP w/ granular base) Ontario Ministry of Transportation (Ponniah et al. 2006) Florida DOT Study (Greene et al. 2010) Illinois DOT Study (Al-Qadi and Wang 2009) FD (full-depth: > 10 in. ACP w/no granular base)

14. Tire-Pavement Contact Area and Stress (Wang and Al-Qadi 2009; 2011)

15. Critical Pavement Response Transfer Function !

16. Damage Ratios

17. Damage Ratios on Thin & Thick Asphalt Pavement DistressThin AsphaltThick Asphalt Fatigue Cracking1.68-2.82 0.86-1.26 Top-Down Cracking N/A 0.16-0.67 Primary Rutting1.35-1.771.05-1.27* Subgrade Rutting 1.31-2.35N/A References Wang and Al-Qadi, 2011 Pascale et al. 2004 Greene et al. 2010 Ponniah et al. 2006

18. Combined Damage Ratios Pavement Type Wide-base 455 vs. Dual tires Wide-base 445 vs. Dual tires RangeAverageRangeAverage Full-depth (FD)0.85-1.321.08NA Thick asphalt (THK) 0.69-1.070.880.76-1.411.08 Thin asphalt on strong base (TonS) 1.45-2.311.88NA

19. Damage Ratios on State Highway Network CodeType ACBase % of Total System Miles Damage Ratio Weighted Damage Ratio FDFull Depth>10”no2.3%1.080.025 THKThick5-10”yes33.5%0.880.295 TonS Thin on Strong 2-5”> 8”24.7%1.880.464 TonW Thin on Weak 2-5”< 8”7.1%1.88*0.133 AonCAC on PCCPyesPCC8.1%1.0**0.081 BLOT Bituminous surface treatment 0.7%1.88*0.013 PCCPCC Pavements21.6% 1.0** 0.216 Total100%1.228

20. SB154: Allows 445/455 mm Tires on Major SD Highways and “any locally designated highway within the corporate limits of any municipality adjacent to the Interstate highway system”

21. Future Work Analyze impact on full range of road surfaces (including unpaved) in SD Quantify possible increase of life-cycle agency cost by allowing equal load limit on wide- base single tires and dual tires on other state and local roads Consider three important contributing factors to pavement damage ignored in previous studies: unbalanced loads between dual tires, wheelpath wandering, and dynamic loading

22. Keys to Project Success Active support of SD trucking industry Political urgency Multi-disciplinary technical panel Relevant research by done others Availability of experienced researcher

23. Questions? Please contact David Huft SDDOT Research Program Manager 605.773.3358 dave.huft@state.sd.us