Effect of Wide-Base Super Single Tires on Pavements

1. Connecting South Dakota and the Nation 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

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. Dual/ 275 2000 2002 1980 1982 2000 385 425 445/455 495 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

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 1st 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. Selection of Most Pertinent Studies

9. Tire-PavementContact Area and Stress (Wang and Al-Qadi 2009; 2011)

10. Damage Ratioson Thin & Thick Asphalt Pavement

11. Combined Damage Ratios

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

13. Future Work • Analyze impact on fullrange 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

14. 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

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