Various research studies in the past have investigated the potential pavement damage of wide-base tires as compared to regular dual-tire assemblies, with many drawing the conclusion that wide-base tires are more damaging to pavements. However, until five years ago, all the research studies documented in the literature were conducted on early generations of wide-base tires, which may or may not have been intended for highway use. The early research results may, in part, account for the lack of wide-base tire adoption in the United States due to inconsistent State restrictions on these tires, which hinder interstate commerce. Recent advances in tire technology have led to the design of wide-base tires that have wider tread than previous designs, resulting in a load distribution more comparable to that of dual tires. Therefore, an evaluation of these new tire designs is needed to determine their contribution to pavement damage and other factors, such as safety and economic impacts, with respect to dual configurations. There is also the issue of the discrepancy between the reported width of the tire and the actual tread width. From an enforcement perspective, it is much easier to read the width of the tire than to measure it. From the pavement's perspective, all that contributes to the damage of the pavement is the width of the tire that it contacts. The United States Environmental Protection Agency (EPA) SmartWay Transport Partnership promotes the use of wide-base tires as a way to improve fuel economy by reducing weight, aerodynamic drag, and rolling resistance. Other potential benefits the EPA SmartWay Transport Partnership cite are reduced driveby noise and improved stability. The Federal Highway Administration (FHWA) and the Asphalt Research Consortium sponsored an international workshop on the use of wide-base tires at the Turner-Fairbank Highway Research Center (TFHRC) on October 25–26, 2007. The outcome of the workshop can be found at http://www.arc.unr.edu/Workshops.html. The research needs identified will support this project. Trucking operation factors that directly affect pavement damage can be classified into three major components: vehicle-generated load, axle and tire configuration transferring the load, and pavement carrying the load. To fully characterize the damage induced by different tire and axle configurations, the effects of vehicle, tire, and pavement and their interaction must be considered. Vehicle and tire factors include axle loads, axle spacing, speed, tire inflation pressure, and tire configurations. Pavement parameters include surface roughness, materials properties, layer thicknesses, and subgrade strength. The recent introduction of the Mechanistic-Empirical Pavement Design Guide (MEPDG) has shifted the emphasis in pavement design from empirical methods to more rational approaches. Therefore, the impact of different vehicle tire factors on the pavement damage needs to be determined using rigorous theoretical modeling capable of simulating field conditions, and should be validated utilizing field test response measurements.
The key project objectives are:
(1) Quantify the impact of vehicle-tire interaction on pavement damage using advanced theoretical modeling validated via full-scale pavement testing. This includes the determination of the relative effects of wide-base tires and dual-tire assemblies on pavement performance. This should also include the determination of the relationship between the reported tire width and aspect ratio, load, inflation pressure, and actual tread width.
(2) Develop a tool and methodology that allows the States to assess the impact of wide-base tires on the pavement network.
(3) Perform an analysis of the economic, safety, and environmental effects of using wide-base tires relative to the impact on pavement performance.