Roadside Alligators and the UMTRI Tire Debris Survey

Roadside alligators (also known as tire debris) are those unsightly shreds or fragments of rubber occasionally found on the nation's highways. The typical road user misunderstands the nature, extent, and contributing factors precipitating their formation. During the summer of 2007, the University of Michigan Transportation Research Institute conducted a national tire debris survey that involved the collection of 85,000 pounds of rubber and that provided 300 casings and 1,196 debris items for subsequent failure analysis. This paper discusses tire debris within the context of roadside litter, presents the tire debris survey methodology, and discusses the survey results. Overall, where the original equipment tread or retread status could be determined, original equipment accounted for 60%, and retreads accounted for 40% of the tire casings tested. For tire fragments, the status was 21% (original equipment) and 79% (retread). There was also a strong similarity for these same tire items in the ranking of probable causes of damage or failure. Road hazard or maintenance and operational factors were two of the top three probable causes of damage or failure. This result suggests that the majority of tire debris items found on the nation's highways is not a result of manufacturing or process deficiencies. However, two primary challenges remain: first, increasing public awareness about the origins, characteristics, and impacts of tire debris and, second, ensuring adherence to the highest standards in commercial driver truck operations and associated tire maintenance. Resolving these challenges can significantly reduce roadside tire debris and correct the understanding of highway users about the origins of the roadside alligator.