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Modeling the Impact of Pavement Roughness on Bicycle Ride Quality

Many cities and states rely on aggregate seal coats (chip seals) to maintain roads. Chip seals are economical as a surface for lower-volume roads or for preservation treatments on asphalt roads, and the technology for increasing the life span of chip seals is continually improving. Chip seals often have higher macrotexture than do asphalt or concrete surfaces, which provides high skid resistance for motor vehicles. However, bicycling has increased in many parts of the country, for both recreation and commuting, and the high macrotexture of chip seals has led bicyclists to protest that the use of chip seals has decreased the comfort of recreational bicycle rides. In California, recreational bicyclists have contacted the California Department of Transportation (Caltrans) regarding the texture of chip seals on popular bicycling routes. Caltrans sponsored research to measure pavement surface macrotexture and roughness, to conduct bicycle ride quality surveys in partnership with six California bicycling clubs, and to do preliminary modeling. These data have been used to develop further a multilevel binomial regression model that indicated that surface macrotexture and roughness have a strong impact on perceived bicycle comfort levels. The model could be used to develop design guidelines for urban and rural bicycle routes.