Macrotexture Model Development for Asphalt Mixtures Aimed at Safety Analysis [techbrief]

The Safe System Approach, the guiding paradigm of the United States Department of Transportation National Road Safety Strategy, recognizes that system redundancy is crucial to reducing deaths and serious injuries on our Nation’s roads. Where pavements are concerned, this paradigm involves providing adequate levels of friction supply to meet the friction demand (i.e., the level of friction needed to perform braking, steering, and acceleration maneuvers safely) of a given road type and context. Two pavement surface characteristics, microtexture and macrotexture, are the primary factors that influence the pavement friction. Microtexture contributes to traction at the pavement–tire interface at all traffic speeds. While also contributing to traction at all traffic speeds, macrotexture is more critical at high speeds. Macrotexture influences the hysteresis, or energy lost due to the rubber deformation component of friction and facilitates drainage at the pavement–tire interface, so macrotexture is particularly critical during conditions when water is present on the pavement, such as during adverse weather.