Better Roads

October 2013

Better Roads Digital Magazine

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RoadScience Photo courtesy of Tom Kuennen by Tom Kuennen, Contributing Editor On S.H. 130, Central Texas Toll Road, Roadtec MTVs (Shuttle Buggies) feed pavers with skis with sensors providing input for automatic-leveling controls. Smooth Going How new technology is changing in the quest for smooth pavements S urveys consistently show that smoothness is the No. 1 criterion by which road users judge pavements. Other studies have found pavements that are built smooth stay smoother longer and provide a longer life. This makes it appear that pursuing smoothness from the start is a cost-effective proposition. State Departments of Transportation (DOTs) routinely employ smoothness specifications in their regulations and are basing contractor payment incentives or disincentives on achieved pavement smoothness. But the methods used to judge pavement smoothness as part of acceptance testing for new or reconstructed pavements are growing more refined. Also, the equipment used to obtain smooth pavements during construction is improving as digital and laser technology develops new products. For asphalt pavements, smoothness is just one piece of the quality-assurance puzzle (see Quality Management: How to Handle Materials, from the Source to the Site, in Better Roads' September is- sue, pp. 4-8). Other quality characteristics for acceptance measurement include asphalt mix properties such as asphalt content, gradation, volumetrics and as-built density. Portland cement concrete (PCC) pavement faces similar scrutiny. Smoothness brings benefits Pavement smoothness is more than just pleasing drivers with the sensation of driving on pavements that aren't rough; it's one of three pavement characteristics that reduce fuel consumption, as described by the 2010 publication by the Asphalt Pavement Alliance (APA), Smoothness Matters. The three pavement characteristics are tire/pavement rolling resistance, pavement stiffness and pavement smoothness. According to APA, tire/pavement rolling resistance is the loss of a vehicle's energy due to contact between the tires and the pavement. The loss of energy due to rolling resistance is small, about 15 to 20 percent, compared to other forces such 4 October 2013 Better Roads RoadScience_BR1013.indd 4 9/30/13 3:39 PM

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