Impact of flexible pavement structural response on rolling resistance and vehicle fuel economy

Reduction in vehicle Fuel Consumption (FC) is one of the main benefits considered in technical and economic evaluations of road improvements. Surface roughness, texture, and structural response are the main pavement characteristics influencing rolling resistance. This paper investigates the increase in FC caused by the structural response of a flexible pavement (AC). It was proven that this energy is equal to the dissipated energy in the pavement itself due to the deformation of pavement materials under passing vehicles, including delayed deformation of viscoelastic materials and other damping effects that consume energy in the pavement and subgrade. The structural response to moving vehicles was calculated under different conditions of wheel loading, vehicle speed, and pavement temperature using a time domain dynamic viscoelastic solution (ViscoWave II-M). The energy dissipated (Wdiss) in the pavement is first evaluated and subsequently converted into FC excess, expressed as a percentage of total FC. The FC due to the structural response represents less than 0.56% of the truck’s FC at pavements average temperatures below 19°C. Fuel excess is about 1% at 27°C and can exceed 2% if the temperature is higher than 40°C at a speed of 57 km/h. It was also shown that the pavement structure affects significantly the results. Increasing the thickness of the layers reduces the Wdiss. A 50% increase in the AC thickness causes the Wdissto decrease by 43.5% from its original value. On the other hand, an increase of the aggregate base thickness has negligible effects on the Wdiss.