Author: William H. Parcells

Publisher:

Published: 2009

Total Pages: 44

ISBN-13:

Pavement smoothness is a major factor affecting the performance of the highway surface and the safety and satisfaction of the traveling public. Smooth pavement results in better gas mileage, less vehicle wear, and less driver stress and fatigue. Pavement smoothness is the single most important indicator of pavement condition as viewed by the traveling public. Many state highway agencies, including the Kansas Department of Transportation (KDOT), have adopted specifications that set forth a goal of minimal levels of roughness for newly built pavements. Some specifications also include significant incentive/disincentive provisions to encourage contractors to concentrate their efforts on building smooth pavements. This report highlights the development of the smoothness specification for Portland Cement Concrete Pavement (PCCP) beginning in 1985 and for Asphalt Concrete Pavement (ACP) beginning in 1990. The early specifications used the 0.2 inch Blanking Band while evaluating the traces generated using the manual California type profilograph. In 1986, incentive/disincentive clauses allowed bonus payment for PCCP constructed with less than 4 in/mile of surface roughness and penalty (reduced payment) for over 12 in/mile using the 0.2 inch Blanking Band. The implementation of the smoothness specification resulted in dramatic improvement in PCCP smoothness. In 1990 the stage was set for change. The initial projects requiring the use of the profilograph with the 0.2 inch Blanking Band to measure smoothness of ACP provided a high percentage (64%) of bonus level sections thus indicating the need for a modification to the existing specification. Similarly, the PCCP projects built in 1990 also had a high percentage (63%) of bonus level sections while using the 0.2 inch Blanking Band. However, there was one PCCP reconstruction project that had achieved about 47% bonus sections but produced a high frequency vibration in the vehicle when driving at normal speed. A review of the original profilograph traces revealed a short length sine wave roughness that was slightly less than 0.2 inches in amplitude and thus was almost completely covered by the 0.2 inch Blanking Band.