Wisconsin Department of Transportation Highway Pavement Ride Analysis: The Effects of Specification Changes on Newly- Constructed Pavement
Abstract
Abstract
Smoothness specifications are implemented by all State Highway Agencies (SHA) to promote
overall roadway quality and optimize rider comfort. There are several key benefits of improved
roadway initial smoothness, the first of which is increased user comfort, fuel efficiency, and
increased roadway lifetime. Wisconsin Department of Transportation (WisDOT) ride specification
utilizes pay adjustments (incentives and disincentives) to achieve those objectives. This study
investigates the efficiency of these specifications and their changes over the last eleven years
(2007-2017), which includes five different specifications. The focus of this study is the effect of
specifications on newly constructed roadways over time and the incentive payments made for all
types of asphalt and concrete pavement. Though there are a broad range of studies which have
evaluated ride smoothness, there is a gap in studies which aggregate and capture specification
changes and their effects on roadway smoothness.
In this study, the investigation found that the specification changes have made an impact only on
specific asphalt and concrete types. Specifically, both mainline pavement types (HMA I and PCC
II) have exhibited smoother roads over the study period. As such, it is the resulting conclusion
that specifications should be more closely tailored to the different needs of each specific
pavement type. Notably, concrete and asphalt segments were found to be significantly different
from each other, yet the specifications group the different pavement types together when the data
does not support this grouping. The study also proposes different potential optimization cases
that WisDOT may pursue to improve current specification pay adjustments, which would have
cost savings to WisDOT.
Additionally, this study analyzes the effects of specifications on localized roughness, which are
segments of increased roughness, above a threshold. The current specification, with threshold of
200 inches/mile, has shown significant improvement over the past thresholds of 150 and 175
inches/mile, in terms of average roadway smoothness. The results from the concrete localized
roughness determined a potential for improved education so that segments are not mislabeled
and misanalysed. The specification changes did not impact concrete as significantly as it did for
asphalt. Though the thresholds are the same.
Lastly, the study analyzed project segments built under a warranty type specification. The
warranty analysis did show that warranty projects had a lower initial smoothness as compared to
non-warranty segments. The warranty program was suspended in 2012, due to long term quality
concerns.
Subject
WisDOT