The majority of Canadian geography is in a wet-freeze environment. In winter, pavements
and the underlying subgrade freezes. During the spring thaw, water in the pavement structure
and subgrade reduces the stiffness (resilient modulus) of some of the pavement layers and in
particular the subgrade. This reduces the overall structural capacity of the pavement. In order
to “protect” the pavement from excessive damage, most agencies institute a spring load
restriction. During this period, the axle loads are restricted to half or three quarter the loads
permitted during other periods of the year. While this practice is intended to mitigate
pavement damage the application and removal of load restrictions is not typically based on a
technical analysis of pavement capacity but rather on “historical dates” and it is very
disruptive to the trucking industry.
Over the past 10 years, Canadian highway and municipal agencies have been working on the
implementation of mechanistic-empirical (M-E) designs for their roadway infrastructure.
Many agencies are working on aspects of M-E design, focusing on particular aspects that have
the most impact on their pavement design procedures working towards calibration of the M-E
models and adoption M-E design procedures. Until recently, most Canadian roadway
agencies have utilized the pavement design procedures established by the American
Association of State Highway and Transportation Officials (AASHTO). The AASHTO design
procedure is limited to only a few key parameters such as resilient modulus, equivalent single
axle loads (ESALs), etc. The M-E design procedure is a much more robust in that it is capable
of a more rigorous pavement design.
This paper uses an M-E analysis to determine the impact of load restrictions on pavement
damage for typical municipal roadway pavement sections from Ontario. The cost of future
pavement repairs as a result of the damage is compared to the cost of the trucking industry in
terms of additional trips, reduced loads, etc. Recommendations are made for an M-E analysis
methodology to assist roadway agencies to mitigate pavement damage while permitting
efficiencies for the trucking industry.