Abstract:
In many countries road traffic is growing rapidly in volume, size and weight of the
vehicles. As a consequence, highway engineers are concerned with designing new roads
or the strengthening of existing road surfaces which require reliable information about the
distribution of axle loads for existing traffic as well as information of national or regional
axle load trends. This information is required for accurate forecasts of the axle loads that
a road will have to carry over its design life.
The importance of reliable traffic information for pavement design purposes is obvious
by the widely accepted engineering law that the degree of pavement damage caused by an
axle load is proportional to approximately the fourth power of the axle load. This implies
that the heaviest ten percent of axle loads can often cause more pavement damage than
the rest of the traffic combined. To provide adequate information on axle load
distributions, roadside surveys of axle loads are required. Such surveys can conveniently
be made using portable wheel or axle weighing devices that are widely available.
This project describes the methodology and procedures required to carry out both traffic
counts and axle load surveys. This also includes methods of traffic volume and axle load
data analysis for pavement design and rehabilitation purposes. A traffic loading
evaluation should be performed as part of the overall evaluation of a pavement to assist in
determining rehabilitation needs. An evaluation of traffic loading is also important for
initial design.
