Abstract:
The road network in South Africa, particularly in urban areas, is experiencing a steady increase in traffic
volumes and congestion. Speed has a significant effect on the response of flexible pavement systems
to traffic loading. Truck tyre loads are more often analysed as a static load in order to simplify the
computations, although in reality the pavement system is subjected to a dynamic load. This paper
investigates the influence of truck speed on flexible pavement system response to moving traffic
loading. A truck with standard axle loads was used to conduct runs at controlled speeds and wander
over a full-scale instrumented pavement test sections on road R104 east of Pretoria. The findings of
this research indicate that pavement deflections increase exponentially as the truck speeds reduce to
speeds below 30 km/h. Furthermore, deflections decrease marginally as the truck speeds increase to
speeds greater than 40 km/h. Different flexible pavement systems present different exponential factors
that reflect differences in sensitivity of the pavement systems to changes in truck speed. It is thus
essential to introduce adjustment factors to deflection measurements done at different truck speeds
on different pavement systems in order to compare such deflection data.
