The perks of overloading

The tirade against vehicle overloading is erroneous. There is a misunderstanding among laypersons that roads are designed for 8.2 ton axle loads. This figure has no relevance for the design of the road except as a unit of measurement. It was selected arbitrarily by the American State Highway Officials (AASHTO) in their road tests in the 1950s for developing pavement design methods, and is being universally used for pavement design. Any other unit of measurement could have been adopted. It is important to note that if the impact of load on the road increases by 4th power, the strength of the road increases with thickness of pavement in log ratio. The marginal cost of strengthening the road to bear higher axle loads is abysmally small and can be ignored. Highway engineers are now considering virtual design of road pavements for all loads and all time to come.

If loads are restricted, the cost of transport will increase by 30 to 50 percent and more vehicles will be required to carry the same load. This will increase the volume of traffic and require widening of roads earlier than required -- which will be more expensive. As such, vehicle overloading is a blessing in disguise. It saves the cost of transport to users and cost of widening roads to the highway agency.

Abdul Majeed

Islamabad