Is your car going bump in the the night? – pothole study

Road cavities in need of some dentistry: a pothole in Somerset West.

Potholes are bad news. Ask any driver who has had to fork out thousands of rands or any passenger who has been seriously injured because of potholes left unattended by road authorities.

They can cause damage and injuries and they can kill.

Potholes are probably the most visible road failure and clearly require maintenance standards to be implemented, says Dr Louis Roodt of the Department of Civil Engineering at Stellenbosch University.

In his recent doctorate in Civil Engineering, Dr Roodt proposes road maintenance standards for potholes, skid resistance, road sign visibility and readability, highway trees and roadside barriers.

These standards are important for road safety. Dr Roodt says most of the current standards focus solely on structural maintenance to carry traffic.

Rural roads targeted

According to him, most maintenance issues are common to rural and urban road networks. He, however, focuses on high-speed roads in rural areas where poor maintenance leads to severe injuries, fatalities and damage.

Dr Roodt explains that in terms of current road assessment guidelines a pothole is described as hazardous and having degree five severity if its surface dimension is greater than 300mm (the length of a ruler) and its depth greater than 50mm (about the length of your thumb).

In his view, a pothole of degree three severity with a diameter of 200mm and depth of more than 25 mm should be the trigger for repairs, as the cost would be lower and the further ingress of water speeds up deterioration.

Dr Roodt says the current road pavement management system monitors road conditions and reports the severity of potholes and the extent to which they occur.

Road engineers then prioritise the maintenance aimed at fixing the worst section, sometimes allowing potholes to grow beyond degree five severity.

While this is an operational decision for them, Dr Roodt says for safety’s sake, potholes should be fixed at degree three severity, irrespective of the extent, that is, even if it occurs isolated.

“The narrow wheels of bicycles, motorcycles and light vehicles dictate the size and depth of these failures from a safety point of view. When the pothole can ‘swallow’ the wheel, the risk of bending the rim, punching through or cutting the tyre is high and this could destabilise the vehicle,” he says.

More frequent inspections

“The inspection frequency for potholes is proposed as every two years for roads in good condition until weak sections are identified.

“Inspection frequencies must then be increased to once a month in the wet season and potholes must not be allowed to deteriorate beyond degree three,” he says.

“Provincial authorities have a legal duty based on societal values as expressed in public policy and legislation to implement road maintenance standards and to ensure reasonable safety for road users.”

Dr Roodt is adamant that roads must be maintained to a proper standard to achieve this.

Unfortunately, this does not happen very often due to lack of planning capacity, inadequate budgeting and poor supervision, particularly at middle management level, he says.

“Many maintenance standards that are proposed for safety are current sound practice, but implementation does not take place with the urgency that goes with the authorities’ legal duty to ensure safe roads.

“The complexity of maintaining roads is actually low and most actions are labour-based and can help create employment,” he adds.

Dr Roodt says because the backlog in maintenance contributes to hazardous road conditions and accidents, the standards proposed in his doctoral study will assist in quantifying the condition of road infrastructure and thus prioritise safety interventions.