The 2009/10 summer rainfall season saw an unprecedented increase in the number of potholes and associated accidents on national, provincial and metropolitan 'sealed' roads. During the coming summer rains, motorists can expect even more potholes to develop on South Africa's roads, warns the Council for Scientific and Industrial Research (CSIR).

Concerted road maintenance and pothole repair would be needed urgently to curb that - to this end, the CSIR has compiled a guideline document that covers the causes, prevention and repair methods of potholes.

"People are up in arms about the huge number and size of potholes. To respond to this, we combined current expertise and practical examples and compiled a technical guide on the causes of potholes, means of curbing and preventing their formation, and providing specific instructions for proper fixing of the seven different categories of potholes identified. Given the extent of the situation countrywide, we believe the CSIR has an obligation, and is also ideally positioned, to produce such a guideline document," explains Hans Ittmann, Executive Director of CSIR Built Environment.

"The CSIR doesn't fix potholes - our mandate is to provide appropriate research and development solutions, as contained in the technical guide. The fixing of potholes is the responsibility of road owners," Ittmann comments. While the national road network belongs to the South African National Roads Agency Limited (SANRAL), municipal and provincial authorities are responsible for the roads under their jurisdiction.

The CSIR guidelines give comprehensive yet practical information on the effective, appropriate repair of the different categories of potholes. It is aimed at provincial, municipal and consulting engineers and road owners. It presents mechanisms for quality control of pothole repairs, and provides a standard form for use by inspectors during the field rating of potholes and identification of repair methods.

Along with a short, non-technical document, the guide is freely available for use by the various authorities and interested parties. "In this way, the CSIR wants to ensure all those responsible for road maintenance have access to the guidelines," notes Ittmann.

A study by the South African Road Federation indicates that potholes are costing motorists R50 billion in vehicle repairs and injury every year. "More potholes will lead to more claims against road authorities for damages to vehicles and even serious accidents due to large potholes," comments Dr Phil Paige-Green, author of the technical guidelines and infrastructure engineering expert at the CSIR.

"There is no doubt that water is the primary cause of potholes. The combination of unusually wet conditions over long periods, excessive traffic and poorly-maintained roads is a sure recipe for the development of potholes. To `safeguard¿ us against that, authorities have to ensure preventative maintenance of roads and timely, correct repair of existing potholes," Paige-Green advises.

"The condition of our national roads compares with the best in the world. SANRAL, owner of the national roads, has effective maintenance contracts in place. You may notice information boards along national roads where SANRAL provides a contact number for the public to report potholes and poor road conditions. After a pothole report on a national road is received from the public, the holes are fixed, properly, within a matter of days," says Paige-Green.

"Serious problems are experienced on most provincial roads. The provinces are allocated an amount for total roads activity, be it the construction of new roads or the maintenance and repair of existing roads. Budget constraints often lead to reactive and poor maintenance of roads. At municipal level, authorities have to use rates and taxes paid by the public to maintain roads - not everyone pays these, so financial constraints are once again a reality," Paige-Green notes.

The value of South Africa's road network is R1 047 trillion, with the current road maintenance expenditure standing at R9.2 billion. The road maintenance backlog amounts to R100 billion, with an annual road maintenance need of R32 billion.

'Healthy' road surfaces
When road surfaces are in a poor condition, water filters easily into the road structure - for example through cracks - thus weakening the structure and materials and causing potholes. The top sealant layer of black roads - commonly referred to incorrectly as 'tarred' roads, is bitumen. Tar was banned from use in national roads by SANRAL a few years ago to protect road workers against its apparent carcinogenic properties, and many provinces have since followed suit. Whereas tar is derived from coal, bitumen occurs naturally in small quantities in nature, while the vast majority of bitumen used worldwide is produced during the oil-refining process.

"Bitumen is a unique material - it becomes 'sticky' at the high temperatures used during construction, aiding the process of binding crushed stone and sealing a road. When it cools down to normal road-operating temperatures, it becomes 'non-sticky' and hardens to provide a good waterproof road surface. Over time, bitumen 'dries out', becoming harder and thus less flexible. You can compare it with the repeated bending of a piece of wire - it will eventually break. If aged bitumen surfaces are not maintained correctly, cracks will form under loading by heavy traffic, leading to pothole formation," Paige-Green expands.

Bitumen seals should thus be rejuvenated or restored before cracking occurs - to lay a new bitumen seal costs between R15 and R38 per m2, whereas the short-term restoration of dry bitumen layers using fog-sprays or rejuvenators can cost as little as about R5 per m2.

"It is thus imperative that funding be provided by the relevant authorities for preventative - rather than reactive - routine road maintenance leading up to summer rainfall seasons. That will go a long way towards saving costs of the repeated, patching of potholes which is often incorrectly done.

"The guides are available free - we encourage authorities to make use of it for providing appropriate training for road maintenance teams according to the methods stipulated in the technical guide," concludes Paige-Green.

Although the CSIR does not fix potholes, negotiations are underway with various training facilities to develop appropriate courses. The aim is to ensure that both the road inspectors and the pothole patching teams are trained to apply the principles outlined in the document effectively.

The technical and non-technical guides are available on the CSIR website: www.csir.co.za/pothole_guides