ROADS & BRIDGES
results in standing water in and around the road edges. The standing water and lateral ingress of excessive moisture then soften unstabilised verges, which results in base material damage, a reduction in stiffness and the more rapid deterioration of subsurface and surrounding support material essential for road surface stability and durability in typical road designs.
What South African road accident statistics tell us R101 between Bon Accord and Pyramid Stations, north of Tshwane
Excellent gravel shoulder maintenance and paved shoulder. No evidence of edge breaks
cost of the replacement of such material is astronomical and has a negative impact on our limited natural resources. • Informal use of unsurfaced roadsides and road reserves by selfish and impatient public road users and public transport operators (especially on major trafficked routes) results in and contributes to major mechanical breaks on road edges. Furthermore – and apart from this bad driver behaviour being a nuisance and frustration for law-abiding citizens – it subsequently causes soil erosion due to water erosion, wind erosion and the friction of tyres of various vehicle types. Roadside materials are often carried on to adjacent road surfaces and, apart from the silt and gravel that may cause a loss of traction and windscreen damage, also result in dust and a reduction in visibility (another major cause of accidents). • A lack of grass cutting, drainage system cleaning/clearing, and other regular roadside maintenance interventions often
When I requested the assistance of the South African Road Federation (SARF), the lack of availability of national statistical data was evident. This is despite the high level of focus on road safety that SARF facilitates as a major custodian and excellent training facility – a crucial element of the SARF mandate. Basil Jonsson, operations director at SARF, referred me to Craig Proctor-Parker, founder of Accident Specialist, a company based in Kloof, KwaZulu-Natal. After a relatively quick discussion with Proctor-Parker, he opened a wonderful opportunity to discuss the topic. Although we cannot provide an accurate statistical mathematical figure in this article, it is evident that a large proportion of accidents investigations indicate (as Roodt has also stated) that edge breaks and drops are either causing accidents or exacerbate the outcome of an accident. The investigations carried out by Accident Specialist cover a large array of clients (including state and other authorities).
Tools to address edge breaks and drops In the USA, many states have guideline documents to address the main causes of and provide remedies for the high-risk deterioration experienced on their road networks. A paper entitled ‘An investigation of urban area run off road crashes in Western Australia 2005-2009 (RR 10-005)’ produced some revealing data. It was published by the Curtin-Monash Accident Research Centre and indicated that single vehicle run-offroad crashes accounted for around one in ten crashes, and significantly contributed to serious injuries. With appropriate statistical data for urban areas, their investigation describes the epidemiology of single vehicle run-off-road crashes. They considered a range of safe road and roadside countermeasures and others to reduce the incidence of crashes and injury severity. Roadside barriers and audio-tactile edge-lining, for example, are commonly known to be important and effective countermeasures for run-off-road crashes.
ACKNOWLEDGMENT Bituminist Consulting aims to disseminate valuable information and promotes collaborative engagements in the interests of the road industry, the binder supply and manufacturing fraternity. Continuous improvement and adaptation to the challenges experienced locally and internationally leads to new developments. In preparation for this article, various passionate practitioners provided input and dedicated their time free of charge. Special thanks to the passionate people like Basil Jonsson at SARF; Craig Proctor-Parker and Eloise Deschamps at Accident Specialist; Johannes Lambert at Tosas; Nastassja Nielsen, Dave Collins and Wynand van Niekerk at BSM Laboratories; Louis Walstrand and Mark Knowles at Specialised Road Technologies; and Pieter Molenaar at Royal HaskoningDHV. A special thanks also to Professor Roodt and our freelance field photographer, Pierre Roux.
The two major crash types that were occurring in the Perth metropolitan area in 2005-2009 were identified as: - vehicles running off the road and crashing into an object or involved in a non-collision (rolling over) - vehicles running off the road and colliding with a pedestrian or carriageway. The role of speed, road alignment, and type of collision as contributors to injury severity were considered. Within the South African context, Accident Specialist’s investigations to date point to collapsed and crumbling or drop-off edges as contributing factors for local road crashes to date. *Johan Muller is the founder of Bituminist Consulting. He holds an MSc in Organic Chemistry and has worked in the roads industry for more than 27 years.
IMIESA September 2021
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