The causes and consequences of edge breaks

Edge breaks are not just a local phenomenon. They are internationally highlighted as a major contributor to road accidents and fatalities. This is Part 1 of 2 in a series highlighting the problems and offering solutions and recommendations.

By Johan Muller*

Classified alongside potholes under the general ‘pothole pandemic’, edge breaks basically fall under the same mode of road surface deterioration. However, in addition to ageing and deformation in the wheel tracks, they are actually more dangerous and costly to repair properly. Edge breaks generally occur when the road shoulder is worn.

Professor Louis de Villiers Roodt, PrEng, published an excellent article, entitled ‘Road Safety, Maintenance and Claims for Damages, Lessons from cases and investigations’, which formed part of the proceedings of the 33rd Southern African Transport Conference (SATC 2014).

Roodt stated that claims against roads authorities have escalated since the capping of Road Accident Fund payouts. Among the major factors related to accidents, damage and fatalities are typical road failures, which are mainly related to surface failures such as potholes and edge drops/breaks. Related to these road surface failures, the failure of services and maintenance in the road reserve also contributes to crashes. Lessons learnt from case studies indicate that road failures do not necessarily have to be in the normal wheel tracks to be dangerous, and maintenance interventions of the full width of the trafficked lanes are essential.

A few of the causes of edge breaks and edge drops are detailed as follows: • Burst water pipes and sewerage systems in major and minor metropolitan municipalities often result in a sag curve, which is caused by aged water pipe and sewer reticulation systems. As an example, earlier this year the residents of Emfuleni Municipality had weeks of interrupted water supply due to burst pipes – and the same holds true for most formal and informal human settlements. Municipalities have not prioritised the replacement of these pipes for many decades. Water and even raw sewage dam and run over the road surfaces into the kerb inlets or wash away the support material next to the road surface. • Rainfall and stormwater run-off on to the roadside support structure and road reserve areas causes mass volumes of gravel and soil material to wash into drainage systems and water catchments in the absence of kerbs and stormwater reticulation. The

Road crossfall and washing away of gravel with additional support of some grass in places contributed to the edge breaks M6 Lynnwood Road edge breaks... shoulder gravel loss

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 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

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.