Motorcycle Notes

No. 4 July 2000

Road Markings and Slippery Surfaces

This is the fourth in a series of VicRoads MOTORCYCLE NOTES. The purpose of MOTORCYCLE NOTES is to provide regular practical advice on motorcycle-specific aspects of design, maintenance and safety for VicRoads, Local Government, Government Agency and Consultant engineers and planners. MOTORCYCLE NOTES should be read in conjunction with: ‘Guide to Engineering Practice Part 15 – Motorcycle Safety’, (GTEP Part 15) Austroads. Sydney 1999.

The Need Significance of the Issue

Compared to other vehicles, motorcycles are vulnerable Motorcyclists are vulnerable road users, and the to slippery surfaces and unexpected changes in road severity of their crashes justifies close attention to friction. Practical examples preventive design and of areas where this can monitoring action in the occur include: road environment. Haworth (1999) reported ❑ Road markings, that the especially in the form of actively contributed to the raised white lines. occurrence of the crash in ❑ Slippery surfaces, such 15% of cases in the as steel plates. Victorian Motorcycle Case Control Study. ❑ Melted bitumen. A range of different site ❑ Loose surfaces. factors were covered, and ❑ Highly polished road the road surface friction surfaces at levels were the most intersections. important (see the diagram opposite). In such situations, any special attention paid to A third of all 1991-92 NSW motorcycle requirements motorcycle crashes did not will have broader beneficial involve any other vehicle impacts on other road (Austroads, 1999). Road users. surface friction factors can play a significant role in Oil and grease build-up on addressing such crashes. the middle of traffic is an example of a potential road surface hazard largely Current Guidance restricted to motorcycles. AUSTROADS GTEP Part 15 discusses a number of Single track vehicles tend to operate in the centre of specific areas where the road surface friction variations traffic lanes to avoid encroachment by larger vehicles. are not adequately covered by current general practice, This is precisely where such oil and other slippery and recommends “Ensuring adequate and consistent droppings build up and reduce available traction and surface roughness and skid resistance” as a design stopping power. principle. Specific areas identified as requiring attention beyond very different. The UK requires the highest levels of normal practice include: friction on tight bends, and on the approaches to , traffic signals, pedestrian and railway ❑ Some pavement markings offering inadequate skid crossings and minor junctions. resistance. ❑ Crack sealing without some Some Specific form of friction treatment can be extremely slippery. Responses ❑ Parallel grooving can reduce In heavily trafficked areas, a motorcycle stability. build-up of oil and grease ❑ The use of smooth steel deposits can occur in the centre plates over trenches can be of the traffic . This can be particularly hazardous. observed in many in major ❑ Sections of road with poor cities, and was first noted on UK due to their design. motorways. This deposit reduces surface friction, and can ❑ Uneven become very slippery when wet. treatments in the turning and braking areas at This part of the road is used only entrances to local by single track vehicles such as precincts. motorcycles - which are particularly vulnerable to oil or This is not a complete list, but grease deposits on the road summarises several of the surface. Such deposits are examples covered in Austroads particularly noticeable at traffic GTEP Part 15. lights on major city routes and should be treated when a build-up becomes evident. Surface Friction Levels Steel plates placed over temporary trenches on the The VicRoads standard specifications for routine road can become very slippery in the wet. So too can maintenance require treatment of patches where there tram tracks and steel joints. Judicious placement has been extensive seeping of bitumen through the and warnings of such potential hazards are desirable. surface or loss of aggregate. This arises when at least Decorative bluestone and cobblestone treatments also half of the aggregate has been lost, if there has been offer particular hazards to motorcyclists, especially over five square metres or more, or when when placed at the entrance to a precinct where there is extensive ‘crocodile’ cracking. The illustration vehicles are braking and turning. Advice from (GeoPave, 1998) shows an area on a curve appropriate motorcyclists at the design stage could be constructive for treatment. in minimising potential hazards. Some forms of crack repair can lead to slippery Motorcycles share with other vehicles a need for surfaces. Water ponding can also arise from some of the appropriate and consistent road surface friction levels. methods used to repair crocodile cracking. These They use different sections of the road and are more treatments can represent a hazard to motorcycles, vulnerable to sudden or unexpected changes in friction especially if located on a curve. on curves, intersections or braking areas. Special care Surface friction standards have slowly been developed is needed in road maintenance and design to ensure for use on UK roads (Rogers, 1991) and have some that their greater vulnerability to these factors is broad lessons for Australia, where conditions are often properly addressed.

Information resources: For further information, contact: AustRoads Pavement Research Group (1998). Treatment of cracks in flexible pavements. No 8. Manager, Traffic Management Services Rogers, M.P. & Gargett, T. (1991). A skidding VicRoads, resistance standard for the national road network. 60 Denmark St Highways and Transportation (April). pp. 10-16. KEW VIC 3101 GeoPave (1998). Surfacing chat. Edition 37, VicRoads Tel: (03) 9854 2256 Haworth, N. (1999). Road Factors in Motorcycle Fax: (03) 9854 2918 Crashes. VMAC Workshop: Motorcycling and the Email: [email protected] Road Environment. VicRoads, Kew June. TR2000068

VicRoads Publication Number 00479 http://www.vicroads.vic.gov.au