Since about 1997 the brightness of road markings on a number of New Zealand state highways has been increased. This study was undertaken to determine whether an increase in safety, as measured by reduced crashes, could be associated with the use of these brighter road markings. Specifications for the style of road markings used on New Zealand roads, including those with speed limits of greater than 70 km/h, are set out in the Manual of Traffic Signs and Markings (MOTSAM), and the Road and traffic standard 5: Guidelines for delineation on rural roads (RTS-5). On New Zealand’s rural roads, delineation is provided by a combination of edge marker posts carrying reflectors, painted road markings, and reflectorised raised pavement markers (RRPMs). MOTSAM and RTS-5 prescribe that the extent of delineation provided (intersections excluded) should increase as the annual average daily traffic (AADT) on the road increases, such that edge marker posts, then centre line road markings, then edge line road markings, and finally RRPMs are added progressively as traffic volume increases. As a result, the typical state highway rural road’s delineation is provided by a combination of edge marker posts, centre line road markings, edge line road markings, and RRPMs. The typical local authority rural road will have edge marker posts and centre line road markings only. Very low-volume rural roads (<100 vehicles per day) are usually without edge marker posts and are unmarked. Historically, the required brightness of the road markings has not been defined. About 1996, Transit New Zealand established a retroreflectivity (brightness level) requirement for road markings on state highways. From 1997, the introduction of performance-based contracts, entailing meeting of this retroreflectivity requirement, and the development of road marking materials and application techniques has tended to result in: • a significant increase in the retroreflectivity of the road markings being achieved, and • these levels of road marking retroreflectivity being sustained for long periods of time. Road safety and driver comfort are widely linked to visibility of the road ahead. Reflectorised road markings (in mid-life condition) offer a forward visibility 20 to 40 percent greater than that offered by non-reflectorised road markings (in mid-life condition). When travelling at 100 km/h, this increased forward visibility of the reflectorised road markings is 0.6 to 1.5 seconds more than that offered by non-reflectorised road markings. Lack of visibility of the road ahead is considered as a possible contributing factor in crashes relating to drivers losing control of their vehicle and/or running off the road. Improved road markings should improve the forward visibility for drivers and reduce the incidence of these types of crashes. The visual effect of reflectorised road markings compared with non-reflectorised road markings is more notable during dark conditions, rather than during light conditions, although there can be other effects, such as the reflectorised line being more durable, that will make the road marking also appear brighter in daylight. Therefore, while the improvement of delineation through use of reflectorised road markings should decrease delineation-related crashes in both light and dark conditions, the effect should be strongest during dark conditions. (Author/publisher)
Abstract