In 2015, nearly 73% of all fatal New Zealand road crashes occurred on rural roads. Nearly half (43.4%) of these rural road fatalities were the result of a vehicle losing control or running off the road, and were more prevalent on corners than on straight stretches. Delineation road markings and devices (such as edge marker posts and raised reflective pavement markers) are common tools used to enhance driving visibility and aid curve navigation, making them critical for reducing these crashes. However, the relative cost of establishing and maintaining this kind of delineation on low-volume rural roads poses a challenge. To optimise resources across the rural network, any delineation treatment should aim to achieve a balance between cost, safety and customer comfort. Consideration should also be given to the level of exposure within different road hierarchies in order to maximise resource value, where roads with higher volumes of customers receive higher levels of service (e.g. following the One Network Road Classification). The present investigation provides updated guidance on the optimum quantities, types and/or configurations of delineation required to achieve a minimum level of service across different rural road hierarchies. Rural roads for the purposes of this report include sealed roads in rural locations with a speed limit of 70km/h or over. There is also a strong focus on low-volume rural roads (i.e. those with average annual daily traffic of 3,000 or less), where cost-effective delineation solutions are more critical. The methodology consisted of five main phases: a literature review identifying evidence of international best practice and new technologies (phase 1); on-road trials testing different delineation solutions on rural New Zealand roads (phase 2); a driver survey examining how road users value delineation (phase 3); a discussion of the costs and benefits (phase 4); and a general discussion of the findings with recommendations, including recommended updates of the existing guidelines for rural road-marking and delineation (RTS 5; phase 5). For the on-road trials, four delineation treatments were tested. All four focused on assisting motorists in negotiating curves on rural roads, with the last three treatments focused on helping motorists in wet weather conditions. The four treatments included 1) the removal of edge marker posts (EMPs) on a straight stretch of road before a curve to trial targeted delineation, 2) the use of a structured marking edgeline on a curve, 3) the use of raised reflective pavement markers (RRPMs) on a curve, and 4) the use of audio tactile profile markings on the edgeline on a curve. Drivers’ hand positions and various vehicle characteristics (such as speed) were recorded for each trial and analysed for their effects according to treatment type. A key success metric for this study was to attempt to test delineation that provides visual conditions that are as close as possible to ideal or dry, daytime road conditions. The underlying assumption is that improvements in driver behaviour in poor visibility conditions could be benchmarked against dry, daytime behaviours. New evidence from the current investigation revealed that many of the delineation tools used had additional driving navigation benefits, such as EMPs providing cues to distance and speed (as well as long distance cues to road curves). There is also some evidence to support the use of delineation variation to intuitively guide drivers to be more attentive to higher risk locations, following the concept of self-explaining roads. Finally, in terms of wet weather treatments, new material applications (such as structured markings) resulted in better performance in rainy conditions. However, the combination of a traditionally applied, good quality road-marking with RRPMs is still more cost effective for rural settings, especially if the marking is on a high-grade chipseal (i.e. large stones), that already holds a high profile and good drainage (as opposed to a worn road surface). As a visual guidance tool, delineation devices have the ability to improve poor visibility environments (such as night or rain conditions) in such a way to enable drivers to preview the road ahead as if they were driving in as good as dry day conditions. Developing a best value delineation approach is all about understanding the effectiveness of different delineation solutions, so safety, cost, journey time and comfort can be optimised across the network. Based on the effectiveness of delineation on driver behaviour and safety, more effort should put into the standardised monitoring of specific types and qualities of delineation; and better monitoring and understanding of the contribution of the pavement surface to the effectiveness of the delineation treatment. Such initiatives should set a higher standard of performance on roads that have higher importance (i.e. for New Zealand following the One Network Road Classification system), or have higher exposure to poor visibility conditions (i.e. high annual rainfall). Actions of this kind would further our understanding of how to best optimise delineation performance, though would still require a shift from the culture of performance monitoring, from focusing on confirming observed underperformance to proactive mapping of asset performance using meaningful measures (such as sight distance). Initiatives of this kind are particularly relevant and sit at a critical stage of change, given there is an ageing population, as well as the rapid emergence of new technology that could utilise delineation if it were simply more consistent (i.e. autonomous vehicles). The following recommendations are made based on the findings from this research: • EMPs are cost-effective, all weather, delineation tools that have safety value and should be used on all road hierarchies (on straight stretches and curves). This study provides unique information that supports their use as critical guides in night-time driving conditions as they are evenly spaced at 100m gaps and hence, enhance judgement of speed and distance. Removing them from straight stretches of road would have unexpected and negative influences on speed. • Develop national guidance for consistent delineation treatments to support self-explaining road designs. This is where the driver is intuitively cued to an increase in actual risk through an increase in delineation, giving the driver explicit signals to adapt their behaviour (e.g. by increasing their attentiveness or reducing their speed). Such guidance could align with existing road categorisations, such as ‘curved’, ‘winding’ and ‘tortuous’ sections of road, based on the One Network Road Classification. This is also relevant for rapidly emerging technology (such as autonomous vehicles). • The RRPMs are a cost-effective, inclement weather solution that should be used increasingly on most rural roads, especially in areas with increased exposure to wet weather and wet weather crashes. They add complementary safety value even to high-quality markings (at least in the early phase of their life cycle). • RRPMs also prove that a highly retroreflective point source delineation treatment adds increased visibility to a traditional continuous line treatment when driving in the rain. Further work could examine point source treatments either without continuous road-markings, or with less frequently maintained road-markings. • Though the structured markings appeared to improve visibility for drivers in rainy conditions, there were issues with the particular marking trialled. As a result, the physical performance properties (retroreflectivity and luminance) were not high, presumably due to bead loss. Further testing is recommended. • Tangent point delineation solutions should be trialled at curves. Delineation is targeted to the inner curve where drivers look when they judge curve tightness. This means for a left-turning curve, the left edgeline and centreline at each curve could be re-marked more regularly than the less viewed right edgeline, which could reduce costs by about a sixth (if re-marked every second rotation). Alternatively, better materials or wider markings could be tested using this targeted approach. • There is some evidence of a gap between actual behavioural performance when driving in the rain and retroreflectometer readings in wet conditions. This should be examined more closely, as it appears the human eye detects some markings better than expected in rainy conditions. There is potential for identifying further improvements for new delineation treatments as well as possible cost savings. • The evidence here suggests techniques to provide a textured road surface (like the 2/4 aggregate used in trials) also appear to have additional visibility effects, providing not only better grip and drainage, but also better wet weather delineation performance. These added effects could be considered in road surface decision making. • Consideration should be given to providing better communication plans and increasing transparency with the public around any removal or reduction in levels of service for high-visibility infrastructure (such as delineation). The findings suggest public backlash can be mitigated if the public understands why there has been a shift in spending. A proactive communications plan allows the development of a public profile of the safety interventions being focused on, and why this is important to optimise area-wide safety at the local level. (Author/publisher)
Samenvatting