Nicole van Nes

Improving homogeneity by dynamic speed limit systems

Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12 road sections in a driving simulator. The speed limit system (static-dynamic), the sophistication of the dynamic speed limit system (basic roadside, advanced roadside, and advanced in-car) and the situational condition (dangerous-non-dangerous) were varied. The homogeneity of driving speed, the rated credibility of the posted speed limit and the acceptance of the different dynamic speed limit systems were assessed. The results show that the homogeneity of individual speeds, defined as the variation in driving speed for an individual subject along a particular road section, was higher with the dynamic speed limit system than with the static speed limit system. The more sophisticated dynamic speed limit system tested within this study led to higher homogeneity than the less sophisticated systems. The acceptance of the dynamic speed limit systems used in this study was positive, they were perceived as quite useful and rather satisfactory.

Attitudes towards current and lowered speed limits in Australia

The present study was concerned with gaining a greater understanding of the Australian communitys attitudes towards both the current and proposed lower speed limits. An online survey was administered in four states (Victoria, South Australia, Western Australia, and Tasmania), with a total of 4100 respondents recruited. The survey focussed on attitudes towards speed limits for four different road types, and the sample was stratified according to age, gender, and area of residence. It was found that most respondents were able to correctly identify the speed limit for local residential streets and major urban arterials, although their knowledge of rural speed limits was considerably lower. The majority of respondents were in favour of the proposed lower speed limits on 100 km/h two-lane undivided rural roads and on rural gravel roads, but only about one-third supported lower limits in urban areas. A cluster analysis revealed that there were varying characteristics between respondents who were more or less likely to support speed limit reductions, across a number of demographic, socio-economic status, and driving behavior variables. These results provided important guidance regarding groups that could potentially be targeted in speed-related interventions, as well as highlighting the potential for lowering speed limits in Australia, particularly on rural roads.

An exploration of alternative intersection designs in the context of Safe System

Fatal and serious injury crashes persist at intersections despite current efforts to address this. Little research specifically investigates the role played by existing intersection design in perpetuating serious intersection crash outcomes despite an increasing move to incorporate Safe System design on to roads. This paper identifies design principles deemed important to align intersection design with Safe System approaches, including exploring the impact of speed and angle on overall kinetic energy of a crash. Existing as well as new intersection designs are presented that are believed to incorporate the identified principles. An assessment is made of the alignment of the new and existing designs with the identified principles.

The value of site-based observations complementary to naturalistic driving observations: A pilot study on the right turn manoeuvre

Naturalistic driving studies are increasingly applied in different shapes and sizes. The European project PROLOGUE has investigated the value and feasibility of a large-scale naturalistic driving study in Europe. Within PROLOGUE several pilot studies have been conducted in different countries. The Dutch field trial investigated the value and feasibility of adding site-based observations to in-vehicle observations. In this trial, one intersection was equipped with cameras for site-based observation. Additionally eight cars were equipped of drivers crossing this intersection regularly. On this small scale, combining the two observation methods turned out to be technically feasible. It was possible to recognise the instrumented vehicles in the site-based video data, to match cases from the different observations and the speed measures from the separate studies appeared to be similar. The value of combining these two observation methods lies in the possibility to enrich the data from one study with complementary data from the other study. The study illustrated that each type of observation has its unique values. From in-vehicle data it is possible to look in detail at the driving behaviour of the participants over time and in different situations. The site-based study offers information about the position and speed of other road users surrounding the participants vehicle, including vulnerable road users such as cyclists and pedestrians. Two values of adding site-based observations to in-vehicle observations were identified: to obtain more in depth understanding and to relate the behaviour of participants of the naturalistic driving study to behaviour of the full population of drivers (non-participants). For a future (large-scale) naturalistic driving study two research topics are identified that could benefit from these complementary observations: driving behaviour in relation to specific infrastructure and the interaction between drivers and vulnerable road users.

The influence of environmental factors on speed choice

Speed and homogeneity of speed are important factors for safe and sustainable traffic. Lower speeds and more homogeneous speeds are safer and cause less pollution. Speed behavior is influenced by environmental factors as well as by personal factors. Understanding the relation between speed behaviour and the influencing factors offers clues for appropriate countermeasures against inappropriate and excessive speed. This study investigates the relation between speed and environmental factors for single lane rural roads, one of the most hazardous road types in the Netherlands. The study uses data from two provincial road authorities. Data consists of speed data from loop detectors, road design characteristics, characteristics of the road environment, and police enforcement. The first objective of this study is to validate the outcomes of earlier studies reported in literature, such as photograph studies and self reported speed behaviour studies. In this study, the influence of the same external factors on percentile speed measures and homogeneity measures from speed loops are investigated. A second objective is to refine the credibility models by adding external factors, if relevant. The results of this study replicate some of the results that were found earlier, but not all. No additional factors were found; results and consequences will be discussed.