Managing Motorways and Urban Arterials in Australia: Country Report for Australia

AbstractAustralian States have been investing heavily in managed motorway. It was acknowledged some time ago that the motorways that had slow moving congested traffic caused a considerable loss of value to the community. The concept of Productivity was applied to Motorways and since become a key performance indicator used to rate different motorway systems. The approach to motorway management has been based on established practices overseas although different algorithms are being developed in Australia and subsequently evaluated. This paper describes the processes used by Australian States to manage motorways and it describes the current research into new techniques.The management of motorways cannot be undertaken without consideration of the urban arterial network. It is therefore important to see the network as a whole noting that drivers tend to change their routes so that both the motorways and the arterial work in unison to provide the level of service to the user. It is therefore important that the performance of the arterial road system be maximised. The paper outlines some of the research that is directed at maximising the arterial road, using detectors on the departure side of signalized intersections to evaluating the potential for significant improvement in signal re-timing.Finally the paper will outline the use of the Highway Capacity Manual in Australian traffic engineering practices. It should be understood that Australia has used SIDRA for intersection analysis for some time and although many of the concepts of the HCM are used in SIDRA, it contains many elements and calibration factors that are peculiar to Australia

Comparison of homogeneous and heterogeneous motorised traffic at signalised and two-way stop control single lane intersection

Results of a microscopic model of mixed motorised traffic consisting of short vehicles, (e.g. cars), and long vehicles, (taken to be double the length of the short vehicles), for an urban two-way single lane intersection are presented here. We model the intersection using both signalised and un-signalised stop control rules. The model allows for the detection of bottleneck activity in both homogenous and heterogeneous traffic conditions, and was validated by means of field data collected in Dublin, Ireland. The validated model was used to study the impact of inclusion of long vehicles on traffic performance in an urban environment. Traffic mix is, however, taken to be dominated by short vehicles overall, in argument with observed live data collected

Application of network traffic flow model to road maintenance

The study shows how the evolution of two-way traffic flows on a local highway network can be predicted over time using a network-level traffic flow model (NTFM) to model both urban and motorway road networks. After a brief review of the main principles of the NTFM and its associated sub-models, the paper describes how a maintenance worksite can be modelled using a roadwork-node sub-model and a network solution routine in the NTFM. In order to model the two-way traffic flow in the road network, an iterative simulation method is used to generate the evolution of dependent traffic flows and queues. The NTFM has been applied to model the traffic characteristics and the effects of maintenance activities on the local Loughborough–Nottingham highway network. The study has demonstrated that the methodology is useful in selecting various worksite arrangements in order to reduce the effects of maintenance on road users

Dialect contact and distinctiveness: The social meaning of language variation in an island community

In this paper, we analyse linguistic variables which are well-established in British English, the vowels in the trap and bath lexical sets. We demonstrate that the social meanings of these variables are both historically substantiated and locally-elaborated. Our data is taken from the speech of individuals living on the Isles of Scilly, a group of islands off the south-west coast of England. Our initial analysis shows that trap and bath variants found on the islands are linked to contact with Standard English English, on the one hand, and the nearest neighbouring variety of Cornish English, on the other. The general distribution of variants is shown to reflect educational differences amongst our speakers. However, two case studies show speakers using forms atypical of their education type in order to position themselves in interactionally-dynamic ways. This reveals how speakers exploit the multidimensional meanings of linguistic variants to reflect and construct local practices and alignments

Prefrontal cortex activation and young driver behaviour: a fNIRS study

Road traffic accidents consistently show a significant over-representation for young, novice and particularly male drivers. This research examines the prefrontal cortex activation of young drivers and the changes in activation associated with manipulations of mental workload and inhibitory control. It also considers the explanation that a lack of prefrontal cortex maturation is a contributing factor to the higher accident risk in this young driver population. The prefrontal cortex is associated with a number of factors including mental workload and inhibitory control, both of which are also related to road traffic accidents. This experiment used functional near infrared spectroscopy to measure prefrontal cortex activity during five simulated driving tasks: one following task and four overtaking tasks at varying traffic densities which aimed to dissociate workload and inhibitory control. Age, experience and gender were controlled for throughout the experiment. The results showed that younger drivers had reduced prefrontal cortex activity compared to older drivers. When both mental workload and inhibitory control increased prefrontal cortex activity also increased, however when inhibitory control alone increased there were no changes in activity. Along with an increase in activity during overtaking manoeuvres, these results suggest that prefrontal cortex activation is more indicative of workload in the current task. There were no differences in the number of overtakes completed by younger and older drivers but males overtook significantly more than females. We conclude that prefrontal cortex activity is associated with the mental workload required for overtaking. We additionally suggest that the reduced activation in younger drivers may be related to a lack of prefrontal maturation which could contribute to the increased crash risk seen in this population

Self-Control of Traffic Lights and Vehicle Flows in Urban Road Networks

Based on fluid-dynamic and many-particle (car-following) simulations of traffic flows in (urban) networks, we study the problem of coordinating incompatible traffic flows at intersections. Inspired by the observation of self-organized oscillations of pedestrian flows at bottlenecks [D. Helbing and P. Moln\'ar, Phys. Eev. E 51 (1995) 4282--4286], we propose a self-organization approach to traffic light control. The problem can be treated as multi-agent problem with interactions between vehicles and traffic lights. Specifically, our approach assumes a priority-based control of traffic lights by the vehicle flows themselves, taking into account short-sighted anticipation of vehicle flows and platoons. The considered local interactions lead to emergent coordination patterns such as ``green waves'' and achieve an efficient, decentralized traffic light control. While the proposed self-control adapts flexibly to local flow conditions and often leads to non-cyclical switching patterns with changing service sequences of different traffic flows, an almost periodic service may evolve under certain conditions and suggests the existence of a spontaneous synchronization of traffic lights despite the varying delays due to variable vehicle queues and travel times. The self-organized traffic light control is based on an optimization and a stabilization rule, each of which performs poorly at high utilizations of the road network, while their proper combination reaches a superior performance. The result is a considerable reduction not only in the average travel times, but also of their variation. Similar control approaches could be applied to the coordination of logistic and production processes

A safe system based approach to selection of clear zones, safety barriers and other roadside treatments

On average, 560 fatal run-off-road crashes occur annually in Australia and 135 in New Zealand. In addition, there are more than 14,000 run-off-road crashes causing injuries each year across both countries. In rural areas, run-off-road casualty crashes constitute 50-60% of all casualty crashes. Their severity is particularly high with more than half of those involved sustaining fatal or serious injuries. This paper reviews the existing approach to roadside hazard risk assessment, selection of clear zones and hazard treatments. It proposes a modified approach to roadside safety evaluation and management. It is a methodology based on statistical modelling of run-off-road casualty crashes, and application of locally developed crash modification factors and severity indices. Clear zones, safety barriers and other roadside design/treatment options are evaluated with a view to minimise fatal and serious injuries – the key Safe System objective. The paper concludes with a practical demonstration of the proposed approach. The paper is based on findings from a four-year Austroads research project into improving roadside safety in the Safe System context

The probability of delay to minor stream drivers at a limited priority freeway merge

Gap acceptance theory is traditionally based on the interactions when a minor stream of drivers wish to enter a major stream generally assumed to have absolute priority. However, some researchers have felt that this model is not always appropriate. In analysing freeway merging behaviour, it was found that major stream drivers have only limited priority, suffering some delay. This report discusses the development of a relationship to predict the probability of merging drivers being delayed at a limited priority freeway merge after leaving an unsignalised intersection upstream. This quantity is a valuable performance measure itself, and with average merging delays able to be predicted, facilitates tangible merge area performance assessment. Equations formulated to represent probability of delay against degree of saturation are compared. A new relationship is proposed, which indicates that critical gap has only a marginal influence on probability of merging delay, and that flow rates in both minor and major stream have a significant and adverse influence. It is suggested that the maximum acceptable (or practical) probability of merging delay should be approximately 60%. This gives results which are similar to maximum measured downstream kerb lane flows