Surface-tyre friction: Case studies and theoretical models
T J Waters and P J Vardanega
Refereed Paper
This paper has been critically reviewed by at least two recognised experts in the relevant field.
Received: October 2011.
Abstract
This paper gives a brief review of the history of some skid resistance studies from the 1930s to the present day. Emphasis is placed on data relating to forward skidding tests, which measure the coefficient of friction directly, and the effective coefficient of friction obtained by stopping-distance tests. This paper aims to quantify the effects of vehicle speed, texture depth and tyre tread depth on the coefficient of friction and stopping distance of vehicles. Using data collected by the Institute for Road Safety Research SWOV (Netherlands), a modified texture depth expression that incorporates both tyre tread depth and road surface texture is introduced. This modified texture depth is shown to correlate with the decrease in the coefficient of friction with speed. The link between texture depth and stopping distance is also explored.
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Analysing freeway traffic-incident duration using an Australian data set
A T Hojati, L Ferreira, P Charles and M R Kabit
Refereed Paper
This paper has been critically reviewed by at least two recognised experts in the relevant field.
Received: December 2011.
Abstract
This paper investigates incident duration and identifies contributing variables for Australian conditions. The paper presents a new framework for comprehensive traffic-incident data mining and analysis towards an incident delay model and travel-time reliability modelling. Twelve months of data were collected, analysed and the results are presented in this paper. The findings suggest that debris, breakdown and multiple-vehicle crashes are the major sources of incidents on freeways. Furthermore, freeway incident duration varied across the types of incident and time of the day and whether it was a week day or weekend day. However, there were no significant differences inrelation to day, week or month of the year. Significant variables on incident duration were identified using an ANOVA test for each type of incident. In addition, the findings of this study reveal a high variance of incident duration within each incident type. A variety of probability distribution functions were employed to test the best model for the duration frequency distribution for each category of incident. Log-normal distribution was found to be more appropriate for crashes, but log-logistic distribution was more appropriate for hazards and stationary vehicle incidents.
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An historical review of the assessment and management of congestion
Maxwell G Lay
Review Paper
This paper is based on a reviewed presentation to the Conference Blocked Arteries: Circulation and Congestion in History, Institute of Historical Research, University of London, November 2010. It has not subsequently been published elsewhere. It has been accepted for publication here without further review to provide an accessible published discussion of an interesting topic.
Abstract
The paper notes that most trips will involve various intrinsic delays and impedances. One of the problems in studying congestion, both historically and operationally, is to differentiate between such intrinsic delays and congestion. A companion paper explored this question operationally and this paper examines congestion in an historical context. The paper gives many examples of how claimed congestion has been used as a metaphor for various other ills perceived by the claimants. Indeed, it is shown that the term ‘congestion’ only began to be applied, and then somewhat emotively, to traffic late in the 19th century. The cost of congestion became a common topic and it is suggested that the 20th century estimates were usually shakily-based overestimates. It is argued that one source of road-based traffic congestion has been the historical lack of a pricing mechanism for road use. However, the historical review indicates that a greater factor was that the advent of the petrol-powered motor vehicle at the beginning of the 20th century, with its quantum jump in travel capabilities, caught all those involved by surprise – from suppliers to operators to managers to regulators to planners to policymakers. Today, the paper suggests that there is still much lost ground to be regained. More specifically, the paper concludes that ‘traffic congestion’ has often been an emotive term, defined and used in many inappropriate ways that have often led to incorrect conclusions or inferences. It is therefore not surprising that there is a poor track record of successful planning for congestion and that there is little evidence of this record improving.
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Riding a mile in their shoes: Understanding Australian metropolitan rail passenger
Kirrilly Thompson, Lily Hirsch, Simone Mueller Loose, Vinathe Sharma-Brymer, Sophia Rainbird, Kirsteen Titchener, Matthew Thomas and Drew Dawson
Invited Paper
An earlier version of this paper was peer reviewed and presented at the 9th World Congress for Rail Research in Lille, France on the 23rd of May, 2011. It is published here without further peer review at the invitation of the Editor in order to place it on the accessible record and to make it available to a wider audience.
Abstract
Metrics such as passengers per square metre have been developed to define optimum or crowded rail passenger density. Whilst such metrics are important to operational procedures, service evaluation and reporting, they fail to fully capture and convey the ways in which passengers experience crowded situations. This paper reports findings from a two year study of rail passenger crowding in five Australian capital cities which involved a novel mixed-methodology including ethnography, focus groups and an online stated preference choice experiment. The resulting data address the following four fundamental research questions: 1) to what extent are Australian rail passengers concerned by crowding, 2) what conditions exacerbate feelings of crowdedness, 3) what conditions mitigate feelings of crowdedness, and 4) how can we usefully understand passengers’ experiences of crowdedness? It concludes with some observations on the significance and implications of these findings for customer service provision. The findings outlined in this paper demonstrate that the experience of crowdedness (including its tolerance) cannot be understood in isolation from other customer services issues such as interior design, quality of environment, safety and public health concerns. It is hypothesised that tolerance of crowding will increase alongside improvements to overall customer service. This was the first comprehensive study of crowding in the Australian rail industry.
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