Road and Transport Research Abstracts Vol. 20 No. 3

The effect of binder film thickness on asphalt cracking and ravelling

John WH Oliver

Peer reviewed paper: This paper has been critically reviewed by at least two recognised experts in the relevant field.


Abstract
Asphalt mixes require a minimum amount of bitumen binder to ensure cohesion, durability and a minimum level of fatigue resistance in a mix after it is placed. In the Austroads asphalt mix design procedure this is addressed by the requirement for
a minimum binder film thickness value of 7.5 μm. This requirement was based on the results of field and laboratory investigations. The most useful evidence was the field performance of VicRoads’ mixes placed with a range of film thicknesses between 1962 and 1975. Information on the film thickness used by VicRoads at a later period is also presented, together with the results of a laboratory investigation to determine the effect of binder film thickness on asphalt fatigue life. The separate effects of a change in binder content and a change in compaction on fatigue life were determined from these laboratory results. A further study showed that where increase in film thickness was caused by increase in binder content, the expected increase in fatigue life occurred. However, where the same calculated increase in film thickness was caused by a decrease in filler content there was no change in fatigue life. It was concluded that, based on the available data, the existing minimum film thickness requirement of 7.5 μm should be retained

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A simple prediction model for asphalt surface texture incorporating mix gradation and air voids

Paul J Vardanega

Peer reviewed paper:  This paper has been critically reviewed by at least two recognised experts in the relevant field.

Abstract
This paper presents the results of a preliminary study that seeks to show how asphalt grading and air voids are related to the texture depth of asphalt. The fiftieth percentile particle size (D50) is shown to be a good predictor of texture depth measurements from a collected database of field and laboratory studies. The D50 is used to normalise collected texture data and this ‘relative texture’ is shown to correlate with air voids. Regression analyses confirm that air voids should be included along with a measure of gradation in the interpretation of asphalt surface texture. The derived formulae are used to develop correlation charts.

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Small-scale accelerated pavement testing machine

John Patrick, Padmanathan Kathirgamanathan, Shaun Cook, Philip Herrington and Haran Arampamoorthy

Peer reviewed paper : This paper has been critically reviewed by at least two recognised experts in the relevant field.

Abstract
A simple apparatus for the testing of granular pavement materials at near full-scale and with realistic tyre loadings was developed and validated. The system allows for construction and testing of pavement materials and designs in a manner similar to that achieved with full-scale accelerated loading facilities, but at a much reduced cost. An inexpensive, non-contact, laser-based method for the measurement of pavement profile has also been developed for use with the apparatus. Software analysis of digital photographs allows detailed profiles to be determined and rut depth to be calculated with minimal delay to pavement trafficking.

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Distribution of the noise level maxima from the pass-by of vehicles in urban road traffic streams

A.L.(Lex) Brown and Deanna Tomerini

Peer reviewed paper: This paper has been critically reviewed by at least two recognised experts in the relevant field.


Abstract
The paper reports the distributions of noise level maxima, LAFmax, generated during the pass-by of over 85 000 vehicles in service on urban arterials and motorways. These were measured under normal traffic and vehicle operating conditions on multilane roadways. They are indicative of the instantaneous maximum noise levels that would be experienced in the free field at the set-back distance of the facades of the first row of many dwellings fronting urban roadways in Australia, from vehicles travelling in the nearside lane. Noise levels are reported separately for four classes of vehicle and for roadways with five different posted speed limits. Results have been standardised as free-field levels 15 m from the centreline of vehicle travel. The data were collected in Brisbane but can be assumed to be representative of noise level maxima from vehicles operating throughout Australia. Maximum noise levels increase with vehicle class (from cars through to articulated trucks) and with roadway speed limits. The within-vehicle-class variance is large and the distributions of maxima from different vehicle classes overlap extensively. Sound Power Levels of the observed vehicles agree well with those from the European IMAGINE emission model. This investigation contributes essential information regarding the source and levels of noise events adjacent to urban road networks – the likely determinant of human sleep disturbance.

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Development of an accessibility metric and its application to Melbourne

Ian Espada and James Luk

Invited paper: This paper is adapted from a paper originally reviewed and presented at the 2011 Conference of the Australian Institute of Traffic Planning and Management, held in Melbourne in August 2011. It is published here at the Editor’s invitation, without further review, to make it accessible to a wider audience.

Abstract
This paper describes the development of an accessibility metric for performance monitoring and policy analysis. The developed accessibility metric incorporated transport cost and opportunities at the end of a trip to calculate an accessibility score. It covers employment, school and shopping and recreation trip purposes. It includes accessibility by four modes including car, public transport, cycling and walking. Melbourne was analysed as a case study using the metric. The accessibility profile of Melbourne was illustrated. The relationship of accessibility to the propensity to travel long distances, non-car mode share, and property price were investigated. The analysis showed that (i) zones with higher accessibility coincided with zones wherein people travel less distances; (ii) higher public transport, walking and cycling accessibility coincided with higher non-car mode shares for work trips but not for other trip purposes; and (iii) areas with higher public transport, walking and cycling accessibility levels coincided with areas with higher property prices.

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Transportation modelling for model walking and cycling communities

Angus Bargh and John Kelly

Invited paper : A version of this paper was originally presented at the 2011 Transportation Group Conference of the Institution of Professional Engineers, New Zealand, where it won the NZAA Award for Best Paper. It is published here by permission at the Editor’s invitation, with minor edits but without further review, to acknowledge the paper and to bringits subject to the attention of a wider audience.

Abstract
This paper discusses an innovative approach to the development and application of a multi-modal wide-area transportation simulation model of Hastings and Havelock North, New Zealand, built on behalf of Hastings District Council. This model formed a key element in Hastings District Council’s successful bid to become the New Zealand Transport Agency (NZTA) Model Community for walking and cycling, for which they have been awarded $3.5m funding. The analysis undertaken using the simulation model was essential for the economic evaluation of the potential benefits of implementing cycling and walking schemes in and around Hastings. This paper provides a link between the what, how and why of designing a methodology for sustainable integrated land-use transportation modelling

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