The prevailing practices of pavement design today typically handle the structural and functional design separately in a fragmented piecewise manner. In meeting the modern day requirements to provide efficient, safe, quiet, durable and environmentally sustainable pavements, there is a need to adopt a holistic approach in pavement design to address the structural and functional requirements in an integrated manner. This paper first identifies the aspects of current design practice that needs to be improved, and then proposes a framework for pavement design to address both the structural and functional requirements in an integrated systematic approach. As an illustration, this paper presents a pavement design framework to cover both the structural design of a pavement to satisfy structural requirements for a design traffic loading, and functional design that addresses the following aspects: the minimum skid resistance required for safe wet-weather driving, the maximum tire-pavement noise permitted for control of traffic noise level, as well as the considerations of environmental sustainability.
Porous pavements are often used as a means to improve skid resistance during wet weather. During the design and construction phases, porosity is often used as the single parameter representing porous pavement drainage capacity. However, it is insufficient to use this parameter to predict frictional performance on porous pavements because pavement mix with different aggregate sizes and yet having identical porosity values can yield significantly different skid resistance behaviors. This paper presents a numerical framework to analyze the influence of aggregate size on porous pavement skid resistance. It was found that despite having identical porosity, pavement mix with larger aggregates can provide higher permeability value, which consequently reduces the water film thickness on the pavement surface under a given rainfall intensity and relieves the hydrodynamic pressure buildup underneath the tire. Porous pavements constructed with larger-size aggregates for a given porosity are found to exhibit better skid resistance performance.
Porous asphalt concrete (PAC) is mainly applied to the surface drainage layer on high-speed trafficked highway pavements. The use of polymer-modified binder was shown to minimize the abrasion loss and enhance the durability of the PAC mixture. Test results indicated that using polymer-modified binder compared with unmodified binder reduced rutting and raveling, with the mixture containing high-viscosity binder showing the best performance in the field. There were indications of drainage improvement by replacement of traditional binders with polymer-modified binders according to measurements in the field. PAC pavement surfaces provided good frictional characteristics once the asphalt binder film was worn from the aggregate.
The linear viscoelastic (LVE) limits and rheological properties of bitumen-filler mastics were determined using a dynamic shear rheometer (DSR). Strain and frequency sweeps were performed on mastic specimens over a wide range of test temperature and frequency conditions. The use of an empirical algebraic equation of the Christensen and Anderson model (CA model) was used to characterize the LVE rheological behavior of the mastics in this study. Test results showed that the LVE limits for the concentrated suspension mastics were more restrictive than those for the dilute suspension mastics. Filler particles were likely to cause a hydrodynamic interaction in the concentrated suspension system. A significant difference in stiffening effect for the concentrated suspension mastics was observed due to the filler effective volume as well as the interparticle interaction. For the dilute suspension mastics, the difference in filler stiffening effect was minimal irrespective of filler type in this study.
The traditional method of traffic signal design is based on the assumption of a constant queue discharge rate, also termed the saturation flow rate. However, a number of field studies conducted in Taiwan and the USA contradict this assumption because they reported a marginally increasing trend observed for the queue discharge rate toward the back of the queue. This paper reports on a field study conducted in Auckland, New Zealand at six signalized intersections. The field observations confirm the findings of previous research, namely that the queue discharge rate increases toward the back of the queue. Two empirical models are proposed to reflect the observed queue discharge behavior. One of them is implemented to calculate the capacity and signal timings. The proposed model shows the potential to overcome the shortcomings of the traditional method in practical applications.
This study investigates individual noise sensitivity to change in aircraft noise levels for residents living near Fukuoka airport, which has proposed a capacity expansion plan. To understand better peoples' perception of aircraft noise, we introduced a reference point (RP) concept into analysis of noise sensitivity. A field survey consisting of social questionnaires and an innovative headphone interview system were carried out to assess general noise perceptions, annoyance and loudness sensitivities, and indoor noise levels. Different statistical analyses including structural equation modeling (SEM) and Tobit regression were performed. It was found in SEM that there was a reduction in annoyance sensitivity due to an increase in perceived aircraft noise level. Further, results from Tobit regression-based RP indicated that people are more sensitive to decrease in noise level than they are to an increase. Being less sensitive to a larger aircraft noise implies an escalation in noise-accustomed levels.
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