TRAFFIC AS A DESIGN VARIABLE FOR RESIDENTIAL STREET PAVEMENTS

The available information suggests virtually all traffic loading studies to date have concentrated on highways and neglected residential streets. This study sets out to quantify cumulative traffic in residential streets in terms of equivalent standard axles (esas) for use in pavement thickness design. For the purposes of analysis, traffic loading in residential streets was divided into four groups: service traffic, construction traffic, bus traffic and garbage collection traffic. Service traffic was quantified by a visually based commercial vehicle (cv) survey which rationalised all cvs into four groups: that is two axle rigid trucks with tare mass less than 3 tonnes, two axle rigid trucks with tare mass greater than 3 tonnes, three axle rigid trucks with tare mass greater than 5 tonnes, and semi-trailers. For each cv group and for each 25 per cent net load increment an estimate of esa per pass was calculated to determine traffic loading in terms of esas. The results show that per cent cv and esa per cv are on average relatively constant and independent of traffic volumes, whereas figures for esa per day vary with traffic volume. For construction traffic, bus traffic and garbage collection traffic a 'scenario' analysis was developed and resulted in simple design formulae. The relevance of cumulative traffic loading in the prediction of pavement performance is questioned, particularly for low volume residential streets where factors such as single overload and climatic environment may have a significant influence on the deterioration of residential pavements. (Author/TRRL)