STATISTICAL ANALYSIS OF VEHICULAR LOADINGS ON SINGAPORE ROADS

Abstract

This thesis presents a statistical analysis of vehicular loadings of Singapore roads. The study involves field surveys of vehicular loading and traffic volume. The main objective is to develop statistical models for estimating design axle loadings for road pavements in Singapore.Roads and road vehicles were classified into 5 and 9 classes respectively in the analysis. Data collection methods employed in this study were manual counting. Automatic recording using automated traffic counter, automatic recording using traffic classifier, weigh-in-motion system and video recording. The characteristics of heavy-vehicle and the design lane heavy-vehicle volume models were studied. Two different forms of volume model were studied, one based on lane use characteristics of heavy vehicle traffic and the other based on design-lane traffic composition.Weibull distribution was found to be suitable in describing the distributions of heavy-vehicle weights among the five probability distribution models tested, namely the exponential distribution, Weibull distribution, gamma distribution, lognormal distribution and Erlang distribution. The polynomial regression models and power models were developed by vehicle types to predict axle loads from a given gross heavy-vehicle weight. A simulation programme was developed to obtain estimates of the daily axle load factors. In the programme, a total directional volume was generated randomly based on the actual survey data for each road section. All the statistical models developed in this analysis were then applied in the simulation analysis for the estimation of axle load factors.The simulation results show that single-unit trucks have the highest relative damaging effects on roads in Singapore. Among the tractor-trailer combination trucks, the 3-axle and 4-axle trucks are significant contributors to road damage. The results also show that the overall traffic stream load factor is the highest on expressways followed by major arterials, collectors, local industrial estate roads and local housing estate roads in descending order.