Lee Vien Leong

The Alternative Trip Generation Model for Flat/Apartment/Condominium and Low Cost Housing Subcategories

Malaysian Trip Generation Manual (MTGM) is an important document to assist transport planners in forecasting the estimated trip attraction and trip production from a land use. The forecast is crucial in estimating trip generation from a proposed development on the existing road network. Therefore, this study is to verify the accuracy of the existing trip generation model published in MTGM for flat/apartment/condominium and low cost housing subcategories. By applying variable transformation, four alternative models were developed. They were the logarithmic model, the inverse model, the linear-logarithmic model and the logarithmic-linear model. Using residual analysis, influential data was identified and taken out for second analysis. Model selection was based on R2 value, t-test and Kolmogorov-Smirnov test results. Besides linear model, logarithmic model is also truly representing trip generation model for both subcategories. There is some difference in the trip generation estimation between the study model and the existing model in MTGM. Sensitivity analysis shows the level of sensitivity between study model and existing linear model. One of the implications in using the studied trip generation model is in evaluating level of service of the junction.

Assessment of Queue Length and Delay at Toll Plaza Using Microscopic Traffic Simulation

Highways and freeways usually experience severe traffic congestion due to the presence of toll plazas which is considered as a bottleneck. In recent years, traffic engineers around the world have utilised microscopic traffic simulation models as tools to evaluate the performance of selected freeway facilities based on known traffic pattern data. This study attempts to analyse the performance of toll plaza by utilizing the microscopic traffic simulation software VISSIM 6.0, based on two different output measures, namely: average queue length and average delay time. At the selected toll plaza, data are collected at toll booths for all three modes of payments, which are: cash mode, Touch n Go, and Smart TAG. Therefore, this study aims to build a microscopic traffic simulation model that is capable of analysing the behaviour of vehicles at toll plaza based on the mentioned output measures for each mode of payment and also to determine the type of payment mode that has the most significant impact on the overall performance of toll plazas and ultimately, to understand the causes of congestion at toll plaza.

Volume-Delay Function in Trip Assignment

Four-stage demand models are the most popular travel demand forecasting models. Trip assignment which is the last stage in the four-stage demand modelling is a key element in travel demand forecasting process. Traffic assignment model is used to assign travel demands into the road network and predict network flows that are associated with future planning scenarios based on the estimates of link travel times. In order to calculate travel time between origin and destination, a function presenting the relationship between link delays and link flows is used. This function is known as Volume-Delay Function (VDF) and it is the fundamental component of equilibrium trip assignment models. This study aims to investigate and improve VDFs for heterogeneous traffic at different type of arterial roads in Malaysia by using the road network in Balik Pulau, Penang as a case study. Primary data such as traffic volume and speed are collected at three types of arterial roads, which are the principal arterial, minor arterial and collectors to derive the parameters required in the VDFs. In this study, the most well-known and most widely-used volume-delay function which is known as the BPR function developed by the U.S. Bureau of Public Roads was investigated and calibrated using the transportation planning software, EMME 4.1.3. The calibrated functions are then validated with field data. The output from this research is very important as better understanding of VDFs can produce better estimate of link travel times and hence better planning for future scenarios.