The Development and Assessment of Free-Flow Speed Models under Heterogeneous Traffic in Facilitating Sustainable Inter Urban Multilane Highways

Lee Vien Leong,Mohammed Bally Mahdi,Wins Cott Goh,Tuti Azmalia Azai

doi:10.3390/su12083445

Lee Vien Leong, Mohammed Bally Mahdi + Show 2 more

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https://doi.org/10.3390/su12083445

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Abstract

The desired speed that drivers can drive without being obstructed or influenced by other road users is characterized as free-flow speed. However, free-flow speed can be influenced by other factors such as the characteristics of the vehicle, driver, road conditions, weather, and speed limits. Due to the country’s heterogeneous traffic conditions, this study aims to develop and assess free-flow speed models based on different vehicle classes and road characteristics in Malaysia. Data were sampled at 16 sites of multilane highways in Malaysia. Analyses of free-flow speed were conducted based on individual and grouped vehicle classes. Subsequently, multiple regression analyses were conducted based on these grouped vehicle classes to develop free-flow speed models. The findings show that the model with the grouping of all vehicles, which includes heavy vehicles and motorcycles, is the most suitable model as it yields the best results based on the performance indicators. The development of a free-flow speed model based on local traffic conditions, which can accurately estimate free-flow speed without having to conduct field measurements, is essential for saving time and costs in data collection. The findings from this study will contribute to improving the design of multilane highways and, ultimately, ensuring the sustainable environment of road networks.

Highlights

Multilane highways are highways with more than one lane in each direction
Assessments of the mean free-flow speed according to vehicle classification were conducted
This study, which is part of the Malaysia Highway Capacity Stage 3 to produce the Malaysia Highway Capacity Manual, is a continuous effort by the Ministry of Works Malaysia to ensure that the future designs of highways are sustainable and that analyses of transport infrastructure are made accurately and are representative of local conditions

Summary

Introduction

Multilane highways are highways with more than one lane in each direction. These highways can be undivided or divided. In Malaysia, these highways usually have two lanes in each direction and are typically located in suburban communities that lead into central cities. They may extend along high-volume rural corridors, connecting two cities or two significant activities that generate a substantial number of daily trips. According to the Malaysian road geometry design guidelines [1], urban areas are defined as areas with a population of at least 10,000 people, where buildings and houses are gathered, and business activities are prevalent. The R5 standard is the design standard for roads, provides a high geometric standard, and usually serves long to intermediate trip lengths with high to median traveling speeds and partial access control [1]

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