Special highway design to promote connectivity Secondary Roads and access to the area

Abstract

This study aims to investigate various forms of ramp connections between a motorway and other secondary highway corridors.  Kanchanaphisek West Ring Road Intercity Motorway (Bang Khun Thian – Bang Bua Thong) is used as the case study. It is found that highway design in the U.S. usually employs grade-separated interchanges to provide direct linkage.  On the other hand, highway design in Thailand prefers connection through frontage roads before approaching toll plazas. Such connection separate local traffic from high-speed mainline traffic. Meanwhile connection between the motorway and large highways still relies on grade-separated interchanges to facilitate all possible movements. At the opening year 2026, it is forecasted on the base case that 187,077 vehicles will enter the system each day, with an average annual growth rate of 1.69% between 2026 and 2056. The 10+1.50 baht per kilometers fare structure is proved to generate maximum revenue. This project requires 68,504.03 million baht of investment throughout the 30-year project life. An economic benefit analysis shows that the locations and types of ramps and interchanges are appropriately designed which generate benefits on time saving, vehicle operation cost saving, and accident reduction.  All key indicators are above the minimum standard which means that the benefits from this project are worthwhile compared to investment resources and opportunity cost that must be spent.

                Traffic engineers with experience on grade-separated interchange design point out that ramp and interchange design must give priority to safety first, followed by traffic handling capacity and driving maneuver difficulty.  Finally, they suggests that the most appropriate forms of ramps and interchanges for motorway in Thailand are Pinavia interchange and frontage ramps.