Highway efficiency improvement : Thailand´s route no 4 - Case study

Abstract The economic growth in Thailand has spread from the metropolitan area to other region of the country. This has led to the development of regional highway to serve as the connection link between the main port city, Bangkok and other part of the country. However, the project did not foresee the population growth situated along the highway. New dwellings on roadside are common throughout the highway. This increase demand for accessibility to the highway results in disruption of the main traffic flow by the local traffic. Thus these communities have contributed to the traffic problem on the highway. One of the most severe situations occurs on regional highway route no. 4. The link acts as a feeder from the metropolitan area to the southern region. The traffic composition on route 4 comprises of private vehicles such as cars and motorcycles and commercial vehicles such as buses and trucks. This study chosen a critical segment on route 4 where congestion problem has been escalating and potential crisis seems certain. The road section for investigation comprises of 3 lanes highway and 2 lanes frontage road (one way). This section has 2 traffic lights locate less than 2 kilometers apart and 2 hyper markets situated along the roadside. The congestion is mainly the result from the traffic light pile-up, mix traffic (local traffic) and at grade U-turns. Two design alternatives are proposed; flyover and compact interchange scenario. New design alternatives are simulated in the micro traffic simulation software, S-Paramics. The future demand of the year 2014 and 2019 are simulated in the new scenarios as well as the existing one (do nothing scenario). The highway efficiency improvement is evaluated by comparing the following measure of performances: speed, travel time and queue length with the do nothing scenario. Both alternatives solve the traffic situation by removing the traffic light from the main road. This result in an improvement in all MOPs considered. The compact scenario proves superior to the flyover scenario. This became more apparent in the simulation for 2019 where the speed efficiency increases by 59%, travel time decreases by 70% and the queue length lessen by 79%.