This article aims to analyze the effect of median U-turns and estimate the capacity of primary highways in Thailand using a traffic micro-simulation model. Six-lane and four-lane primary highways were selected for the study. The base condition results determined that the maximum capacity of a six-lane primary highway was 2,130 passenger cars/hour/lane, while the four-lane primary highway capacity was recorded as 2,194 passenger cars/hour/lane. Both results were slightly higher than those of the HCM2010 approach. Under prevailing conditions, both sections exhibited lower capacities than the HCM results by approximately 33.7% and 19.8% for the six-lane and fourlane primary highways, respectively, causing the impact of the median U-turn and highway characteristics in Thailand to directly affect traffic and driving behavior. Using the micro-simulation results, an equation was also regressed for estimating the capacity resulting from the impact of the median U-turns and heavy vehicles. These results may be used as guidelines for the design and analysis of multilane highways in Thailand.

The objective of this research was to evaluate the efficiency of the motorcycle-specific pausing zone under the Bike Box Project (BBP). This zone is designated at the very front of the waiting line for the traffic light. The indicators used to measure the efficiency comprised the lost time when starting up at the beginning of the green light, the change of the proportion of the motorcycle pausing points, the accident statistics, and the worthiness for investment. Two intersections in urban areas were used for the analyses and evaluation, which were carried out to compare between the period prior to and after the project began. The study indicated that after the project began, the start-up lost time could be reduced by roughly 31-46% during peak hours, with approximately 73-78% of motorcycles pausing in the green zone (Bike Box Zone). The number and severity of the traffic accidents after 1-year of BBP implementation significantly decreased. The results of the study showed the efficiency of traffic management, safety, and worthiness for investment. It is thus appropriate to extend the project to other areas in the country and abroad, especially in urban areas where motorcycles are greatly used.

This article purposed to present the maximum capacity and to develop the equation in the capacity estimation of 4 types of four-lane highways by using the micro-simulation model. Regarding the analysis, the factors affecting the capacity include access-point, heavy vehicles and median u-turn. According to the study, it was found that the maximum capacity of the four-lane highways in type 1 is 2194 passenger car/hour/lane. In the descending orders, the maximum capacity of the highways with four lanes in type 2, 3, and 4 are 2161, 2094 and 2017 passenger car/hour/lane, respectively. At the same time, the maximum capacity of the prevailing condition in the study is 1300-1600 vehicles/hour/lane, which is different from the HCM2010 method for 20-30%, due to the Thai's highway characteristics directly affect the traffic and driving behavior. Median u-turn affects the four-lane highways in type 1 and 2 the most, while access-point factor has the most influence towards type 3 and 4. In addition, the author has developed the equation models for capacity estimation, which the result derived from the relationship between the capacities and affecting factors. It was aimed at using as the guidelines in the capacity assessment of Thai's four-lane highways in the future.

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The effect of motorcycle and shoulder width on two-lane highway capacity using a traffic micro-simulation model was investigated, together with other effect factors, which are heavy vehicles and access points. Four sections of a two-lane highway that have different shoulder widths were selected for the study. Under prevailing conditions, a two-lane highway with a shoulder width of fewer than 1.5 meters will cause a motorcycle to interfere with the carriageway and other impact factors that make capacity significantly less than HCM2010 calculation. The analysis of the base conditions model determined that the maximum capacity of a two-lane highway with a shoulder width of 2.0 meters was 1979 passenger car/hour/direction. Two-lane highways with shoulder widths of 1.5, 1.0 and 0.5 meters recorded maximum capacity at 1914, 1860 and 1789 passenger car/hour/direction, respectively, with all results higher than the HCM 2010 calculation. Model equations for capacity estimation were developed using multiple linear regression analysis derived from the relationships between capacity, shoulder width, and other affecting factors. Results can be used as guidelines for the future capacity assessment of two-lane highways in Thailand.