Vandy Vorasak creator Yordphol Tanaboriboon Chairperson Prapansak Buranaprapa Co-Chairperson Takahashi, Kiyoshi Examination Committee Pannapa Herabat Examination Committee The World Bank Scholarship Donor text series technical report th Bangkok Asian Institute of Technology 2000 continuing eng 156 leaves Traffic accidents and traffic congestion at the intersections of major roads in Vientiane are caused by improper geometric design. This research study investigated the existing conditions of the two selected types of intersection in Vientiane: signalized intersection and unsignalized intersection. In addition, proposed measures were recommended to improve the conditions of these intersections in particular the geometric design standard. In order to reach the desired objectives of the research, capacity analysis was employed and this capacity analysis is also related to geometric design. Tanner's formula and shared-lane use method are used to determine the capacity of minor approaches and left turn from major traffic stream for unsignalized intersection. Capacity of signalized intersection is determined from flow ratio method and NETSIM American traffic software. AASHTO method and Australian method (NAASRA) are also used for geometric design study. The results indicated that capacity of at-grade intersections can be increased by improvement of geometrics such as channelization and separated turning lanes. For signalized intersections, the cycle length is one factor affecting capacity. Thus, proper design of signal timing is very essential to improve the traffic flows at intersections in Lao PDR. A research study submitted in partial fulfillment of the requirements for the degree of master of Engineering, School of Civil Engineering Research Studies Project Report (M. Eng.) - Asian Institute of Technology, 2000 Roads Laos Interchanges and intersections Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B06577 http://203.159.5.9/ait-thesis/detail.php?q=B06577 031200 20260818090826.0