號誌化路口衝突左轉車道之疏解行為相當複雜，但國內之相關研究並不多。本研究將衝突左轉之疏解行為解構為先行左轉、強行左轉、利用間距左轉及燈號轉換期間左轉等四項主要行為，迴轉行為暫未納入分析。本研究利用了11個衝突左轉車道之錄影資料，輔以22個車道探討先行左轉行為，進行各項基礎之交通行為分析。透過現場資料分析，本研究分別探討臺北市與臺北市以外之其他地區的各項疏解行為特性，並進行比較分析，結果發現：(1)臺北市先行左轉之情形很少，其他地區較多；(2)其他地區強行左轉之週期百分比亦明顯高於臺北市；(3)臨界間距之大小在郊區路口有隨對向車道數之正向關係，但臺北市之資料則無明顯關聯；(4)臺北市於燈號轉換時段能疏解之車輛數平均為2.9小車／週期，但郊區沒有適當的觀測值。進一步衡酌臺北市交通負荷較重而其他地區一般交通負荷相較低，此特性可作為前述行為之合理解釋。

The behavior of opposed left turn traffic at signalized intersections was complicated. However, there were scarce researches about opposed left turn in Taiwan. Opposed left turn behavior in this study were decomposed as four major parts: leading-left-turn, forced opposed-flow left-turn, gap acceptance left-turn, and change interval left-turn. This study tried to analyze the basic behavior by field data collected on 11 opposed left turn lanes and 22 leading-left-turn lanes. Moreover, the behavior of Taipei city were compared with those of other city. There were four major findings in this study. (1) Leading-left-turn behavior were very seldom found in Taipei, but those were often found in other cities. (2) The probability of vehicle forced opposed-flow to left turn in other cities was significantly higher than those in Taipei. (3) The acceptance gaps to left turn was alike positive related with the number of lanes in opposed flow at suburban signalized intersections, however, there were no significant relationship for the signalized intersections in Taipei. (4) The discharge vehicles on signal change intervals were about 2.9 vehicles per cycle in Taipei. The above-mentioned different behavior at signalized intersections between in Taipei and other cities could be explained by different traffic situations, that is, the traffic of Taipei was always heavier than that of other cities.