![]() The average delay for all left-turning vehicles on the approach is at least 35 seconds during that same peak hour.There is a minimum left-turn volume on the approach of greater than two vehicles per cycle during the same peak hour and,.The total delay to all the left-turning vehicles on a crucial approach equals or exceeds two vehicle hours during a peak hour and,.Separate left-turn phasing may be considered if Further study of the intersection is recommended, including review of other potential solutions. Volumes meeting these levels are only an indication that a left-turn phase may be justified. The left-turn volume is greater than two vehicles per cycle during the same peak hour period.The product of the left-turning and opposing through volumes during the peak hour exceed 100,000 on a four-lane street (2 approach lanes), or 50,000 on a two-lane street (1 approach lane) and,. ![]() Separate left-turn phasing may be considered when: These three criteria are used in numerous States, including Washington, as warrants for the installation of separate left-turn phases at a signalized intersection. The three left-turn phase criteria presented below are the result of considerable research and study. ![]() Potential solutions may include prohibiting left-turns and geometric improvements. While phases for protected left-turning vehicles are popular and commonly requested, other methods of handling left-turn conflicts also need to be considered. ![]() Pedestrian delays may be increased and due to the increased delay, pedestrians may elect to ignore the pedestrian signals. Left-turn arrows also result in longer cycle lengths, which in turn have a detrimental effect by increasing stops and delays. However, this is done at the expense of the amount of green time available for through traffic and will usually reduce the capacity of the intersection. Left-turn signal phases facilitate left-turning traffic and may improve the safety of the intersection for left-turning vehicles. ![]()
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