GUIDELINES FOR THE USE OF PROTECTED/PERMISSIVE LEFT-TURN PHASING

A study is reported which attempted to develop guidelines to aid traffic engineers in deciding whether permissive left-turn phasing is appropriate for use at a given location. A literature review was made, a survey of highway district traffic engineers was conducted to locate intersections with permissive phasing, and before-and-after accident data were collected. The results are given of the inventory and the accident analysis, and recommended guidelines are presented. It is noted that protected/permissive is the preferable method of left-turn phasing because of savings in time compared with protected-only phasing. However, there is an associated increase in accident potential, and conditions under which it should not be used are listed.