At signalized intersections, permitted left turns (i.e., on a green ball, after yielding) across multiple through lanes and across a separated bike lane or bike path present a threat to bicyclist safety. A conflict study of two such intersections with a bidirectional bike path found that when cyclists cross while a vehicle is ready to turn left and there is no opposing through traffic to block it, the chance of the left-turning motorist yielding safely was only 9%, and the chance of their yielding at all—including yielding only after beginning the turn, then stopping in the opposing through lanes—was still only 37%. Motorist non-yielding rates were worse toward bikes arriving during green, toward bikes approaching from the opposite direction (i.e., riding on the right side of the road), and toward bikes facing a queue with multiple left turning vehicles. Of 112 cyclists who arrived on green when there was at least one left-turning car, but no opposing through traffic blocking it, 73 had to slow or stop to avoid a collision. Although these conflicts could be essentially eliminated using protected-only left turn phasing (turn on green arrow), common existing criteria prefer permitted left turns to reduce vehicular delay. A case study shows how, by considering multiple signalization alternatives, it can be possible to convert left turns to protected-only phasing without imposing a substantial delay burden on vehicles or other road users.

在有信号灯的十字路口，允许左转（即在绿色球上，让行后）跨越多条直通车道和跨越单独的自行车道或自行车道对骑自行车者的安全构成威胁。对具有双向自行车道的两个此类交叉路口进行的一项冲突研究发现，当骑自行车的人在车辆准备左转且没有对面来往的车辆阻挡时过马路时，左转的驾车者安全让行的几率仅为 9% ，而且他们完全让步的机会——包括只在开始转弯后让步，然后停在对面的车道上——仍然只有 37%。对于在果岭期间到达的自行车、从相反方向驶来的自行车（即在道路右侧骑行），驾车者的非让步率更差，和面对多辆左转车辆的队列的自行车。112 名骑自行车的人在至少有一辆左转汽车时到达果岭，但没有对面的交通阻塞，其中 73 人不得不减速或停下来避免碰撞。尽管可以使用仅受保护的左转相位（打开绿色箭头）从根本上消除这些冲突，但现有的常见标准更喜欢允许左转以减少车辆延迟。一个案例研究表明，如何通过考虑多种信号化替代方案，将左转转换为仅受保护的相位，而不会对车辆或其他道路使用者造成实质性的延误负担。尽管可以使用仅受保护的左转相位（打开绿色箭头）从根本上消除这些冲突，但现有的常见标准更喜欢允许左转以减少车辆延迟。一个案例研究表明，如何通过考虑多种信号化替代方案，将左转转换为仅受保护的相位，而不会对车辆或其他道路使用者造成实质性的延误负担。尽管可以使用仅受保护的左转相位（打开绿色箭头）从根本上消除这些冲突，但现有的常见标准更喜欢允许左转以减少车辆延迟。一个案例研究表明，如何通过考虑多种信号化替代方案，将左转转换为仅受保护的相位，而不会对车辆或其他道路使用者造成实质性的延误负担。