To keep traffic flowing safely and efficiently, while still providing access to properties abutting main roads, many main roads in cities and towns across Canada and the USA have five lanes: two lanes in each direction plus a fifth centre lane reserved for vehicles turning left.
“Two-way left turn lanes” [2WLTL], also called, “Centre left turn lanes”, have solid and broken yellow lines on both sides, solid on the outside and broken on the inside. In addition they have pairs of white curved arrows on their road surface, showing the paths of two vehicles turning left in front of each other. Two-way left turn centre lanes are also indicated by the road sign, "Centre Lane For Left Turns Only". This sign always has a pair of curved arrows showing the paths of two vehicles turning left in front of each other.
2WLTL are designed to allow for simultaneous left turns by vehicles traveling from both directions. This has earned them the nickname, “suicide lanes.” In theory, they enable traffic to move more efficiently in the outside through lanes, increase the capacity of the through lanes and reduce rear-end, left-turn, and sideswipe collisions. As an “extra” lane, 2WLTL can also be used in emergencies by regular traffic and by emergency vehicles to bypass accidents and stalled vehicles.
When using the 2WLTL, signal your intention to change into the 2WLTL, check for oncoming vehicles in the 2WLTL, and when it is safe to do so, enter inside the 2WLTL completely. Stop in the 2WLTL until a gap in the oncoming traffic allows you to complete your left turn.
Sharing the 2WLTL safely with oncoming vehicles involves paying the utmost attention to the traffic flow and being unfailingly courteous. The right-of-way rules are dictated by the design and because the speeds involved are low, conflict is minimized. The first turning driver in the lane goes first.
When a road has a 2WLTL, left turns are not allowed from other lanes, and U-turns, if permitted, must be started from it. 2WLTL must not be used for any other purpose such as passing through any intersection or overtaking another vehicle. Some jurisdictions expressly limit the driving distance in these lanes to a maximum of 200 feet.
One challenging issue is using the 2WLTL while making a left turn onto the main road from a side street. This maneuver may arguably be illegal in British Columbia, and in any case, should be discouraged. It requires the utmost care and attention. In jurisdictions where it is allowed, it would appear that a “rolling merge” from the 2WLTL into the flow of traffic from the right is generally illegal. The requirement seems to be that you must stop once you’ve made the turn into the 2WLTL, then shoulder-check and merge right when safe to do so. This creates a supreme danger of vehicles following behind (making the same turn in busy traffic) colliding with the rear of your vehicle.
Wherever you are, do not use the 2WLTL for a left turn from a side street onto a main road. Enter the main roadway at an intersection equipped with a left turn light.