A single lane
in the center
of a highway
used solely for making left turns
from either direction of traffic.
Sounds like a great idea, but it's one of the few times in United States automobile travel when the normal flow of traffic puts you in the same lane as a car going in the opposite direction. Now, if everyone's paying attention, and the entrances to stores or homes are positioned properly, no problem, but this does not have to be the case. Thus the idea that you're taking your life into your own hands.
Suicide lanes are often also used as on ramps by idiots who are making left turns from a parking lot onto the road. This is wrong. The lanes are for left turns from the main road only. If you can't make it clean without using the suicide lane, don't turn.