Let's talk a bit about left turns (this conversation assumes drive-on-the-right traffic flow). On two-way streets. Across traffic. They are undeniably dangerous. How to treat them? I think they should be broken in to four categories:
1) one lane of traffic in each direction, slow moving cars (<25 mph), not a high traffic density
2) one lane of traffic in each direction, faster cars and higher traffic density
3) two lanes of traffic (or more? how are you even biking on this street?) in each direction
4) two lanes of traffic in each direction, high traffic density
I would say that only in case (1) should you turn left at a green light across traffic without hesitation. That is to say, you'd turn left as if you were driving a car. I do this many times every day. If a car is oncoming I make sure they are also turning left before proceeding.
In all of the other cases, I don't do what I would in a car, I do what I would if I were a pedestrian. I go across the green light, going straight, as if I were not going to turn left. Then I stop at the corner or hop up on the sidewalk *slowly*, watching out for bikes and ped(estrians)s. (That's a nice word, estrian if it were a word, which it seems not to be). Then I look left and wait for that light to turn green and proceed on the street with traffic or slowly through the painted lines in the crosswalk, and proceed on my way. Hey Presto! A left turn.
What is the alternative in cases 2-4? It is to merge left into the fast moving traffic, signalling with an outstretched arm, and then turn left at the green light while moving at speed. This can work very elegantly, but it is not tolerant to error. That is to say, if you should have to slow down rapidly, if the traffic is moving to fast for you to find a break, if you should fall, if a driver (now on your right) should not notice you and merge left you are in serious trouble. And this method is barely faster than the stop and turn method in the previous paragraph.
What's my point? My point is that I see too many people doing the left turn across traffic at a green light in situations 2-4. I've done it myself. But I wish our standards of behavior were a bit different, and I wish infrastructure would support the stop and turn method. This would mean a "hop up on the curb and turn left" set of ramps on corners, or a simple, painted hook left turn system of paint like this:
http://www.theurbancountry.com/2010/11/safe-left-turns-for-bicycles.html.
Has there been discussion of such a system for left turns in Seattle? I'm not aware of it, but am probably missing it.
