I refer folks to John Allen's bike blog, to the post "When Slow is Too Fast" and the embedded video of a crash. I've seen this situation develop more than a few times on Diamond, when headed southbound between Orange/Sandia and West Road. Rush hour traffic can back up there and cyclists in the bike lane can be passing slowed traffic in the two lanes (and left turn bays) on their left. Meanwhile, northbound motorists can be turning left into Metzgers, the donut shop, UNM-LA, or at several other locations, which creates potential conflicts with thru bicyclists who may be screened from the turning motorist's vision. I was nearly knocked off the BMW in that scenerio, only saved by my curiosity of "gee, I wonder if someone is about to turn left in front of this stopped school bus".
As I mentioned on John's blog, the telltale in the video to watch is there is a break in traffic at the curbcut. One can assume a possibility the drivers are allowing left turning traffic to turn by creating the break. The cyclist moving forward is screened from left turning cars by stopped traffic, especially that big, black SUV in the rightmost travel lane.
In light of the last two blog posts, this would obviously be a good time to wear a helmet. But a helmet wouldn't do much for this guy's collarbones, hands, or knees. Heightened situational awareness and training in an emergency stop might have avoided the crash.
Take a look over to John's blog. Be nice to get all comments in one place.