Cycle Superhighway Extension - East.

Out of interest, where are people getting the idea that these lanes would be mandatory? I can't spot it in the article.

I think the main problem is that drivers will give cyclist a lot of grief for not using the cycle lane if it is there, even if they are not mandatory and the driver is completely in the wrong.

Going along Gordon Square and Tavistock place, where there is a completely dangerous segregated cycle lane (due to cars crossing it to turn onto side roads and peds who don't look before stepping into the lane, also the lane is too narrow, so it's impossible to overtake slower cyclists), I often get grief from drivers for not using the cycle lane, even though I am traveling just as fast as they are and not "holding them up" in any way.

I can't image there will be any difference in aggressive attitude of drivers with a cyclelane extension, you can explain until you are as blue in the face as those lanes why they aren't fit for purpose, and they will still come back with "you've got a lane there, you should be in it".