I just experienced the flip side to that: the driver who won't cede space when I'm trying to merge.
I was merging legally and some guy in a pickup was barrelling along in the merge lane of the highway behind me. Instead of slowing down or moving to the left lane, he came along side me and nearly forced me off the road. Sgt. Burrows refers to the situation as follows:
There is also a duty on the driver being passed. If, while being overtaken, you choose to try to block the other driver, you could potentially be charged with “fail to assist in passing” under S. 148(7)HTA.