Is a lane change without signal always illegal? I know that it almost certainly make you liable for any resulting accident, but I'm not sure that it is universally illegal.
> 142 (1) The driver or operator of a vehicle upon a highway before turning (...) from one lane for traffic to another lane for traffic (...) shall first see that the movement can be made in safety, and if the operation of any other vehicle may be affected by the movement shall give a signal plainly visible to the driver or operator of the other vehicle of the intention to make the movement. R.S.O. 1990, c. H.8, s. 142 (1).
That said there's zero cost to doing so regardless of whether other drivers are affected.
It could be one of those "if a tree falls in the forest" scenarios. If a cop is near enough to see you not signal, he could easily argue that he himself might have been affected by the turn or lane change.
Yes, failure to signal is a traffic violation. At least everywhere I've lived/traveled in the US. It's also a rather convenient excuse for police to "randomly" pull you over (I've been pulled over by Chicago PD for not signaling for a lane change, despite actually having done so).
I have no idea, but the point wasn't so much that the lane change is illegal, but that lack of signal is used to indicate lack of driver attention. I shouldn't have used "illegal" in my original post.
