Originally Posted by BStill

Learned something (surprising) today. This amazes me. Encouraged/accepted by whom? Is there at least a legal limit on the speed differential when passing between cars in line abreast?

In NoVA I-95 traffic, I've never seen a motorcyclist do this in a way that even appeared to be responsible and safety-conscious. They always seem to be traveling at least +30+ mph as they zip by between cars, and I never see them coming until they are passing (startling) me. I actually see it more when traffic is moving smoothly but at/under the speed limit, more-so than stop-and-go bumper-to-bumper. (If the argument is that it would be done safer if it were legal, I think that's a stretch....)

Personally, I don't think it's safe (for either of us) regardless of the speed differential, as the mass of moving metals is just too unpredictable, and it only takes one car (which could be me) swerving at 40 mph to miss a road alligator to ruin both our days because he needed to pass me at 70 mph to save 5 minutes on his 45-minute daily commute.

The idea that one would think their riding experience with a particular area provides them with a matrix-like spidey sense to continuously sense and predict the actions of highway drivers? I sincerely wish your luck never runs out... because that's what you're really reliant on, whether you realize/admit it or not.

Even in California, I think it's a good bet that most drivers don't realize it's legal. Even if they do see you coming up behind, even slowly, I'd worry about that one ***hole that is already frustrated with traffic and life enough that he "feigns" a swerve just to mess with you.

(caveat: this is my opinion only, as I'm not a rider and never have been. admittedly, my comments are not transactionally responsive to the OP's query, but rather intended to be conversational.)