[lubujackson]

There is very specific clumping behavior on the I5 in Northern California I've noticed. It is a long, 2 lane highway often used by truckers. It tends to be fairly congested but not ever backed up.

What I see every time I drive it is a new clumping behavior that emerges: some big rigs tend to drive quite slow but do that thing where they want to pass someone going 54 and they are going 55 so it takes ages and the traffic in the left lane gets longer and longer, leaving a gap in the right lane.

At thing point, some drivers say "fuck it" and zip down the right lane and aggressively merge back in to shorten their wait getting around the blockage. As you are likely driving this route for hours (SF to LA) you see it happen more and more often and it becomes more and more prevalent. I find it exhausting because there is no way to veg the whole drive unless you are the slowest car out there because at best someone is going to jab in front of you at the last second and you have to mash you brakes to avoid them.

The interesting thing is that this is always how the traffic flows on this road, and nowhere else. It must be a precise combination of traffic levels, lanes available, traffic mix, differring speeds and even average distance travelling, so people notice and feel compelled to respond to the pattern.

[jrootabega]

In my experience, anywhere there is heavy semi truck traffic will have significant problems once there are enough cars around ("enough" being far less than it should be). 2 lanes, 3 lanes, 4 lanes, hills, it's all bad. But yeah, only 2 lanes per direction makes it comically awful. Happens on sections of I-81 too.

I think the specific pattern you're talking about happens because when a truck is passing slowly but infrequently, it makes some sense to be polite and line up behind it. When trucks are passing so frequently, and so incredibly slowly, being polite is useless. There needs to be a zipper merge happening behind the truck being passed. But the left lane people feel they've paid their dues by waiting in line, and half the right lane people don't even care. The right lane people also stay so close to the truck in front that they can't safely merge left at highway speeds anyway. People also tend to not fill back in to the right lane between truck passes. I'm not sure that would even help, but it does make people who do seem like cheaters to the people who refuse to.