> How do you handle an upcoming left turn (assuming right hand driving) during heavy traffic?

If I am in the middle lane (lane 2), and I realize I need to get into the leftmost lane (lane 1) to make a turn, but lane 1 is too full for me to simply move into it without affecting others, then I would have no choice but to cut someone off. I would minimize the effect in two ways: by trying to cut off whoever has left the largest gap in front of them (hunting for a gap that might not be the largest now, but will be the largest when I actually use it), and by assuming as much of the rear-end-collision risk as possible until the lane change is complete. Only once my position is optimized to begin the lane change would I signal, because signaling from a suboptimal position could scare people (or give them an opportunity to fight my ability to change lanes). If I can remain in the optimal position for a couple of blinks without any downside, I absolutely will, but in the very heavy traffic we're discussing, typically the tires hit the lane line between first and second blink -- very much not an "ask."

> Does "momentum towards closing the gap" just mean that you're keeping a higher speed than the car in front of you?

No, I was referring to the gap between the car signaling for a lane change and the car that ends up preventing the lane change, which are in two different lanes. Suppose I'm in lane 2, and a car is in lane 1 a few car-lengths ahead of me. Suppose the car in lane 1 is going slower because they just merged from a left-side entrance ramp. Due to our speed difference, after a moment they're now only 2 car-length ahead of me. Their right turn signal comes on. Now they're 1 car-length ahead of me but they haven't yet changed lanes. Now they're 0 car-lengths ahead of me (i.e., the gap is closed) and cannot change lanes. I did not "let them in" upon seeing their signal, because that would ruin my momentum.

Also really strange to me to be prioritizing fuel economy over safety.

And anyway, it's more fuel efficient to leave a big enough buffer with the car in front of you so that if they slow down, you can just take your foot off the accelerator to match speed rather than braking. And increase speed again slowly when they speed up (again leaving a healthy gap). For anyone driving a hybrid or EV especially much of those losses can be recovered with regenerative braking.

The other thing is that in places where people use turn signals properly, it's customary to signal a few seconds before you turn (where I live the law is to signal at least three seconds before changing lanes). That gives people plenty of time to ease off the accelerator and make space without needing to hit the brakes.

I also can't comprehend how if you're "scared" by someone signaling when you are in their blind spot, the best course of action could be to put yourself directly in their path vs giving a little extra space to safely merge.

I think the more likely explanation is just that this anti-social behavior has been normalized in the North East. And drivers are either oblivious to others around them, or have adopted the outright aggressive attitude that yielding to other drivers makes you a sucker.

To their credit, traffic fatalities do tend to be lower in the North East than the rest of the country on both a per-capita and per-mile-driven basis [1]. But I suspect it has more to do with other factors like lower speed limits than merging behavior. And this is supported by the fact that Massachusetts (and the most of New England) has the highest per-capita accident rate in the country [2].

So not only are you adding to each other's stress levels. You're also driving up insurance prices and contributing to traffic jams with more accidents.

[1] https://www.iihs.org/research-areas/fatality-statistics/deta...

[2] https://www.visualcapitalist.com/mapped-u-s-states-with-the-...