[hunter2_]

> 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.

[freetime2]

> Suppose the car in lane 1 is going slower because they just merged from a left-side entrance ramp.

Just to clarify, my original post was more about merging from a faster lane of travel into a slower lane, or where both lanes are traveling at about the same speed.

When merging into a faster lane I agree the slower moving car should wait for a suitable opening before signaling and merging. And there are cases where it is safer to pass a car with its blinker on than to slam on the brakes.

But also in general it's unsafe to be traveling at a large speed differential to the lane next to you. And a lot of times even though people probably could ease up a bit to make space for another car, and it would be safer to do so, they don't.

[mendigou]

The slower car should signal the moment they decide they need to merge into the lane, then wait for an appropriate gap.

[freetime2]

The Massachusetts handbook [1] says:

> Use your rearview mirror, check your blind spots, and use your directional signals when changing lanes. Remember these three steps: (1) look, (2) signal, (3) move

To me this means you don't signal until it's actually safe to merge. E.g. if a car is passing me at high speed, I wouldn't turn on my signal until after they had passed. If I did it before they pass, they might think my intent is to merge in front of them, and slam on their brakes, move into a different lane, etc.

In Japan [2] the process is 1) check rearview and side mirrors, 2) turn on blinker at least 3 seconds before turn, 3) while the blinker is on, do a shoulder check for blind spots 4) merge, 5) flash your hazards 2-3 times to thank the driver who let you merge.

So you're also checking for safety before signaling. Step 5 isn't actually required by the way but it's quite common and a nice touch I think.

These are of course cases where you have the option of moving into a faster lane at your discretion. If your lane is coming to an end, you should probably signal well before the end of the lane (although I would still wait to get up to speed before signaling).

[1] https://www.mass.gov/doc/english-drivers-manual/download Page 95

[2] https://groups.oist.jp/ja/resource-center/things-remember-pr...

[streetfighter64]

Flashing your hazards to thank somebody isn't something I've even seen officially recommended and I see it more as a nuisance in most cases. The communication can't really be unambiguously understood as a "thanks", especially not if you do it for more than one flash.

It's something I personally do about once in a hundred passes if I think somebody really went out of their way to accommodate me, but even then I realize it's detracting from road safety in several ways, such as reaching over to the often awkwardly placed button, and perhaps confusing other drivers.

But I suppose it's a cultural thing, I've heard that in India it's common to use the horn to notify other drivers of your presence even though there's no imminent danger. Which is something that in most other countries would be seen as obnoxious.

[hunter2_]

> I wouldn't turn on my signal until after they had passed. If I did it before they pass, they might think my intent is to merge in front of them, and slam on their brakes

This is precisely the point I'm making, which I perceive as more typical in the northeastern US than other parts of the US where people use the turn signal to beg for an opportunity to be created that doesn't yet exist (at which point declining to create is seen as actively fighting when it's really not).

[klausa]

>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.

...you could just miss your turn, instead of cutting someone off?

[streetfighter64]

I'm not exactly well-versed in the term "cutting someone off", perhaps it implies dangerously moving in front of somebody, in which case, obviously it shouldn't be done. But often people are unwilling to slow down to open a gap to let somebody "cut them off", even when it's perfectly safe to do so (low speeds and low speed differences).

By slowing down to let somebody in front of you, you prevent them from missing their turn at practically no cost to yourself. But there's this psychological need to be "first" among many drivers, that also causes other irrational behaviors.

It's not uncommon to see drivers keep way too little distance to the cars in front and pass quite aggressively, only for us to end up next to each other at the next red light anyway. All their wasted gas and lowered safety margins got them was arriving at the light 2 seconds earlier.

[hunter2_]

I'll admit, many maneuvers can be described as cutting someone off. One so crazy that it would likely cause a collision should never be performed, but I was talking about the low-speed "bumper to bumper traffic" scenario common in lanes dedicated to making a left turn: the reason the gaps are too small for a non-cutoff lane change is a direct consequence of the low speeds involved, say 0-10mph. Imagine cars are nearly stopped for a red light, with gaps varying between 0.2 car length and 0.5 car length (this is much tighter than other parts of the US where gaps while stopped for a red light are typically 1-3 car lengths). I would line the nose of my car to the very front of the 0.5 gap (taking the majority of the risk), signal, cross the lane line within a flash or two, forcing the gap to expand to just over the length of my car, all at just a few mph. This is the type of cutting off I was referring to. And the driver who was cut off has no opportunity to fight; they would if I signaled too early!