[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).