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Comment by streetfighter64 | Hacker News Reader

> The signaler needs to have anticipated it and not signaled until this problem doesn't exist

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

It's not the responsibility of the car changing lanes to optimize the fuel economy of the cars behind, but it is the responsibility of the cars behind to not needlessly impede other drivers from getting where they need to go.

> When there's already a lot of momentum toward closing the gap

Does "momentum towards closing the gap" just mean that you're keeping a higher speed than the car in front of you? I don't see any reason you'd do this unless you have another free lane to the left and are planning to pass. If you don't then you're just reducing your margins to the next car for no reward, as you'd have to slow down anyway once the gap is "closed".

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> 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.

> 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.

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

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...

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.

> 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).

>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?

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.

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!

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-...

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

If I see that someone is actually changing lanes (in terms of lateral position changing within their lane) then of course I would get out of their way, as it would be unsafe not to. But if they're postponing their lane change (despite their signal already being on) because I'm about to be in their way, that's the scenario I'm talking about when I say I'm going to continue on my way rather than lose momentum/fuel: they are waiting for me to not be in their way, they will continue waiting until I'm gone, and they should've waited until I'm gone before signaling (by "should" I simply mean if they want to assimilate into this driving style). The example scenario in my other recent comment will help illustrate this.

> leave a big enough buffer with the car in front of you [...] leaving a healthy gap

I realize that my original comment wasn't clear on this, but the "gap" I'm talking about is between cars in different lanes (again, see the example scenario in my other comment). We can assume no lead car at all.

> 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 won't say it's the best, it's just what I've noticed. But it's not "their path" if they're just hoping to be let in without actually moving. When they start moving, it's a whole different story, and I would get out of there (ideally lane change, but brake if needed). I guess "stealing my attention" would've been a better way to say it than "scare."

I think if you're waiting for them to actually start to change langes before responding, then you're leaving too much up to chance. Because if you go to pass them they might start to merge when you no longer have any safe options available - either because they didn't see you, they misjudged, they're just an a-hole, etc. There are a lot of unpredictable drivers out there.

I think the safest thing - and the most polite - is when they first start to signal, make a determination if you are able to safely give them space by easing off the gas and maybe lightly tapping the brakes (of course you don't want to do any hard braking because that creates a risk of being rear-ended). And if the answer is yes, then let them merge. If you're traveling at a safe speed, leaving a safe distance to the car in front of you, and assuming they signal about the time the car in front of you passes them, this should be doable more often than not.

Indeed, the extremely minor inconvenience of creating a gap in that scenario is very common even in the northeast US. It's the other half of the spectrum, where it's a more severe inconvenience, that it's uncommon for a northeastern driver to accommodate, from which the perception arises that we fight people who are signaling. The signaler is the one picking the fight, and we simply don't entertain it.

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