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One thing that really annoys me is "elephant racing" where trucks battle to overtake at very small relative speeds (probably because they're both on their limit

One thing that really annoys me is "elephant racing" where trucks battle to overtake at very small relative speeds (probably because they're both on their limiters but one has a slight calibration advantage). Especially on 2 lane roads where they block everyone while doing so. Say a truck has a length of 16m, and starts the overtake 10m behind another one, and merges back in 10m in front. So that's an overtake distance of 36m. At 1mph relative speed, this takes 80 seconds. Meanwhile, the cars behind the truck have all had to drop out of cruise and are now doing 10mph under their preferred speed (car speed limit is 70, lorries are 60). So that 80 seconds and 10mph under is 10 seconds of overall journey time. Not enormous, but it multiplies across all the cars in the queue, and across the number of lorries making this move in a journey. However, the point is that if the overtaken lorry could just ease off the throttle by a single mph, he'd halve the overtake time, at a cost to himself of 1mph less for 40 seconds, which is less than a second of journey time. So, when overtaken, a very minor "altruistic" gesture on the part of the shower lorry pays back dozens or hundreds of times over to other road users. And that's without considering the travelling waves that linger after dozens of cars slow down from a rolling roadblock and can make the whole road slower for everyone for a long time.

vladvasiliu 5y ago
While I agree with your overall point, I think there's even lower hanging fruit that's still not picked up. In France, at least, when there are more than two lanes, basically no one drives on the rightmost lane. Yes, I know about the traffic law requiring staying in your lane if there is dense traffic. I'm specifically talking about the case when there is little to no traffic.
- adhesive_wombat 5y ago
  That's a huge issue too in the UK, especially on three lane roads and wider, where you can just sit in lane two forever, if your skin is thick enough, and everyone will just have to over- and under-take you. It's actually been illegal for some years and can get you a £100 fine, though I don't know if that's ever actually happened: you'd have to have the bad luck to encounter traffic police who do anything other than speed-gun free-flowing motorways from bridges.
ErikVandeWater 5y ago
Elephant racing could have the unintended benefit of reducing accidents (and their severity) by slightly lowering the overall speed of traffic. If elephant racing very occasionally prevents an accident due to slower speeds, it might benefit all road users as they don't have to pull over for emergency vehicles, and don't have to wait for debris to clear.
- FabHK 5y ago
  Unlikely. I think 10%+ changes in speed are much more dangerous than a 1% higher speed overall.
- sojournerc 5y ago
  What I see is definitely more dangerous. Cars stack up in the passing lane behind the passing truck. Impatient people then jump into the empty slow lane to pass the line of cars on the right, then merge greedily cutting in front of the line, making the whole situation worse.
  - midasuni 5y ago
    So drop the limit to 60 for everyone?
    - emteycz 5y ago
      Low limit for everyone leads to more accidents - drivers watch speed and try to race between speedcameras instead of riding through quickly but safely.
      - adhesive_wombat 5y ago
        Right: even with current limits, I spend a completely unreasonable amount of time glancing at the speedo, worrying about if I'm going over the limit and trying to shepherd the speed within the limit, rather than paying more attention to the traffic conditions around me. This is actually much worse on 20 roads that are converted from 30s by just swapping the signs: they were specifically designed for higher speed, so it's a constant, conscious effort to keep the speedo in mind and sight and carefully not drive to the road. I feel that this is something people didn't have to do so much: with an analogue speedo, you can't really see your speed to 2 sig figs while driving, with a digital one, you know if you're at 20 or 23 (after your car speedo error, obviously). The implication is that it previously wasn't so important to drivers.
throwaway0a5e 5y ago
Or the overtaking truck could just go faster to match the speed of the lane it's getting into. It doesn't matter what you're driving, if you're getting into a flow that's going faster than you are you are either going to force it to slow down or cause a crash, depending on how much space is in front of whoever you choose to cut off. I'll generally cut the trucks some slack because it's not like they can gain 10-15mph at the drop of a hat but when car drivers do it it's impolite and amounts to a big middle finger to everyone else.
- deleted 5y ago
  [deleted]
- frosted-flakes 5y ago
  Commercial trucks usually have speed limiters.
  - philote 5y ago
    I guess it depends on the country. Here in the US trucks don't have limiters.
    - frosted-flakes 5y ago
      They do if they want to cross the border into Ontario or Quebec.
    - sokoloff 5y ago
      In the US, speed limiters have been required on heavy-duty trucks since model years in the early 90s (1992 I think). They are not required to be set to a speed matching the prevailing highway speed limit, but the overwhelming majority of fleet has them.
- dtgriscom 5y ago
  The parent comment suggested that both trucks were going as fast as their engine control would allow.
- deleted 5y ago
Gare 5y ago
It's actually 52 m. The cab of the overtaking truck has to clear both the truck it's overaking and place itself one full length ahead.
- notreallyserio 5y ago
  I can't remember the last time I saw a truck have at least one full length of space in front of them, except when there's basically no traffic at all. They're usually one to one and a half car lengths apart.
rootusrootus 5y ago
> probably because they're both on their limiters I suspect this happens less often than people think. Most elephant races are up hills and are at speeds significantly under the demonstrated maximum of the truck on level ground. I routinely get passed by tractor/trailers when I'm doing 65mph in the right lane of the freeway with my travel trailer. Even a slight incline and I end up blowing right past them. My guess is that two fully loaded trucks just have a similar maximum speed in a given power-limited situation, and when combined with the natural desire to not give up even 1 mph of hard-won kinetic energy, we end up with elephant races.
- kkarpkkarp 5y ago
  > I suspect this happens less often than people think. depends what you think is "less often than people think", plus you need to put it in country context. In Poland it is a real problem. On the distance o 100 km (60 miles) it can happen 3-4 times. If you travel for 300 km it means you will be swearing 10 times when stuck in a line after some lorry.
  - rfrey 5y ago
    My read of your parent's comment was that elephant racing due to speed limiters happens less often than people think... Not the races themselves.
    - 4O4 5y ago
      Depends on the country I guess. In Poland there is really no other reason than slight differences between speed limtliters callibration (+-2kph). No uphills on Polish highways, no other variables, just that one. 2 minutes of trucks overtaking each other on 2-lane is still very common view even though there are more and more places when overtaking is explicitly prohibited for trucks only to prevent these situations from happening in critical areas. Also the speed difference is much higher on Polish highways because cars can legally go as fast as 140kph while upper limit for trucks is 90kph. This is a huge difference, lots of brakes to burn before you slow down to match that speed.
mgarciaisaia 5y ago
I totally agree with the elephant racing. If we saw traffic as team-play, things would be much easier. A similar case, more frequent case here in a touristic place with single-lane routes is lines of vehicles right after each other, that don't know how to overtake the one before, but neither leave space in between so someone else _can_ overtake them. In a complicated mountain road, I _may_ be able to overtake a truck once in a while (depending on incoming traffic, turns, and going uphill/downhill) - but the effort required to overtake 2, 3 or more vehicles at a time is almost impossible.
hoseja 5y ago
Aren't these elephant races deliberate traffic shaping by the truckers? I think I heard that somewhere.

vladvasiliu 5y ago

While I agree with your overall point, I think there's even lower hanging fruit that's still not picked up. In France, at least, when there are more than two lanes, basically no one drives on the rightmost lane. Yes, I know about the traffic law requiring staying in your lane if there is dense traffic. I'm specifically talking about the case when there is little to no traffic.

adhesive_wombat 5y ago
That's a huge issue too in the UK, especially on three lane roads and wider, where you can just sit in lane two forever, if your skin is thick enough, and everyone will just have to over- and under-take you. It's actually been illegal for some years and can get you a £100 fine, though I don't know if that's ever actually happened: you'd have to have the bad luck to encounter traffic police who do anything other than speed-gun free-flowing motorways from bridges.

ErikVandeWater 5y ago

Elephant racing could have the unintended benefit of reducing accidents (and their severity) by slightly lowering the overall speed of traffic. If elephant racing very occasionally prevents an accident due to slower speeds, it might benefit all road users as they don't have to pull over for emergency vehicles, and don't have to wait for debris to clear.

FabHK 5y ago
Unlikely. I think 10%+ changes in speed are much more dangerous than a 1% higher speed overall.
sojournerc 5y ago
What I see is definitely more dangerous. Cars stack up in the passing lane behind the passing truck. Impatient people then jump into the empty slow lane to pass the line of cars on the right, then merge greedily cutting in front of the line, making the whole situation worse.
- midasuni 5y ago
  So drop the limit to 60 for everyone?
  - emteycz 5y ago
    Low limit for everyone leads to more accidents - drivers watch speed and try to race between speedcameras instead of riding through quickly but safely.
    - adhesive_wombat 5y ago
      Right: even with current limits, I spend a completely unreasonable amount of time glancing at the speedo, worrying about if I'm going over the limit and trying to shepherd the speed within the limit, rather than paying more attention to the traffic conditions around me. This is actually much worse on 20 roads that are converted from 30s by just swapping the signs: they were specifically designed for higher speed, so it's a constant, conscious effort to keep the speedo in mind and sight and carefully not drive to the road. I feel that this is something people didn't have to do so much: with an analogue speedo, you can't really see your speed to 2 sig figs while driving, with a digital one, you know if you're at 20 or 23 (after your car speedo error, obviously). The implication is that it previously wasn't so important to drivers.

throwaway0a5e 5y ago

Or the overtaking truck could just go faster to match the speed of the lane it's getting into. It doesn't matter what you're driving, if you're getting into a flow that's going faster than you are you are either going to force it to slow down or cause a crash, depending on how much space is in front of whoever you choose to cut off. I'll generally cut the trucks some slack because it's not like they can gain 10-15mph at the drop of a hat but when car drivers do it it's impolite and amounts to a big middle finger to everyone else.

deleted 5y ago
[deleted]
frosted-flakes 5y ago
Commercial trucks usually have speed limiters.
- philote 5y ago
  I guess it depends on the country. Here in the US trucks don't have limiters.
  - frosted-flakes 5y ago
    They do if they want to cross the border into Ontario or Quebec.
  - sokoloff 5y ago
    In the US, speed limiters have been required on heavy-duty trucks since model years in the early 90s (1992 I think). They are not required to be set to a speed matching the prevailing highway speed limit, but the overwhelming majority of fleet has them.
dtgriscom 5y ago
The parent comment suggested that both trucks were going as fast as their engine control would allow.
deleted 5y ago

Gare 5y ago

It's actually 52 m. The cab of the overtaking truck has to clear both the truck it's overaking and place itself one full length ahead.

notreallyserio 5y ago
I can't remember the last time I saw a truck have at least one full length of space in front of them, except when there's basically no traffic at all. They're usually one to one and a half car lengths apart.

rootusrootus 5y ago

> probably because they're both on their limiters I suspect this happens less often than people think. Most elephant races are up hills and are at speeds significantly under the demonstrated maximum of the truck on level ground. I routinely get passed by tractor/trailers when I'm doing 65mph in the right lane of the freeway with my travel trailer. Even a slight incline and I end up blowing right past them. My guess is that two fully loaded trucks just have a similar maximum speed in a given power-limited situation, and when combined with the natural desire to not give up even 1 mph of hard-won kinetic energy, we end up with elephant races.

kkarpkkarp 5y ago
> I suspect this happens less often than people think. depends what you think is "less often than people think", plus you need to put it in country context. In Poland it is a real problem. On the distance o 100 km (60 miles) it can happen 3-4 times. If you travel for 300 km it means you will be swearing 10 times when stuck in a line after some lorry.
- rfrey 5y ago
  My read of your parent's comment was that elephant racing due to speed limiters happens less often than people think... Not the races themselves.
  - 4O4 5y ago
    Depends on the country I guess. In Poland there is really no other reason than slight differences between speed limtliters callibration (+-2kph). No uphills on Polish highways, no other variables, just that one. 2 minutes of trucks overtaking each other on 2-lane is still very common view even though there are more and more places when overtaking is explicitly prohibited for trucks only to prevent these situations from happening in critical areas. Also the speed difference is much higher on Polish highways because cars can legally go as fast as 140kph while upper limit for trucks is 90kph. This is a huge difference, lots of brakes to burn before you slow down to match that speed.

mgarciaisaia 5y ago

I totally agree with the elephant racing. If we saw traffic as team-play, things would be much easier. A similar case, more frequent case here in a touristic place with single-lane routes is lines of vehicles right after each other, that don't know how to overtake the one before, but neither leave space in between so someone else _can_ overtake them. In a complicated mountain road, I _may_ be able to overtake a truck once in a while (depending on incoming traffic, turns, and going uphill/downhill) - but the effort required to overtake 2, 3 or more vehicles at a time is almost impossible.

hoseja 5y ago

Aren't these elephant races deliberate traffic shaping by the truckers? I think I heard that somewhere.