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The waiting time paradox: why is my bus always late? (2018)

(jakevdp.github.io)
219 points skadamat | 9 comments | 20 Aug 24 13:55 UTC | HN request time: 0s | source | bottom
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rjmunro ◴[20 Aug 24 17:11 UTC] No.41301868[source]▶
There's another thing that happens with busses that makes it worse.

The further behind the previous bus a bus is, the more people will arrive at the bus stop. The more people there are at the stop, the longer the bus has to spend picking them all up and selling them tickets etc. Therefore the delayed bus will tend to experience more delay. The bus behind them will have less people to pick up, so it will spend a shorter time at stops and tend to catch up with the first bus, so the two busses are dragged towards each other.

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mitthrowaway2 ◴[20 Aug 24 18:05 UTC] No.41302390[source]▶
That bus with more riders on board also has a higher probability of needing to stop to let people off at each location as well, slowing it down even further!
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ajuc ◴[20 Aug 24 18:45 UTC] No.41302756[source]▶
This is part of a good route design - most bus stops should be "mandatory" - which means the bus stops there no matter what. Some bus stops are "optional" - driver only stops there if there's somebody waiting or if somebody in the bus presses the "STOP" button near the doors. It's marked on the timetable which bus stop is optional.

It's not worth it to make every stop optional because then the routes become too unpredictable and scheduling is hard. Usually there's like 5-10% of optional bus stops on each route - only in the places where very few people get in/out.

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1. mitthrowaway2 ◴[20 Aug 24 18:57 UTC] No.41302869[source]▶
For express or intercity busses, that makes sense, but for high-frequency regular bus routes, I can't imagine that working. It means thar bus stops would have to be extremely sparse, or else the bus trips would need to be extremely slow.
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2. ajuc ◴[20 Aug 24 19:06 UTC] No.41302955[source]▶
Exactly the opposite. It sucks for intercity buses, cause there's no point. Bus stops are rare and buses don't "bunch up". It's essential for city buses.

This is how it works in every big city in Poland, it's working great. More cities started to use this system over time, because it improves the scheduling so much.

The point of city buses is that they drive in traffic anyway - they rarely drive over 50 km/h and they stop every 5 minutes. How regular they are is MUCH more important than how fast they drive.

If you skip 3 stops because nobody waited there - you get to the 4th bus stop 5 minutes too early and wait for 5 minutes there - potentially blocking the bus stop for others and wrecking havoc with the scheduling. Much better to split these 5 minutes between the bus stops where nobody is blocked.

It's like in gamedev - you don't want to optimize happy case cause you're making the situation WORSE. If your fastest frame takes 5 ms instead of 10 ms it changes nothing at best (and makes for more jerky movement at worst). If your longest frame takes 15 ms instead of 18 ms - it means you can keep consistent 60 FPS now - and that's a HUGE win.

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3. SoftTalker ◴[20 Aug 24 19:15 UTC] No.41303039[source]▶
City buses stop much more often than every 5 minutes in my experience. It's more like every couple of blocks, sometimes every block, at least in the densely populated areas.
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4. mitthrowaway2 ◴[20 Aug 24 19:47 UTC] No.41303351[source]▶
For intercity busses, keeping an accurate schedule is essential. If you miss your bus because it ran ahead of schedule, it's not a five-minute wait for the next one; you'll possibly even be booking a hotel for the night.

For express busses, stops are far enough in between and all major locations, so you may as well stop at all of them.

For milkrun busses, where the frequency is so high, scheduling errors are only really a problem if the busses bunch up and create excessive gaps.

If a bus trip takes 45 minutes when a car takes 15, more people drive and then traffic gets bad. But busses with dedicated lanes and coordinated light-timing can go much faster than traffic, when they aren't stopping for passengers!

I think you and I must live in cities with very differently-run transit companies!

5. supertrope ◴[20 Aug 24 20:37 UTC] No.41303809[source]▶
>bus stops would have to be extremely sparse, or else the bus trips would need to be extremely slow.

Way too many transit operators choose extremely slow. Having bus stops every 100m is popular because it offers almost door to door service. But when every single person separately boards it results in the vehicle being stopped 1/3 of its running time! People generally prefer faster bus routes (average 20 MPH) even if it requires them to walk a block to the stop versus a service that stops every block but averages 6 MPH (bicycle speed).

https://humantransit.org/2011/04/basics-walking-distance-to-...

6. emmelaich ◴[21 Aug 24 00:52 UTC] No.41305669[source]▶
Same in Sydney Australia,

> If a bus is indicating ( min 5 secs ) and is pulling out from a bus stop they have right of way. Failure to Give Way is worth a $362 fine and [demerit] 3 points.

7. bluGill ◴[21 Aug 24 01:25 UTC] No.41305866{3}[source]▶
That is way too often, it makes service too slow. People have things todo and sitting on the bus is not one oi them (even if they are doing something it is rarely what they want todo.

what is right is a compromise but everx block is too much

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8. mitthrowaway2 ◴[21 Aug 24 02:34 UTC] No.41306250{4}[source]▶
I agree, but a five minute drive is about a 30 minute walk (for an able-bodied person), which is way too far between bus stops for a non-express bus. Especially if you have to catch a connecting bus going along one of the major streets your bus skipped by.
9. ajuc ◴[21 Aug 24 09:59 UTC] No.41308594{3}[source]▶
Yeah, I checked the routes I take and it's 40 minutes for 25 bus stops so about 1.5 minutes between stops.