Hacker News Reader

Comment by adrianmonk | Hacker News Reader

Would it help to have the trailing bus pass the leading bus when they bunch up?

My reasoning:

(1) As the article said, full buses move slower because more passengers means more boarding/unboarding time at stops.

(2) The lead bus is the fuller, slower one. Slower bus in front means buses get closer together.

(3) If one bus passes the other, then you have the faster bus in front and the slower one behind. They should then get further apart.

At least they should for a time. The now-leading bus is going to scoop up a lot of passengers at the next several stops and the now-trailing bus won't, so the leading bus will eventually slow down. So it's not perfectly self-balancing or anything, but maybe it would get some distance between them. More distance than not doing it.

View on HN

When busses get bunched here, the lead bus just tends to skip stops and leave them for the trailing bus. This doesn't really seem to help much. They usually both stay pretty close together and, as a passenger, you end up standing there confused as to whether the bus just left you or not if you can't see the one behind.

The lead bus is much less equipped to skip a stop if it has more passengers, because there's a greater chance of a passenger needing to stop to disembark. In Chicago, you will see a trailing bus skip but it can do so because the driver hasn't gotten and cord-pulls to signal someone getting off.

That depends on how many/how frequent your stops are. Here in the north of the UK, a 30 minute journey on an urban bus could pass 60-80 stops, many of which will see no-one wanting to get on/off

The one that came to mind as I wrote that was the one I take after work. Most people tend to get off at the train station at the last stop so the bus only really stops for pickups, other than occasionally. The bus goes through an area mostly full of offices and industrial type buildings until it reaches the train station. There's not much inbetween but the same thing tends to happen. Even on other routes here though, busses tend to do the same thing when they're bunched.

A few more points regarding (1). The longer a bus takes to arrive, the more people will accumulate at the next stop, thus compounding the problem. Also, all people don't board the bus at the same speed. The more people that accumulate, the higher likelihood you have of getting an outlier when it comes to boarding time (wheelchair, elderly, bikes, etc). So the later a bus runs, the later it's likely to be.

You are forgetting people who would want to get off that stop, so this is may not be an option.

The lead bus can slow down between stops and let the empty bus overtake. Essentially "stop" several bus-lengths before the next stop and let the empty bus overtake and pull into the stop ahead of it.

The full bus pulls in directly behind the lead bus and lets passengers out.

The bus in front will have more people, and more likely to stop to let people off (and on).

Meanwhile, the one following behind will be emptier, and thus less likely to need to stop, meaning it can easily pass the one in front (while that one is at a stop for entering/exiting passengers) and then itself take on more passengers at the stops ahead --- which then gradually slows it down too, but at the same time the one behind will be mostly emptying.

I'd say it is reasonably self-balancing.

Wouldn't that mean when the bus overtakes it's now taking more passengers and therefore slowing down. The bus it just overtook (which would have quite a few passengers) is now speeding up (but also having to drop off passengers, possibly even stopping at the same stops the previous bus just stopped at.

So it just adds more bunching, doesn't fix anything.

If the bus that overtakes doesn't stop at the next stop but overtakes several stops (or until a passenger needs to get off but should be rare as emptier then the bus it overtook). And then start from there.

Someone mentioned this solution but called it random teleport.

That bus stop but in front of the slow bus.

They do that in NY. It typically equalizes and returns to bunching within a few stops, especially on busy routes.

What I see sometimes is that the delayed, leading terminates early and turns around. The later bus then picks up the passengers. Slightly uncomfortable for those passengers, but brings the bus back into schedule (including the driver who has limited working time and a replacement driver expecting the bus somewhere)

This would help with not wasting the trailing bus's extra speed, but I think the buses being that close together is already considered failure. And in the real world, there would be many more stops on a circuit. Any advantage the faster bus has will be reset in 1 or 2 stops, and on a route with 10-20 stops, the extra space between them is negligible.

You could probably have a computer calculate which stop the trailing bus should jump ahead to.

Then you have the trailing bus switch to "out of service" mode (so it doesn't enrage people when it passes a bunch of stops) and skip ahead 4 or 5 stops or whatever the computer decides is optimal.

Both buses probably need to drop off passengers, though (who would likely be a lot more enraged than people who don't get picked up by the first bus if they didn't get out where they wanted).

Anyway, I think the leading bus skips stops when possible, at least here. I don't think people mind that too much, because for all they know, the bus might simply be too full, although that certainly only happens on exceptional circumstances if ever around here.

The London Underground sometimes skips stops in order to uncongest lines after a temporary delay. They tell everyone on the trains that will be skipping stops that it's happening, and anyone who wants the intermediate stops has to get off and catch the next one.

This probably wouldn't work for buses that take a lot longer to load/unload though...

This is amazing! I wish the DC Metro did this.

When I lived in the DC area, the Metro would indeed skip stops after delays sometimes.

Here's an article talking about it: https://ggwash.org/view/38198/expressing-trains-helps-metro-...

The NY subway will also sometimes have trains switch from local to express or vice versa to help recover during delays.

It would be horrible if the slow bus behind was actually too full to pick up people so you have an empty bus passing stops that the trailing bus will also skip!

Welcome to Baltimore.

This may not work as well as you'd like if passengers need to get off frequently.

They will sometimes do that in Vancouver (or at least they did when I lived there). The lead bus will skip stops if it's able (no one getting off) leaving the passengers for the following bus, but if it has to stop, the trailing bus will just go ahead if it has no one getting off at that stop.

EDIT: it doesn't really help with the bunching, but it does help load balance between the two buses. I've been on rides where two buses passed each other several times.

The bus driver of the 'skipping bus' also has to be reasonably confident that the next bus will show up shortly. Otherwise, as a passenger, it's very frustrating to see one zoom by: but if you can see another one down the road, then you won't be freak out.

They all don't go to the same destination. They have an overlap of route but all of them go to different destinations. So you cannot just skip a bus stop. You are very rarely if ever going to see the same numbered buses bunched together

Don't overgeneralize. The featured article (simulation, really) is about bunching of buses on the same route, a phenomenon that I, a daily bus commuter in Los Angeles, USA, routinely witness.

Stops on the routes I take are also generally skipped unless someone is waiting at them or a passenger has pulled the cord/pressed the button to request a stop.

I am not overgeneralizing. I am mentioning every use case!

The stops are skipped because no one wants to get out of the bus and there is no one to board it. It has nothing to do with bus bunching.

Here in downtown Vancouver, there are some stops that have 5 different numbered buses making stop. Can they just skip ahead because there are a couple of buses already there at the stop?

To really make this works will have to check 1. Is the bus stopped in front of me the same numbered bus? 2. Does it have enough seats to board people that have lined up?

If yes then lets just not stop.

My first thought is that this would break a shitload of software around bus time indicators - i.e. on bus stops and presumably whatever API the website talks to. I believe the buses function like trains in that sense - they're numbered not just by route, but by actual bus.

Would be nice though.

The 'next bus' signs around here are all based on realtime GPS-tracking from the buses ('free wifi' is often piggy backed on the data connection the bus thus has to maintain.

I've seen buses run so late that they bunch-up and even to the point where they asked us to switch to the front bus so the rear bus could be taken out of service, once, and never seen the displays at the stops get too confused.

Of course trolley buses (or streetcars/trams) can't do this

Trolley buses usually can to an extent - the trolley arm can usually handle the 3m swing or so it takes to pass another bus.

...and then it crashes into the trolley arm of the bus ahead.

New trolley buses often have batteries, so they can run unplugged for some distance.

reattaching the trolley arms without stopping is not so easy

They do that here in Seattle sometimes.

Reply on news.ycombinator.com