
Mathematical model suggests London Underground may be 'too fast' - uxhacker
http://www.bbc.com/news/science-environment-34334794
======
snowwolf
The ideas and models are interesting from a systems thinking perspective and
it is certainly true that local optimisations can have unintended systems
consequences, but unfortunately it doesn't model reality when it comes to
London.

The paper makes the flawed assumption that people commuting into London from
outside the boundaries of the Underground network start their journey by
driving to the boundary and entering the system at that point, which as anyone
in London can tell you is not the case. Most commuters from outside the
network will arrive at one of the main overland train terminals (Euston,
Paddington, Waterloo, Victoria, Kings Cross, etc.) and change mode of
transport at those points. Those points certainly do see large congestion, but
they are a very different beast to road traffic so I very much doubt the same
conclusion would be reached if they were included in the model. The paper also
ignores the bus network, which is also heavily used in London, which is I
think also different to say New York.

If you are going to start studying systems then you need to look at the whole
system otherwise you are still just doing 'local' optimisations. If their
conclusion/recommendation were to be implemented, I suspect it would make
things worse overall as they haven't understood the system.

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gearhart
This article suffers from serious Chinese whispers.

The clickbait title doesn't reflect the conclusions of the article, which
don't reflect the conclusions of the paper, which don't reflect the actual
evidence given by the simplistic experiment that the physicist responsible for
it decided to use to model the real-world system.

The guy who wrote the paper was doing some sensible academic research that
really should have had no conclusions - it just worked towards a new facet
that should be used when modelling transport systems in cities, which is
perfectly commendable and useful, but can't be relied on as a standalone
system (in the same way that you couldn't model all of the interactions in the
universe using only magnetism). Deciding to draw the conclusion that he could
predict an optimal speed for the underground to move at was foolish and
detracts from the original paper (although I'm sure it garnered it much more
attention).

That the guy is quoted at the end of the article admitting that his
conclusions are evidently nonsense and that they should probably throw in some
"secondary terms to account for complications he just thought of" is almost
too perfect.

[https://xkcd.com/793/](https://xkcd.com/793/)

~~~
jandrese
I have to admit I was wondering if at some point the author was modeling
passengers as perfectly spherical objects vibrating in a sinusoidal fashion.

It reminded me of all of those traffic studies where they conclude that they
can increase traffic flow through a city by reducing all of the speed limits
and taking away lanes and then something magical happens. Or the counter
studies that say adding lanes reduces the total volume of traffic a road can
process because it will make more people take the road and cause it to back
up.

------
vidarh
> "We create these connections, and then we make an assumption, which is: When
> someone wants to go from A to B, they look for the quickest path - whatever
> the mode."

That sounds like a crazy assumption for commuting.

This may be true for some subset of commuters, but when commuting via public
transport regularly, a lot of people quickly develop favoured routes that
often have nothing to do with speed, and everything to do with flow and
convenience and what trains you can get seats on, and what lets you actually
spend your time reading rather than changing trains.

Over 15 years of commuting in London, the quickest path has almost never been
the route I ended up favouring.

~~~
odonnellryan
It's true. How much time is non-stop worth? Or a seat the whole ride? It is
worth something!

~~~
vidarh
I've been willing to about doubling my commute to be able to just sit down on
a bus or train the whole way. I treated it as a time saving: Yes, I spent more
time commuting, but that time was spent napping or reading, so it was a net
gain for me in _usable_ time.

It's also a cost issue for many. An annual Zone 1-2 Travelcard costs GBP
1280,-. A Zone 1-9 Travelcard costs GBP 3336,-. The cheapest single zone
annual cards cost 964,-. While a Bus and Tram pass costs 840,-.

Depending on where and how often you need to travel, for many it's worth it to
pay the time penalty of taking the bus rather than paying for one or more
extra zones, or paying for tube/train at all.

It's not _that_ uncommon for people to do 1-1.5 hour bus commutes that'd have
been far shorter, and more expensive, by tube/train.

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celticninja
This analysis ignores people who use only the train and tube or just the tube.
If you hinder the tube to try and improve traffic what will happen is traffic
will eventually increase where you have made improvements (the bottlenecks
referred to in the article) and the tube service has still been degraded.

The failure of the analysis is to assume that car drivers should be a
consideration (perhaps that is due to the US bias toward car travel over
public transport). Really we need to be improving public transport such as the
tube so much that car driving is disincentivising as much as possible and
public transport is incentivised as much as possible.

~~~
raverbashing
I think you're right on your first paragraph

But the consideration about traffic is not only about cars but people that do
Bus->Tube and vice-versa

~~~
notahacker
I can't see any part of the study that distinguishes between the congestion
effects caused by cars and buses (or indeed walking and cycling, which the
naive speed-optimisation specification of the study assumes away altogether)

This is pretty critical to some of the conclusions: a subway line creates
congestion at the ends of subway lines rather than them becoming a logical
nexus for bus routes.

------
goodcanadian
This is an interesting study, but the "conclusion" is a bit odd. To me, if an
efficient railroad system is causing congestion near the "park and ride" or
equivalent, the answer is to expand the rail network further not to
artificially handicap it.

------
buffoon
The problem is that models rarely replicate reality for very long. I live in a
particularly troublesome bit of London and they used some mathematical
analysis to optimise traffic light timings in the area and celebrated that it
was as success. That was premature; it's measurably worse within two weeks
after people realised that it was a better route and promptly clogged it up.

~~~
wlesieutre
That's the nature of traffic. You make a highway twice as wide and it's great
for a few years until enough people go "Oh! I can live twice as far away, have
much lower rent, and still keep my commute under 2 hours!"

And then you end up with LA.

~~~
wlesieutre
If anyone's curious to read more about this, Wired has a pretty good piece:
[http://www.wired.com/2014/06/wuwt-traffic-induced-
demand/](http://www.wired.com/2014/06/wuwt-traffic-induced-demand/)

------
kazinator
Slowing down trains to solve a bottleneck downstream is like squeezing the
bump in the carpet to another location in the room.

It doesn't make anyone get anywhere any faster, and hurts the commute times of
the people who are not involved in the bottleneck (because, say, they walk or
bicycle to their destination from the train station, or take some other fast
train).

Transportation is about optimizing the average trip time; concern about
accumulation at transfer points is secondary.

------
sandworm101
This analysis seems based on preventing congestion. But congestion, while
ugly, isn't a bad thing. What matters is total journey time.

Imagine if you replaced all the trains with trek-style teleporters. Rather
than 100 people all getting onto a train and being whisked away, they would
all wait in a line outside these devices. That would be an increase in
congestion, more people standing around waiting rather than moving. But if the
teleporters get them to their destinations faster nobody cares that they had
to wait in line.

It's a matter of perspective. The city/transport planners see people standing
around not moving as a bad thing. But the people don't care. Standing on the
slow train or standing in the line waiting for the fast train is all the same
to them. What works best for the people isn't the an elegant system of slow
trains to ensures nobody ever stops, where nobody ever suffers the evil
congestion. What works best for them is getting to work as fast as possible.
If that means crowds at bottleneck where in-feed is slightly faster then out-
feed so be it. Slowing things down, having more people spend more time
standing in trains rather than on platforms, doesn't help them get to work
faster.

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Reason077
Would it even be _possible_ to slow down the Tube while maintaining capacity?

You would have to either make the trains bigger (not possible on most lines),
or add additional trains - expensive, and potentially a safety issue as you
need to make sure there is always an evacuation route available.

Some lines already operate with more trains in service at a given time than
there are platforms on the line.

This study sounds suspicious to me. I wouldn't be surprised if it were
sponsored by cab companies, bus companies, and bike activists :)

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splike
Does this model assume everyone in London has a car?

~~~
Arnt
No. But it does assume that some people can choose to go part of a trip by car
(their own or another) and the rest on the tube, and that these mixed-mode
trips affect congestion for everyone.

~~~
spacecowboy_lon
But thats only going to happen at the extreme ends of the tube system no one
is going to drive further into London to park and then get the tube

~~~
Arnt
Quoting the article: "key locations outside the city centre, where people
switch transport modes, become bottlenecks" and "the underground network, for
example, tends to decrease congestion centrally but increase it where the
underground lines finish."

~~~
spacecowboy_lon
From experience The bottle necks in the tube are not the extremities like
watford or finchly.

------
Arnt
So if the goal of London Underground were to avoid street congestion, and
changing the way the street and underground networks meet were impossible or
illegal, then lower speed would be appropriate.

That's interesting. In an if-and-if sort of way.

