I'd like to tell you a bit about my
latest obsession which is the early days
of the railway; things were very exciting.
So you have to imagine this is like
completely brand new. They had no idea of
the best way to send trains around the
country. At this point in time stage
coaches had been the normal form of
transport, and with stage coaches they
had timetables - but I mean they were
loose at best. So posters would appear
saying what time a stagecoach would
leave and it would often
appear with a caveat like 'God willing';
and
'leaving at 12PM, barring accidents'.
I'm not actually joking, those
from genuine posters by the way.
So when it first came to trains they
kind of had the same attitude; just, you
know, chuck a train along the track and
it'll be absolutely fine. Timetables- I
mean these are considered quite loose
guides.
So there was one guy particularly famous,
he was known as the railway king, he was
called George Hudson. He
was once shown that actually his
trains would often run really late, and
so he countered by saying that actually
often they also ran early, so that on
average his trains ran on time.
That's the kind of world we're in. If a
train didn't turn up at the next station
they would often send a train out along
the same track in the opposite direction
to look for it. I don't know about you
but I can definitely see a problem with
that. And actually Brunel in particular
had a very lax attitude towards safety.
So he was once asked what he would do if
he saw another train coming towards him
and he responded that he would basically
stoke the fires, go full speed and just
try and ram them off the tracks. Just a
little bit of background for you from
the type of situation we're in.
But then there were some really quite
major accidents; once passengers started
going along the railway rather than just
freight there were some quite major
accidents.
And
people realised that it was really
important to work out
a way to make sure that there was only
one train on a piece of track at a time.
I'm going to struggle to continue my
excitement of this because I think it's
genuinely amazing, but this really
incredible idea was had by a French
railway worker called Charles Ibry, this
is 1847. And he decided that maybe what
we should do is use a very particular
type of graph - I'm calling it a train
graph, I'm not sure if that's the
official phrase,
but here is how the train graph works. So
his graph manages to simultaneously show
all of the stations between Paris
and Rouen.
So you have all of these stations along
here - I'm not even going to pretend that
I know what they are -
do you want to give me some comedically
French names? - (Brady: Renault, Eiffel Tower)
Yeah, okay okay.
You got the Eiffel Tower,
you got Renault up here; Poincare I'm
pretty sure.
(Alain Prost?)
(Zinedine Zidane?)
Look this is accurate - you've got
Oh la la, there we go, and baguette.
This is getting increasingly problematic
as we go along. So you've got all of your
stations, the important thing about this
is the distance between the stations on
here represents the distance along the
track, you're representing the real
railway track on the paper. But the other
dimension of course is time, and then
along here - let's say your trains start
at like 6AM and then let's go through
to like midnight. So you've got a
one-dimensional map on one side and then
you've got the time of day along the
other. Now you can start adding trains on
this. So let's say that you have got a
train that leaves Paris at 6AM and gets
to Rouen at - I'm just gonna assume this
is quite a slow train, given the way that
I've drawn this
graph, just go with me. Okay so you've got
a train that leaves Paris at 6AM and
let's say that it gets in to Rouen at
let's say 3PM. So now all you have to do
is draw a straight line between the two,
right, that's kind of straightforward and
nice and easy. Let's imagine then that
you have a train that you want to leave
Poincare and it leaves Poincare at 6AM
and it gets in let's say at 5PM. Now
that looks like it would be fine, you
could just draw that line on the track;
except
you would have a massive problem if you
did that because where these lines cross
on this graph,
it also means that they cross in real
life. It means that there is going to be
a point at about 3 o'clock in the
afternoon
where these two trains are going to have
to cross over on the same piece of track.
(So basically that that Paris train is)
(going to kind of go up the back side of)
(that one isn't it?) - Exactly. You're
going to have a giant problem, you've got
a really slow freight train and then
another fast one that wants to come
through. I mean you just can't do it. So
if you want- if this train can't go
can't go any faster the only option that
you have is either to move this speed
train and change the time of that, or
instead to just slide this train along,
and have it so that it actually leaves
Poincare just after this express
train has come through. So have it so it
does something like this. So now actually
that's fine, that train fits all nicely
there's no problem there at all. Or the
other option is that you could change
the speed of this train so that you can
still have it leave at 6AM but
actually try and give it some gusto and
just make it go a little bit faster so
that maybe it arrives at 1PM. So still
not quite as fast as the express train
but just going a little bit faster, those
are your options.
A little bit later you could say, at
this station here, at Alain Prost,
at Alain Prost you could have a sort of
vertical line so that at every point
during the day there was a place at
which a train could pull over and allow
another train to pass, so that any
crossings along that line of Alain Prost
are actually actually fine it's not a
problem at all. In fact let's do that,
let's let's draw a line. So anything
along this red line of Alain Prost is
absolutely fine. So anything that crosses
there isn't going to be a problem. But
you start populating this graph with all
of these trains, anything that needs to
go from one place to another. This
essentially allows you to fix how fast
trains can possibly be; because you know
absolutely cold hard fact you cannot
have two lines crossing on this graph
unless they're at a special station where
you know there's a place to pull over. So
if you've got this really kind of well
populated graph, remember they're always
going in this direction because time
always moves forwards, and in this
particular example they're always going
from Paris to Rouen rather than the other
way around on the line that we have. But
this is like a way that you completely
have your constraints totally fixed. Now
the thing about this graph that I think
is so amazing; invented in the 1840s,
still used today. So until very very
recently if you went into somewhere like
National Rail you would find people
with- with literally like this, pieces
of paper and rulers working out exactly
how fast the train is; faster trains
being slightly steeper, slower trains
being a slightly shallower gradient, and
they would literally be with a pencil
and paper trying to work out how to
timetable new trains. And all of the
software now that has replaced the paper
still operates on exactly this principle,
that the best possible way to create a
timetable for real life is to kind of
visualise it in this imaginary space of
distance and time.
In Singapore on the MRT, the metro
stations there, there was an issue a
couple of years ago with a rogue train.
So there was this this problem on the
track where lots of trains were losing
power, they weren't really sure what was
going on; and it wasn't one train that
seemed to have an issue, it wasn't like
they could narrow it down and say, okay
this is the train that's that's the
problem. It was lots and lots of
different trains were having issues. And
they worked out what the problem was
only by using one of these train graphs
because
when they plotted the entire day's
timetable on the train graph they could
see that actually one naughty train was
essentially emitting a signal and
causing knock-on effects in any train
that passed it. So it would be as though
this train as it kind of goes along ends
up causing a problem in this train and
in this train and in this train; anytime
it got within the vicinity of another
train,
this naughty train, the rogue train
was causing an issue. And it's only by
visualising it using these graphs that
they spotted that was the problem.
Check out the links in the video
description for more of our videos with
Hannah; we'll also have links down there
to the latest of Hannah's books,
podcast work, anything else that might be
of interest: go and check out the video
description. - I always thought that those
were the couples who who would end up
being the most successful, but the team
found that it's actually the exact
opposite that's true.