Tom Anderson wrote:
On Sat, 14 May 2005, Dave Arquati wrote:


Tom Anderson wrote:

On Thu, 12 May 2005, Dave Arquati wrote:


A very impressive system would be to not only have accurate Countdown
information online and at stops, but also to have
dynamically-estimated journey times to destinations from that stop,
available both online and via Countdown at the stop itself.

Yes, this would be very cool, but the amount of effort it would
require to gather the traffic data, process it to produce congestion
forecasts (not entirely unlike weather forecasting - congestion is a
dynamic, nonlinear, mobile phenomenon), work out delays to services
and distribute this to every bus-stop would be substantial.

I don't (think I) mean forecasting congestion, as such... just using
data on current traffic speeds to estimate those journey times.


Ah, but that does involve forecasting - if you want to know about delays
that a 38 at Victoria might suffer when it gets to Hackney, you need to
have some idea of what the traffic is going to be like about 45 minutes
into the future.

I don't think that's entirely necessary (although it would certainly be
impressive!). Knowing about existing delays on the route will give
vastly superior realtime information to that currently available - so if
congestion is already occurring in Hackney, it would be highlighted at
the 38 stop at Victoria, on the assumption that congestion tends to
clear slowly.

If, say, congestion then arises in Hackney whilst the 38 is en route at
TCR, then an on-board information system (probably using the new video
screens appearing in buses) can dispense this information to the
passengers, who can then make their own minds up about any route
changes. Messages could also be sent out to people who have signed up to
have their routes to/from work tracked for disruptions - this is already
done for Tube lines via email or SMS, and I imagine it could be easily
extended to bus routes.

On the flip side, it's quite likely TfL are already doing this forecasting
as part of their realtime congestion management work.

I wonder how they would do it. Weather forecasting involves predicting
movements of fronts and such (although I know very little about it!),
but congestion forecasting would seem more difficult as it can arise
much more spontaneously - e.g. if a lorry breaks down in an awkward
location.

Maybe I should make this my Masters project next year... I know a couple
of friendly computing/information systems students who might like to
collaborate!

The data collectors are already out there in the form of on-bus AVL,
C-charge cameras, TfL traffic cameras, RAC info etc.


Is that network dense enough? The CC cameras are only in a ring round the
zone (and possibly inside it - but not much outside it) and TfL and RAC
cameras are only on major arterial routes. The AVL data, though, would
cover all the roads you needed to know about - pretty much by definition!

I heard somewhere that TfL already track vehicle speeds through the
C-charge area by using the cameras, although I don't know quite what
they track. AVL data seems like the most obvious choice, but is somewhat
restricted on roads used by few or infrequent buses, as one bus behaving
erratically could seriously skew the data. Speeds of all vehicles would
be more useful - that can be obtained either via digital speed cameras
(which could presumably be set to log all vehicle speeds) or via those
tubes you sometimes see across the road, which are used to check traffic
speeds (although they are far from infallible).

(snip)


--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London