[Talk-transit] Public Transport routing

Roger Slevin roger at slevin.plus.com
Sat Sep 5 10:12:28 BST 2009


As someone sitting on the periphery of OSM, with a particular interest in
the use of NaPTAN and equivalent data for stop points, perhaps I can give a
slightly different perspective on where I would see the boundary that Peter
Miller refers to.

 

Stops are (reasonably) static features.  Railway and Tram Tracks (and
monorails!) likewise.  And because tracks are essentially static, the scope
for different “routes” to be operated over tracked networks is relatively
limited – and therefore the speed of change of routes on tracked systems is
quite slow.

 

But the reason that journey planning systems have to build data every week
in the UK is that we have a free market for public transport provision, and
there are changes happening continually – changes which can only be
reflected in continually maintained data.  The changes are in timetables and
in routes – new routes, routes ceasing, routes being described differently.
Some “routes” are really a collection of subtly different routes – sometimes
with different numbers (or names), and sometimes not.  My advice to the OSM
community is to focus on the things which you can do well, and can maintain
easily, without trying to replicate data from other fast-moving sources
which it would be difficult to keep up with.

 

One of the problems with Google Transit is that the “stops” displayed on
Google Maps are only refreshed when the tiles are repainted – and that
happens three or four times a year.  For public transport information even
that sort of update frequency is too slow for the stops, let alone for
routes or times (Google does update weekly for routes and times, thank
goodness – so it is only the visualisation of the stops that lags behind).

 

That’s my perspective!  I am sure there are other views!

 

Roger

 

From: talk-transit-bounces at openstreetmap.org
[mailto:talk-transit-bounces at openstreetmap.org] On Behalf Of Peter Miller
Sent: 05 September 2009 09:57
To: Public transport/transit/shared taxi related topics
Subject: Re: [Talk-transit] Public Transport routing

 

 

On 5 Sep 2009, at 07:50, Sarah Hoffmann wrote:





On Fri, Sep 04, 2009 at 07:42:58PM +0100, Péter Connell wrote:



To not use timetables would case various aberrant behaviours like 

routing Yorkshire-Scotland traffic via Settle (side-note: does NRES 

still need to be forced to route this way?)

 

Speed differentials are such that you'd need scheduling information for 

any meaningful set up, e.g. here http://osm.org/go/evjiG2F_- where the 

fastest buses run along the bypass


This problem might be solved by adding approximate travel times to
the routes. While timetables themselves are far to complex to add
to OSM, the time it takes to travel between two stations stays
fairly constant. It might be a nice use for the role in route
relations.

The routing still wouldn't be perfect because change times are
also hard to predict when there is no timetable information.
Nonetheless, it would be immensily helpful to plan travels that
involved multiple modes of transport and multiple operators.
If you ever tried to plan a trip from a small town in France
to a small town in Spain, you will know what I'm talking about.

 

I see huge mission creep[1] here. Wikipedia defines Misson Creep like this:

 

"Mission creep is the expansion of a project or mission beyond its original
goals <http://en.wikipedia.org/wiki/Objective_%28goal%29> , often after
initial successes.[1]
<http://en.wikipedia.org/wiki/Mission_creep#cite_note-0>  The term often
implies a certain disapproval of newly adopted goals by the user of the
term. Mission creep is usually considered undesirable due to the dangerous
path of each success breeding more ambitious attempts, only stopping when a
final, often catastrophic, failure occurs. The term was originally applied
exclusively to military operations
<http://en.wikipedia.org/wiki/Military_operation> , but has recently been
applied to many different fields, mainly the growth of bureaucracies
<http://en.wikipedia.org/wiki/Bureaucracy> .

 

Now of course the whole story of OSM has been one of huge mission creep but
at some point are we not going to need OpenStreetShedules (or whatever it is
called) and should that not be the place to access schedules that link
neatly to OSM and get updated on a very regular basis?

 

Personally I would strongly  advocate adding bus stops etc and public
transport routes to OSM because they are the connectors between the
schedules and the physical infrastructure, but where do we stop? I see a
creepage with people adding just a bit more and just a bit more when I think
we all agree that we can't get all the timetable information into OSM, and
even if we could then is it appropriate given that it changes so often?

 

Clearly there are many people who want access to all the information, so all
we need to do now is agree where we are wanting to get to and how the
project(s) will be organised. Are we wanting to get to:-

 

A) A point where all the world's public transport access points (bus
stops,station etc) are in OSM (but not the routes) and then all the route
and other schedule information is available from some other DB

B) A point where all the world's public transport access points (bus
stops,station etc) and all the routes are in OSM and all the other schedule
information is available from some other DB

C) A point where all the world's transport schedules are in OSM and get
updated on a regular basis by Bots?

 

Personally I think we have already gone past point A and I think that is
good. I am happy with B, but don't think C is right for a couple of reasons.
Firstly it will be a lot of data that most people won't be interested in and
does fit very comfortably in the OSM structure. Secondly there are good
reasons why people might want to use different timetables (future or past
ones) and they will then have to have a different DB. The main adgument for
C) is that OSM is adaptable and has accommodated additional data in the
past, so why do it again?

 

I suggest that we focus for now on getting all the bus stops and public
transport routes from all of the 85 Google Transit feeds that are already
available for reuse[2]  (but only the ones where the licensing in compatible
with OSM)  into OSM and then think about setting up OpenStreetSchedules,
OpenTimetableService, OpenStreetTimetables or whatever to contain all the
details we need? For the time being people can dip into these GTFS data
feeds individually, but in time a single big DB might be useful which can
get to chopped up by country or state as is happening with OSM data.

 

[1] http://en.wikipedia.org/wiki/Mission_creep

[2] http://www.gtfs-data-exchange.com/

 

 

Regards,

 

 

 

Peter






Sarah





 

I think this is something that road routing software has struggled with 

a while so there may be some helpful potential approaches from there. 

Though getting the timetables, however difficult, might still be easier!

 

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