[pgrouting-dev] Support for Time Constraints
Stephen Woodbridge
woodbri at swoodbridge.com
Fri May 27 10:18:59 EDT 2011
Jay,
Trying to narrow down some google searches this looks like it might have
some promising candidates:
http://www.google.com/#q=traffic+data+feed+data+standards+tmc+adms
ADMS - Archived Data Management Systems
TMC - Traffic control centers
This looks like a potential site for getting archived real-time data:
https://pems.eecs.berkeley.edu/?redirect=%2F%3Fdnode%3DState
http://pems.dot.ca.gov/
So from a project point of view, I'm not sure it is a good idea to spend
much time research potential data sources and coding tools to summarize
the data into tables. While this is clearly interesting and might be a
good ideas after GSoC, I think it might be a huge time sync and it would
be better to just make some test networks by hand.
One of the problems you will run into with most if not all of these
sites, is mapping sensors to edges. This might not be hard if the supply
the lat/lon of the sensor, but in may cases I think they just supply a
textual description of the sense and you have to map that to a edge.
-Steve
On 5/26/2011 11:31 PM, Jay Mahadeokar wrote:
> Hi,
>
> We had discussed some possible ways of getting the test time-dependent
> data, but reached no particular solution.
>
> I found this link: http://bhelp.traffic.com/
>
> It a Navteq service and provides live traffic information. You need to
> login, and then you can browse live traffic.
> You can select each road and get following info:
>
> - Jam factor
> - Drive time now
> - delay
> - speed limit
> - average speed
>
> I guess, this is exactly what we need. Even if we can record the
> drive-time now, for each road at intervals of 1 hour each for a
> particular city, we will have significant time dependent data.
>
> I browsed the website but did not find any link where this data is made
> available. Is there any way to record this data? Any starting points?
>
> On Thu, Apr 7, 2011 at 10:05 PM, Jay Mahadeokar
> <jai.mahadeokar at gmail.com <mailto:jai.mahadeokar at gmail.com>> wrote:
>
> Hello all,
>
> Just an update - as Daniel suggested I posted a query about
> time-Dependent data in OSM routing list. It seems they dont have
> such data, but people have posted some things that might be useful
> for us in future. Here is link to the discussion -
> http://lists.openstreetmap.org/pipermail/routing/2011-April/001127.html
> You may want to have a look there.
>
> Sorry for the delayed replies, presently, I am a bit occupied by
> college submissions. I will go through the links and the ideas
> proposed here by Daniel and Steve soon. As already said I guess we
> need to put a lot of thought in designing the data model, that would
> be easy for users to use, robust and flexible for different
> applications, and at the same time efficient in terms of query and
> processing time. I will try and come up with thoughts on that soon.
>
> Regarding Navteq data, the website says that only one data-set will
> be allowed to download. So, I was wondering which data should be
> preferred. Also, there are various data-formats that Navteq provides
> data in. Steve, have you downloaded any data which specifically has
> time-dependent edge weights?
>
> Though we will not want the module to follow Navteq standards, any
> time-dependent data would be very helpful for me, since I also want
> to try out some heuristics on that as part of my thesis. The work
> done by R. Geisberger, P. Sanders and others is experimented on the
> Germany data provided by PTV AG
> http://www.ptvag.com/company/contact/. I have requested them data
> for research purposes. Have you worked with their data by any chance?
>
> Regards,
>
>
> On Tue, Apr 5, 2011 at 8:05 PM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
>
> On 4/5/2011 1:37 AM, Daniel Kastl wrote:
>
> Hi Jay,
>
> As Steve said, Navteq sample data is one possibility ... and
> it's better
> than nothing ;-)
>
> Well, I think we should avoid to support a single data
> provider, because
> who tells that the format they defined several years ago is
> the most
> suitable one. It might work perfectly for Navteq and road
> networks in
> countries they are operating, but this doesn't say there
> won't be a more
> clever way to store such an information.
> I think it will be always necessary to transform data into a
> format
> pgRouting algorithms can handle. So it's OK in my opinion to
> define some
> convenient format if there isn't an existing standard
> already (which
> doesn't exist afaik).
> But Navteq is good data for testing, I agree. For the
> beginning I think
> it might be even too complex model, as Steve mentioned there
> are even
> time dependent turn restrictions.
>
>
> I think that the value in looking at Navteq is not to use it
> all, but that it is a concrete data model that expresses all the
> various routing characteristics that you might run into in other
> data sets. Navteq has been the basis for almost all routing
> solution during the past 10-15 years. There are now others like
> TeleAtlas, and even OSM. So look it over and use as much or as
> little as you need to get started. Designing a data model is
> very complex and you can not do it in the abstract - you need to
> know what you are modeling.
>
> As far as defining an data model that is easy for users to work
> with, keep the tables simple to understand and load with data.
> It is better to have 5 simple to work with tables than 1-2
> complex ones. If you need to transform the data inside then have
> a preparation function that reads the user tables and applies
> them to the graph. So examples of user tables might be:
>
> o bus, train, ferry, airline schedules
> o live traffic data table
> o historical speed estimates by day/time (as Daniel mentions below)
> o transfer rules - required pre-deparature arrival time when
> transferring to a different transportation mode and
> post-scheduled arrival wait time when transferring from a mode.
> EG, must arrive at airport 2 hr before flight departure and
> allow 45 mins after arrival to collect baggage or longer on
> international flights. (this might not apply to your specific
> problem)
>
>
>
> A good place to discuss such a question might be also the
> "OSM routing"
> mailing list. In the worst case nobody will answer. But
> maybe you will
> start a long discussion as there are several people very
> interested in
> routing related topics. OSM data would be nice, if we could
> make use of
> it, but I fear that not many mappers really think about
> time-dependent attributes. Probably in Germany you can find
> such a data.
>
>
> Yes, working with OSM is another good possibility.
>
>
> I thought a bit about some possible cases for time dependent
> road networks:
>
> * In Japan a big issue for navigation software are so
> called "School
> Zones", which are areas around schools obviously,
> which are closed
> for motorized traffic at certain times in the morning.
> * In Europe I know about pedestrian areas for example,
> which can be
> used for delivery of goods after regular business
> hours. Or heavy
> trucks are not allowed to access roads during certain
> times.
> * Some highways/roads in Germany have a speed limit
> during night time
> * Ferry services might only operate during day time (so
> if you
> missed the last ferry, you might have to take a longer
> way)
> * In Japan they have so called VICS data
> (http://www.mlit.go.jp/road/ITS/conf/2006/ts20.pdf)
> collected from
> road sensors, which can tell the typical speed on
> roads during
> certain hours.
>
> ... and so on ...
>
>
> One last thought on loading data. I work a lot with Navteq and
> LOTS of other data sets. The one common theme that I come back
> to is that I create data loaders for the various data sets I
> work with so I can load the data into the database and I always
> end up transforming the data into a simpler model that is easy
> to work with and then used by whatever application I am working
> on. Sometimes I transform the data in the loader and sometimes I
> just load it raw and transform it in the database and then drop
> the raw data tables.
>
> Hope this helps,
> -Steve
>
>
> I think what pgRouting is currently missing are some sort of
> "unit
> tests" on some test network. This can be a regular grid with
> costs
> assigned, that model a certain routing case. It would be really
> convenient to have something like this.
>
> Daniel
>
>
> 2011/4/5 Jay Mahadeokar <jai.mahadeokar at gmail.com
> <mailto:jai.mahadeokar at gmail.com>
> <mailto:jai.mahadeokar at gmail.com
> <mailto:jai.mahadeokar at gmail.com>>>
>
> Hi,
>
> Since we will be working on time-dependent shortest path
> problem, I
> was wondering if time-dependent geographic data is
> freely available
> for research purposes. [1] states that we witness an
> increasing
> number of navigation service providers (such as Navteq and
> TeleAtlas) have started releasing their time-dependent
> travel-time
> datasets for road networks at high-resolution temporal
> granularity
> as fine as one sample for every five minutes.
>
> I guess that data is not freely available. Anyways, if
> you know such
> data-source can you please direct me? Besides this
> project, I am
> also working on some new heuristics for time-dependent
> shortest path
> as part of my thesis and the data would be really
> helpful for my work.
>
> Thanks.
>
> [1] http://portal.acm.org/citation.cfm?id=1869865
>
>
> On Thu, Mar 31, 2011 at 7:49 PM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>
> <mailto:woodbri at swoodbridge.com
> <mailto:woodbri at swoodbridge.com>>> wrote:
>
> On 3/30/2011 9:45 PM, Daniel Kastl wrote:
>
>
> float cost := getEdgeCost(time,
> vehicle_type,
> node_from,
> node_to);
>
> or something like that. Where time
> could be NULL
> for some
> default
> behavior, or a value that would be
> used to
> figure out the cost.
> vehicle_type might be helpful if
> there are
> multiple costs to
> traverse a link based on say, car,
> carpool, bus,
> truck, walking,
> taxi, etc. This could also be used
> to implement
> the rules
> for bus
> and train lines.
>
>
> I think one of the difficulties with routing
> topic is that
> everyone
> (also myself) immediately think about routing in
> terms of
> vehicle types.
> It's the easiest example to explain pgRouting,
> but I think
> one premise
> of pgRouting is that it should work for any kind
> of network.
> Let's say
> your network would be the human nervous system.
> What is a
> vehicle there?
> Well, probably changing "vehicle_type" to
> "speed" would make
> sense, right?
>
>
> Sorry for using vehicle as the selector maybe
> "service_type"
> would be better, but the point is not the name,
> "speed" is
> equally misleading, the point is to be able to be
> able to pass a
> selector to the under lying function so that based
> on the
> selector we can compute an appropriate cost.
>
> For my vehicle routing example, I chose: car,
> carpool, bus,
> truck, walking, taxi, etc. because these might have
> different
> rules associated to them. The selector values would be
> appropriate to the model that you were working with.
>
> car vs carpool vs bus - many cities have HOV lanes
> that bus and
> carpool can use but not single occupancy cars. We
> might want to
> allocate a higher speed to those lanes vs the normal
> lanes
> during rush hours. Emergency vehicles many be
> allowed to make
> u-turns on highways that other vehicles can not
> make. Trucks
> might be banned from some streets so need to be costed
> appropriately, etc.
>
> If we had a live traffic feed information linked to
> segment ids
> in another table, The cost function could be
> implemented to
> check that table and if a record exists then use that
> information or return the standard information. By
> keeping this
> data in a separate table that is presumably much
> smaller and
> dynamic than the street records it would make it
> much easier and
> more cost effective to make dynmaic changes to that
> table and to
> hide (abstract away complexity) by using a cost function
> supplied to the underlying code.
>
> -Steve
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