Online update of OTP Graph

[Antonio Bucchiarone]

Dear members.
I would like to understand if there is someone had an experience to update the OTP graph on-the-fly. We need to udpate information like: blocked streets, not available bus stop, etc..
Since I'm using OTP in a real-time application I would like to update the graph every time we have such a notification and in a such a way that OTP will plan using and updated version of the graph.

Thanks a lot in advance
Antonio

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[Andrew Byrd]

Hi Antonio,

There are several different ways of updating the graph in OTP. Some ways actually modify the graph structure, while others update auxiliary data structures like public transit timetables that are referenced by the graph during searches.

For public transit, OTP supports GTFS-RT trip updates. These can be loaded from a file or a URL, or provided in a continuous stream (differential mode) over websockets. For streets, some work has been done on dynamically changing street speeds.

There is some information (including example configuration files) in the OTP documentation:

http://opentripplanner.readthedocs.io/en/latest/Configuration/#real-time-data

There is not really any documentation on the speed updaters because that is a very experimental system built against an early version of OpenTraffic. If you’re writing your own code though that could be adapted to updating speeds or even blocking traversal of certain roads. The example class is:

org.opentripplanner.updater.traffic.OpenTrafficUpdater

The shared mechanism that would need to be used by a custom speed updater is:

graph.streetSpeedSource.setSnapshot(new StreetSpeedSnapshot(speedIndex));

You can see an example of this in org.opentripplanner.updater.traffic.OpenTrafficUpdater.

If you are looking for more specific information about configuration or extension points, you will need to be much more specific about what you’re trying to do and what data sources you’re using for people to be able to help you.

Regards,

Andrew

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[Antonio Bucchiarone]

Thanks Andrew,
is there any example on how the OpenTrafficUpdater can be used? For example 1) where the TrafficInformation are memorized to be used and with which format? 2) how the traffic info are used ? 3) are the OTP resulting plans have this information ?

Thanks a lot
Antonio

Andrew

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[Andrew Byrd]

Hello,

To my knowledge there are no examples, and you probably cannot use this code as-is. I would take it as an obsolete unsupported prototype.

The only way you will be able to use it is to work directly on the source code and build your own system inspired by the existing code. Where and how the traffic data are stored would be your own choice. I am not quite sure what kind of information you are seeking when you ask “how the traffic info are used”. I could say they are used to set the speeds on graph edges for routing, but that doesn’t tell you anything you don’t already know.

If you want to do the things you’re describing with OTP, you will need to work directly on the source code and trace the execution to understand how it works, or create a project to do so with other people. If this is outside the technical capacity of you, your organization, your subcontractors or collaborators, OTP is probably not suitable for the task at hand.

-Andrew

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[Antonio Bucchiarone]

Dear Andrew, Dear All
I'm implementing my updater following your suggestions. Thanks a lot.

To understand how the OTP plan method uses the speed factor to avoid zero speed edges, can you suggest the class or the piece of code where this is done now in the planning phase?

Moreover, where the trip alternatives are generated? Could be they more then one or OTP returns only one solution?

Many Thanks
Antonio