You might want to jump on this thread and share your experience implementing Multimodal routing.
pgRouting does not support this currently. But in general you assessment of the problem is correct. I would add "stations" between the various networks. A station can be represented as an extra node the you have to go through when changing modes. and the edges between the station and the different networks can contain costs that are associated with changing modes. For example, changing between a car and a rental bike, might add some time and cost to park the car, walk to the rental place wait in a queue to rent the bike. Or at an airport, you could add 1-2 hours to park and clear security, or to pickup luggage and wait for a bus, taxis or retrieve your car.
If you are using scheduled modes of transportation, like buses, trains, airports, etc. then you need to have the schedule information and have rules like you have to arrive X minutes before departure to get tickets, etc. so you can assess that at the stations or transfer points. And during the routing process you have to establish a start time, and then track the current time as you progress along your route so you can determine wait time for the next scheduled transfer point. etc. Likewise if you have time dependent turn restrictions these can be applied as appropriately as the route progresses and time moves forward from the start time.
Hi,
i have been playing around with osm2pgrouting and pgrouting itself, i
have followed the pgrouting workshop and i have things more clear.
However i still have a few questions.
1. If we have a edge conection nodes A and B and the type of the way
that allow several tranvel modes (for example 'residential'), for
example bicicle and car, then 1 edge is created, rigth?
2. If i want to limit the type of ways used for routing, that can be
achieved by the SQL text sentence in the A* algorithm so it just
retrieve that types of ways, rigth?
3. Now, my problem. I don't want to limit the type of vehicle used, but
the cost of taking a road by car, cicling or by foot isn't the same, and
even more not all type of ways are suitable for all types of vehicles,
cars can't go through pedestrian ways. I want to calculate the cheapest
routing regardless the vehicle used. My first idea is to 'clone' edges
so i can create disjointed graphs.
For example A and B are nodes of a way type residential, then some
edeges are created 1 from A to B and vehicle Car, 2 from A to B and
vehicle Bike and 3 from A to B and vehicle foot (since is a residential
way). Now if i compute A* it should giveme the cheapest way and implicit
is the vehicle used.
Furthermore, supose 4 nodes, A, B, C, D:
A: sidewalk and bicicle line and rental bicicle
B: sidewalk
C sidewalk, bicicle line and rental bicicle
D: sidewalk, bicicleline and bicicle parking
raw costs (reverse al equal):
A - B: 10
A - C: 20
B - D: 10
C -D: 2
The topography looks:
A -- 10 ------B
| |
20 10
| |
C ---- 2 -------D
If the edeges are cloned depending the vechicle used, it looks like:
x0 : node is sidewalk. Cost multiplier 1 (doesn't modify cost)
x1: node is public bike. Cost multiplier 0.2 (divide cost by 5)
x2: node is private bike. Cost multiplier 0.2
A0 --- 10 ---- B0
| |
20 10
| |
C0 ---- 2 ----- D0
A1
|
4
|
C1
A2
|
4
|
C2 ----- 0.5 ... D2
And :
A0 - A1: 0 (cost)
C0 - C1: 0
D0 - C2: 0
Now if my initial state is A2 it implies i am in A with my private bike
so if my goal is C0 (by foot) i have to park by bike in D in order to
achieve the goal.
Or if initial state is A0 and goal state is C0 i would do: A0 - A1 - C1
- C0, so i have rented a public bike and i have also returned it.
Of course i'm aware that this increase the state space for A*, the other
aproach is to modify how A* expand nodes.
If you know a better approach to achieve this please share. If not, i
was planning to modify how the network topology is created, thats why i
ask in the first mail for a easy to used OSM XML libreary, and since
it's only for importing i don't really care about the programming language.
Maybe the easiest way is to modify osm2pgrouting so it imports the
topology i described?
Hope it's easy to inderstand.
Best regards.
Javier.
*De:* Stephen Woodbridge <woodbri@swoodbridge.com>
*Para:* pgrouting-users@lists.osgeo.org
*Enviado:* Jueves 9 de febrero de 2012 18:49
*Asunto:* Re: [pgrouting-users] Importing for multimodal routes
On 2/9/2012 11:00 AM, Javier Mr wrote:
> Hi,
>
> i'm planning to use pgRouting for multimodal routing. I know
there is a
> branch of pgRouting for MMPTR, but until i gather more
information about
> it i'm trying to avoid it.
>
> What i'm planning is to make several graph, each one for each type of
> vehicle, pedestrians, bikes, etc... and each line of bus, train,
subway,
> etc... Then connect this graphs by making edeges from, for example, a
> bus station to the closest pedestrian edege with length of 0.
This way i
> would have a big state set for the A* algorithm that should perform
> multimodal planing. Is there a reason why this shoulnd't be done?
>
> I have some doubts about how osm2pgrouting woks. I have seen that
OSM is
> capable of storing all this things, but i don't know if osm2pgrouting
> import all that into the DB, does it?.
>
> There are some libraries that work with OSM XML format, any in
> particular that you recomend?
There are a few tools that will load OSM data into a postgres databse
that pgRouting can use. You might want to read the documenation:
http://www.pgrouting.org/docs/tools.html
-Steve
_______________________________________________
Pgrouting-users mailing list
Pgrouting-users@lists.osgeo.org <mailto:Pgrouting-users@lists.osgeo.org>
http://lists.osgeo.org/mailman/listinfo/pgrouting-users
_______________________________________________
Pgrouting-users mailing list
Pgrouting-users@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/pgrouting-users
