Demand/Shortest or Optimal Path Routing
Contents
Introduction
DUAROUTER can be used to import demand data given by source and destination edges (so called trips and flows ). Furthermore, it can be used to repair an existing route-file i.e. if a given route has an unconnected edge list. To achieve dynamic user assignment, DUAROUTER and SUMO must be called iteratively. This is described in Demand/Dynamic User Assignment. Beginning with version 0.29.0, DUAROUTER also supports IntermodalRouting.
The trip and flow elements described below may also be loaded directly into SUMO. This takes up-to date traffic states within the network into account when computing routes but slows down the simulation.
Trip Definitions
Trip definitions that can be laid into the network may be supplied to the router using an XML-file. The syntax of a single trip definition is: <trip id="<ID>" depart="
Attribute Name | Value Type | Description |
---|---|---|
id | id (string) | The name of vehicles that will be generated using this trip definition (a running number if not given) |
depart | int | The departure time of the (first) vehicle which is generated using this trip definition |
from | edge id | The name of the edge the route starts at; the edge must be a part of the used network |
to | edge id | The name of the edge the route ends at; the edge must be a part of the used network |
via | edge ids | List of intermediate edge ids which shall be part of the route; the edges must be a part of the used network |
fromTaz | district id | The name of the district the route starts at. TAZ edges are selected so that travel time is minimized. |
toTaz | district id | The name of the district the route ends at. TAZ edges are selected so that travel time is minimized. |
color | color | This generated vehicle's color |
departLane | int/string (≥0,"random","free","departlane") | The lane on which the vehicle shall be inserted |
departPos | float(m)/string ("random","free","random_free","base") | The position at which the vehicle shall enter the net; "free" means the point closest to the start of the departlane where it is possible to insert the vehicle. "random_free" tries forcefully to find a free random position and if that fails, places the vehicle at the next "free" position. "base" sets the vehicle's depart position to the vehicle's length + eps (eps=.1m), this means the vehicle is completely at the begin of the depart lane. |
departSpeed | float(m/s)/string (≥0,"random","max") | The speed with which the vehicle shall enter the network. |
arrivalLane | int/string (≥0,"current") | The lane at which the vehicle shall leave the network |
arrivalPos | float(m)/string (≥0(1),"random","max") | The position at which the vehicle shall leave the network |
arrivalSpeed | float(m/s)/string (≥0,"current") | The speed with which the vehicle shall leave the network |
If any trips use the type attribute, the referenced vType element must be put into the trip.xml file or into an additionally loaded rou.xml-file or into an additional-file.
By default, DUAROUTER will write vType definitions into the output route file ahead of the first vehicle using that type. By using the option --vtype-output these definitions can be put into another file.
Flow Definitions
Flow amounts share most of the parameter with trip definitions. The syntax is: <flow id="<ID>" from="<ORIGIN_EDGE_ID>" to="<DESTINATION_EDGE_ID>" begin="<INTERVAL_BEGIN>" end="<INTERVAL_END>" number="<VEHICLES_TO_INSERT>" [type="<VEHICLE_TYPE>"] [color="<COLOR>"]/>. Notice the following differences: the vehicle does not take a certain departure time as not only one vehicle is described by this parameter, but a set of, given within the attribute "number". The departure times are spread uniformly within the time interval described by <INTERVAL_BEGIN> and <INTERVAL_END>. All these three attributes must be integer values. Flow definitions can also be embedded into an interval tag. In this case one can (but does not have to) leave the tags begin and end out. So the following two snipples mean the same:
<flows> <flow id="0" from="edge0" to="edge1" begin="0" end="3600" number="100"/> </flows>
and
<flows> <interval begin="0" end="3600"> <flow id="0" from="edge0" to="edge1" number="100"/> </interval> </flows>
Let's review flow parameter:
Attribute Name | Value Type | Description |
---|---|---|
id | id (string) | The name of vehicles that will be generated using this trip definition; vehicles and routes will be named "<id>_<RUNNING>" where <RUNNING> is a number starting at 0 and increased for each vehicle. |
from | edge id | The name of the edge the routes start at; the edge must be a part of the used network |
to(1) | edge id | The name of an the edge the routes end at; the edge must be a part of the used network |
via | edge ids | List of intermediate edge ids which shall be part of the route; the edges must be a part of the used network |
type | type id | The type id of the vehicles to generate |
begin | int | The begin time for the described interval |
end | int | The end time for the interval; must be greater than <begin>; vehicles will be inserted between <begin> and <end>-1 |
number | int | The number of vehicles that shall be inserted during this interval |
color | color | Defines the color of the vehicles and their routes |
departLane | int/string (≥0,"random","free","departlane") | The lane on which the vehicle shall be inserted |
departPos | float(m)/string ("random","free","random_free","base") | The position at which the vehicle shall enter the net; "free" means the point closest to the start of the departlane where it is possible to insert the vehicle. "random_free" tries forcefully to find a free random position and if that fails, places the vehicle at the next "free" position. "base" sets the vehicle's depart position to the vehicle's length + eps (eps=.1m), this means the vehicle is completely at the begin of the depart lane. |
departSpeed | float(m/s)/string (≥0,"random","max") | The speed with which the vehicle shall enter the network. |
arrivalLane | int/string (≥0,"current") | The lane at which the vehicle shall leave the network |
arrivalPos | float(m)/string (≥0(1),"random","max") | The position at which the vehicle shall leave the network |
arrivalSpeed | float(m/s)/string (≥0,"current") | The speed with which the vehicle shall leave the network |
(1) JTRROUTER does not need this parameter, DUAROUTER requires it
Custom edge weights
The option --weight-files <FILE> can be used to affect the weights used during routing. The input format conforms to the output format of the edge based traffic measures. By default this uses the traveltime attribute of edges. The option --weight-attribute <STRING> can be used to use other attributes for routing. Weight files that only contain some of the network edges are permitted. If undefined, the traveltime of an edge defaults to the free-flow traveltime. Also, only the weight-attribute must be defined:
<meandata> <interval begin="0" end="3600" id="whatever"> <edge id="edgeID1" traveltime="23"/> <edge id="edgeID2" traveltime="1000"/> </interval> </meandata>
Usage Examples
duarouter --trip-files trips.xml --net-file road.net.xml --output-file result.rou.xml
the file trips.xml given below must contain edges contained in the network file road.net.xml .
<trips> <trip id="1625993_25" depart="25" from="-15229224#3" to="4474184"/> <trip id="1542480_35" depart="35" from="-46771582" to="-24038909#1"/> <trip id="1544282_35" depart="35" from="20554351#2" to="-4876083#5"/> <trip id="1565407_35" depart="35" from="-25771472#1" to="-25160470#0"/> <trip id="1620115_45" depart="45" from="11279351#3" to="5198584#1"/> <trip id="1647560_45" depart="45" from="54048879#0" to="-52105434#0"/> <trip id="3761248_45" depart="45" from="-31928311" to="23792451#7"/> </trips>
Trips may contain source and destination districts as well as edges. If the
districts shall be used for routing this has to be specified using the option "--with-taz". Furthermore (if the net does not contain the districts) a districts file needs to be provided:
duarouter --trip-files=<TRIP_DEFS> --net-file=<SUMO_NET> \ --output-file=MySUMORoutes.rou.xml --taz-files=<DISTRICTS> --with-taz
The edge weights are ignored when using TAZ this way. Instead TAZ edges are selected so that the travel time is minimzed.
As we have to read in the flow definitions completely into the memory - something we do not have to do necessarily with trips, an extra parameter (-f or --flows) is used to make them known by the router:
duarouter --flows=<FLOW_DEFS> --net=<SUMO_NET> \ --output-file=MySUMORoutes.rou.xml -b <UINT> -e <UINT>
Remind that one can not insert flow descriptions into a trip definitions file. The opposite (some trip definitions within a flow descriptions file) is possible. You also can give both files at the input file, for example:
duarouter --flows=<FLOW_DEFS> --trip-files=<TRIP_DEFS> --net=<SUMO_NET> \ --output-file=MySUMORoutes.rou.xml -b <UINT> -e <UINT>
Dealing with Errors During Routing
When running DUAROUTER you may encounter errors of the type
Error: No connection between 'edge1' and 'edge2' found
This is caused be an unconnected network. If your network has vehicle class restrictions it may be that the connectivity is only lacking for particular vehicle classes which is less obvious from the GUI. You can ignore these routes using the option --ignore-errors. However, if a large proportion of your routes cause this error you should definitely investigate your network file for problems. The tool Tools/Net#netcheck.py can be used to pin down the connectivity gaps in your network.