Shortest or Optimal Path Routing

# 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.

Note

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="" from="<ORIGIN_EDGE_ID>" to="<DESTINATION_EDGE_ID>" [type="<VEHICLE_TYPE>"] [color="<COLOR>"]/>`.

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. Optional, if one of the via-attributes is used or if the trip includes stops.
to | edge id | The name of the edge the route ends at; the edge must be a part of the used network. Optional, if one of the via-attributes is used or if the trip includes stops.
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.
type | type id | The type id of the vehicle to generate
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 Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes
arrivalPos | float(m)/string (≥0(1),"random","max") | The position at which the vehicle shall leave the network Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes
arrivalSpeed | float(m/s)/string (≥0,"current") | The speed with which the vehicle shall leave the network Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes
fromJunction | junction id | The junction from which to depart note
toJunction | junction id | The junction at which to arrive note
viaJunctions | junction ids | The junctions to pass along the way note
fromXY | float, float | The network position from which to depart note
toXY | float, float | The network position from which to depart note
viaXY | float, float [float,float] | The network positions to pass along the way note
fromLonLat | float, float | The network position from which to depart in geo-coordinates note
toLonLat | float, float | The network position from which to depart in geo-coordinates note
viaLonLat | float, float [float,float] | The network positions to pass along the way in geo-coordinates note

## Routing between Junctions

Trips and flows may use the attributes `fromJunction`, `toJunction`, and `viaJunctions` to describe origin, destination and intermediate locations. This is a special form of TAZ-routing and it must be enabled by either setting the duarouter option --junction-taz or by loading TAZ-definitions that use the respective junction IDs. When using option --junction-taz, all edges outgoing from a junction may be used at the origin and all edges incoming to a junction may be used to reach the intermediate and final junctions.

## Mapmatching

Since version 1.2 duarouter supports mapping positions to roads using attributes that end with 'XY' or 'LonLat'. The latter only works in networks that are geo-referenced. The maximum distance for map-matching can be configured using option --mapmatch.distance (since version 1.5)

Caution

SUMO does not yet support these mapping attributes.

By setting the option --mapmatch.junctions, positions are mapped to junctions instead of edges. The routes are then computed between junctions.

## Vehicle Types

If any trips use the `type` attribute, the referenced `vType` element must be put into the input file containting the trips / flow or into an additionally loaded rou.xml-file or into an additional-file.

Note

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 snippets mean the same:

    <routes>
        <flow id="0" from="edge0" to="edge1" begin="0" end="3600" number="100"/>
    </routes>

and

    <routes>
        <interval begin="0" end="3600">
            <flow id="0" from="edge0" to="edge1" number="100"/>
        </interval>
    </routes>

Note

The input file always needs a root level element to enclose the trip/flow elements and this should be named `<routes>`.

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
vehsPerHour | float(#/h) | number of vehicles per hour, equally spaced (not together with period or probability)
period | float(s) | insert equally spaced vehicles at that period (not together with vehsPerHour or probability)
probability | float([0,1]) | probability for emitting a vehicle each second (not together with vehsPerHour or period), see also Simulation/Randomness
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 Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes
arrivalPos | float(m)/string (≥0(1),"random","max") | The position at which the vehicle shall leave the network Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes
arrivalSpeed | float(m/s)/string (≥0,"current") | The speed with which the vehicle shall leave the network Note: see Definition of Vehicles, Vehicle Types, and Routes#Vehicles and Routes

(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>

# Repair routes

The --repair option intends to repair routes with connectivity problems. Depending on how the route is define, duarouter will try to fix it differently:

- If the route is defined with the "edges" attribute, duarouter will first try to fix the route by repairing the connectivity between the edges. If this is not possible, then duarouter will search for another valid route between the edges with connectivity problems. This may result in some edges from the original route no longer being on the new route. In other words, edges defined with the "edges" attribute are not taken as mandatory during route repair.
- If the route is defined with the "edges" attribute but also has "stops", duarouter will treat the edges of the stops as mandatory. First it will try to repair the route as in the previous example, but if duarouter cannot find a valid route that goes through the given stop edges, then the route is not possible to fix.
- If the route is defined with the attribute "via" edges, all edges will be treated as mandatory. If duarouter cannot fix the connectivity problems between the specified edges, a warning appears and the route is not repairable.

Duarouter also has the --repair.from and --repair.to options, which allow to fix an invalid starting or ending edge using the first or last usable edge of the route.

# Converting Input Styles

SUMO supports various styles of traffic demand defintions (vehicles, trips, flows) and duarouter can be used to convert between them.

- By default, duarouter will convert all inputs to vehicles with embedded routes (route as child element of the vehicle).
- With option --write-trips all input will be converted to trips
  - combined with option --write-trips.geo trips will be written with geo-coordinates (fromLonLat, toLonLat) instead of edges (from, to)
  - combined with option --write-trips.junctions trips will be written between junctions (fromJunction, toJunction)

# 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 ''.

    <routes>
        <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"/>
    </routes>

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

Caution

The edge weights are ignored when using TAZ this way. Instead TAZ edges are selected so that the travel time is minimized.

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#netcheckpy can be used to pin down the connectivity gaps in your network.

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