VISSIM 5.30-05 User Manual

12.4 Traffic Demand
Traffic Demand
In Dynamic Assignment traffic demand is typically modeled using origindestination
matrices (OD matrices). Beyond that it is also possible to define
the demand in a trip chain file. It is also possible to mix both options.
Furthermore both options can be combined with traffic defined by vehicle
inputs and static routes (e.g. for pedestrian flows). However, this kind of
traffic is not affected by the Dynamic Assignment.
12.4.1 Origin-Destination Matrices (OD matrices)
The volume of traffic to be simulated in the network is specified as origindestination
matrices. Such an OD matrix contains the number of trips for
every pair of planning zones for a given time interval. For a simulation using
Dynamic Assignment, a number of matrices can be defined, each containing
demand information for a certain vehicle composition for a certain time
interval. Time intervals of different matrices may overlap arbitrarily; the
generated traffic for every moment comprises the vehicles from all the
matrices that include that moment in their time interval.
OD matrices are specified in the Dynamic Assignment window that can be
accessed by selecting TRAFFIC - DYNAMIC ASSIGNMENT...
Check the option Matrices to
activate the associated list box.
Use EDIT, NEW and DELETE to
define or edit an entry in the list
box or to remove it from the list.
A matrix is linked to a given vehicle composition, i.e. the trips of that matrix
are performed by vehicles randomly generated from the associated vehicle
composition. As explained in the section Parking lots, the desired speed
distribution for the generated vehicles is not taken from the composition
defined with the matrix but is overruled by the desired speed distribution
defined with the parking lot where the vehicle starts its trip.
The matrices cannot be edited directly using the VISSIM user interface but
are stored in text files and can be edited with standard text editors. The
matrices can be exchanged easily between VISSIM and VISUM via VISUM
export from VISSIM and ANM export from VISUM. However, these files can
also be created manually or converted from other transport planning
systems.
User Manual © PTV AG 2011 615