VISSIM 5.30-05 User Manual

12 Dynamic Assignment
12.9 Initial Solution from VISUM
As an initial solution for the Dynamic Assignment in VISSIM, the result of a
static VISUM assignment can be used. This aims on the reduction of the
number of iterations which are required in VISSIM until convergence is
reached. The VISUM assignment does not represent the final result but an
initial solution.
You can start the VISUM assignment in VISSIM. VISSIM provides two
possibilities:
► Automatic VISUM assignment calculation
► Manual VISUM assignment calculation
12.9.1 Automatic VISUM Assignment Calculation
In VISSIM, click menu TRAFFIC - DYNAMIC ASSIGNMENT - VISUM ASSIGNMENT to
start the automatic VISUM assignment calculation.
The VISUM assignment is calculated by means of the VISUM Converter
which is included in your VISSIM installation. Later the routes calculated in
VISUM will be stored in the automatically created VISSIM path file *.WEG.
The filename is derived from the PATH FILE entry in the Dynamic Assignment
window. From an existing path file with the same filename, a backup copy
*.BAK is generated prior to overriding.
Please note that your data files *.WEG and *.BAK are be replaced automatically
in case of multiple assignment calculations.
A static VISUM assignment in VISSIM requires significantly less time
compared to a microscopic VISSIM traffic simulation, which is caused by
the individual vehicles.
Once the VISUM assignment has been finished, the simulation (even a multirun
simulation) can be started immediately in VISSIM without any other work
steps. The first iteration uses the paths which were calculated in VISUM.
After the first iteration, the path file and the cost file created in VISSIM are
used. Their file names are retained.
No assignment can be calculated, if
the VISSIM network contains nodes
with a number that exceeds the
maximum permitted node number in
VISUM. For assignment calculation in
VISUM, the VISSIM node numbers
need to be edited in a way that they
no longer exceed the maximum
permitted VISUM node number.
648 VISSIM 5.30-05 © PTV AG 2011