PTV Visum - Frequently Asked Questions (FAQs)
PrT or PuT demand has not been assigned completely. How can I analyse this to find out where and why this happens?
A typical error message can be:
'DUE could not assign .. OD pairs completely or partially, e.g. due to closures or for too low capacities.'
You can analyse this by using a 'Remaining matrix', indicating the amount of not assigned demand per relation:
Since PTV Visum15: Use a matrix of Data source type 'Formula matrix' to calculate the Remainder matrix. In the dialog 'Edit formula...' the following functions are combined to an expression referencing the demand segment code to calculate the Remainder matrix:
Until PTV Visum 14: Matrices -> (select a matrix with only partially assigned demand) -> (open the context menu with the right mouse button) -> Save to file -> Dialog 'Save: Matrix' -> Dialog 'Save matrix ..:
Format: 'Format V' or 'Binary'
Matrix: Assignment matrix
Option: activate the option 'Remaining matrix' (only available for assigned matrices)
This matrix can be opened as an external matrix. Filter it on values > 0.
Check the following reasons when demand has not been assigned completely:
A) PuT assignments:
- Missing connections.
- Rounding of volumes: Calculate -> General procedure settings -> PuT settings -> Assignment -> Round demand and volume data (active) -> Number of decimal places
B) PrT (only in case of Dynamic assignments):
2) In case of DUE network coding errors like:
- missing connectors.
- wrong attribute values on links and connectors.
- defective topology (not connected nodes covering the same location).
- impedance too high (lacking capacity, volume too high).