I have a model with three user classes, the model runs perfectly fine until I decided to implement crowding, I followed the steps as follows:
1- Coded the lines files by adding vehicle types, capacities (both seat and crush), load factor and the crowd curve for each line.
2- Coded the same info from above into the systemfiles, and added the crowd curves.
3- Modified my PT script to apply crowing.
It then hits me when i run the assignment with an error saying: "Crowd curve not specified for line vehicle type user class 1"
My understanding is that the crowd curve for that user class is not specified; which is not actually the case as I did add the vehicle type and it's correspondent crowd curve info in both levels (lines files and the systemfiles) and I did add the curves in the system files.
Does anyone have an idea why is this happening, or how could it be fixed?
Have you coded the CROWDCURVE into the VEHICLETYPE statement in the System file or the line file or both?
Perhaps you can post up your system file (.PTS) and an example PT line from the line file (.LIN)?
just wondering if you have added something like this in your system file?
VEHICLETYPE NUMBER=01 NAME="National Rail " SEATCAP=840,CRUSHCAP=1260,LOADDISTFAC=90,CROWDCURVE=01,CROWDCURVE=01,CROWDCURVE=01
you can see if you have 3 user classes, you need to specify crowdcurve, , and 
Thank you very much, in fact this is what I was missing, I was only specifying one crowdcurve thinking that it only requires one given that each user class relates to a certain vehicle type in my approach then cube would require only one curve; apparently I was wrong, anw thanks for your help.