In TRANSYT 15 a number of task list messages are presented as “Warnings” if auto-redistribute is enabled, and as an error when it is not. This is because there is an expectation that the auto-redistribution process will fix the timings prior to the main optimisation process starting. As long as there only warnings reported, TRANSYT will not prevent the optimiser running, irrespective of the outcome of the auto redistribution process. This means that it is entirely possible that the optimised solution can still exhibit unresolved phase constraints. Stage minimums can never be broken by the optimiser, so these are not an issue here.
This all leads me to the advise in the title of this FAQ – If after optimising the network, these phase constraints are still broken, then this suggests that either there is no solution out there that satisfies the various signal timing constraints, e.g. cycle time, inter-stages and stage minimums, or a solution is too hard for the optimiser to find. In this situation you should be treating these warnings, as errors that require attention. After all you set these constraints on the model – if you still believe them to be correct why would you accept timings that break them?
The solution is to re-examine the various constraints and ensure that they are all required at the values used, e.g. can a phase minimum be reduced? or can the cycle time be increased to accommodate all the constraints? You can use the “Repair Timings” timing diagram option to check if there is a solution that does not break the constraints, as this is equivalent to the auto-redistribution process.