How to find better solutions?

If you are finding it hard to come up with signal timings that work for the traffic flows you need to accommodate, here are a few tips that might help you towards a solution:

1.  Try a wider variety of cycle times, not just units of 10 seconds.

2. If you have any multiple cycled controllers, make sure the option “Equal Length Multiple Cycling is switched off.  This gives the optimisers the greatest freedom to find a solution.

3. Use either of TRANSYT 14’s or TRANSYT 15’s alternative optimisers – Shotgun hill-climb or Simulated Annealing:

Both optimisers take significantly longer to run, but will give better results in the majority of cases.  note also that both optimisers have parameters that can also be varied – for Simulated Annealing the higher the temperature and the slower it is set to cool will increase the time to run but will improve the chances of the best result.  For Shot-gun hill-climb the only parameter is how many starting points (runs) that you want – 10 runs will increase the time to run by 10, and so on.  Increasing the number of start points will increase the chances that a better solution is found.

4. If you don’t have TRANSYT 14 or TRANSYT 15 you are of course more limited in what you can do, but you can still increase the number of hillclimb increments, or if you have TRANSYT 13 or later, use the “Enhanced Optimisation” option which forces TRANSYT to repeat the full set of hill-climb increments until no further improvement occurs in the PI.  The “Extended -offsets and green spilts” optimisation level option can also be used as this adds extra items to the hill-climb list that makes bigger incremental changes to the green times – This increases the time to run only marginally, but the benefits are also relatively modest on average – The main reason for use of this option is for linking to microscopic models to ensure they react enough to the changes being made.

5. Try different stage sequences: New sequences can be easily added and stored in either TRANSYT 14 or TRANSYT 15.  These newer versions of TRANSYT have also inherited functionality from OSCADY PRO so phase and stage sequence optimisation can now be carried out on junctions within a TRANSYT network.  From the Timings Diagram use the menu option “Tools/Phase Optimiser/This Controller”.  This is a very powerful function that allows you to find the best solution for each individual controller.