Runs as required

This field determined whether a train has a probability of not running. At it's simplest if you want a single train to not always make an appearance then tick the box 'Runs as required' and the set the % probability of it running.

Where it gets more complicated is if you have mutually exclusive trains. Here you need to be aware of the laws of precedence as that will dictate how you set the probability.

Ignoring delays for the time being

For example you have two trains and equal probability of running.

Where you have n trains with equal probability of running.

Work out which train will be T1 and set that to have the required probability (50%) then leave T2 as 100% and write the notif rules. The test will then be whether T1 runs and if so T2 will not or if the test says T1 not to run then by default T2 will run. It T2 is not set at 100% then there is a probability that neither will run

Train T1 should be given (1/n)% T2=(1/(n-1))% and so on. So three mutually exclusive trains will have T1=33%, T2=50% and T3=100%

Considering delays

[Can't get this to align!]

If the delays for each train are such the the order of precedence remains as before then everything will work as desired. However, of the delay results in the erstwhile T2 becoming T1 then as it has 100% probability of running it will and the relevant NotIf rule will hold back the other train. I suspect that this will affect the relative probabilities of each train running but the NotIf rules will maintain the single entry either way.

Last edited by GeoffM on 15/09/2016 at 03:01