One way (not necessarily the only nor the best) would be to use the "Random" feature within the train's route.
Random Moves
You can also request that the program randomly reduce the number of desired car moves for a location. Use this feature if you find that the program is consistently generating the same amount of work for your train, and you want some variety. It is recommend that not use this feature until you find that is is needed. The "Random" column allows you to select a value between 10 and 100 and has a default of "Off" which disables this feature. The value is the percentage you want the move count reduced. For example, if you requested 20 moves for a location, and selected a random value of 10%, the program could reduce the desired move count by 2, which works out to desired car moves of 18, 19 or 20. A random value of 50% would reduce the moves by up to 10, or 10 to 20 desired car moves, and a value of 100% would generate desired car moves between 0 and 20. Note that small car moves need large random values to work properly. For example a desired car move of 1 will always be 1 unless you select 100% in the random column. A desired move count of 2 needs a random value equal or greater than 50% to reduce the move count by one, and 100% if you wanted the move count to be reduced by 2.
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If you select the "Random" percentage number for any given line of the Route, the program will occasionally reduce the total cars handled for the train when it is built...
