A lap siding, in ProTrak, is defined by entering a negative number in the station interval datafield.

Open the "station edit" window.

On the pane "For "Interval" from previous station" (on the left),  in the datafield "Distance between clearance points", enter the distance as a negative number.  For example "-65".

In the list of stations, under the "Interval" column, for that station you will see "-65 lap".

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In the ProTrak Recipe Book, there is a diagram showing the definition of the "stations distances".  You can see there that by entering a negative number you are "sliding" the present station's siding back over the previous station's siding.

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Yes, the distance is used by the dispatcher functions.  However this distance is also used in the "tractive effort" and "train resistance" calculations within ProTrak, including the "car factor" value.

OK?

                 Jim