When it comes to designing a yard for your model railroad, give some thought to how you’ll keep the activities of your yard switcher separated from passing trains on the main line. If your layout plans include running through trains simultaneously with switching a yard, you’ll quickly find you run into a problem. Specifically, if you don’t do some advance planning, a traffic jam will occur when a train approaches the yard and confronts the yard switcher on the main pulling a cut of cars. Yard jobs are dead last on the food chain, and by rule, should clear for the higher class train. If there is any volume of traffic at all, the poor yard job has to constantly stop working and wait for the main to clear. The solution is what is called a drill track. A drill track is nothing more than a long lead parallel to the main that allows the switcher to work away, totally clear of the main line. Although available space won’t always allow it, ideally the drill track should be as long as the longest yard track. If you’re in the midst of planning the yards on your layout, working a drill track into the yard design can go a long way towards streamlining future operations.
Should there be more than one operator on the system it is important that the classification of rail cars does not interfere with the through freight or passenger train that is on the main line. The drill track or yard lead should be twice as long as the longest yard track thus allowing two tracks to be pulled in order that proper sorting is done. You cannot sort if you can only pull one track.