Track diagrams are included for signaled lines, wherever possible. Track diagrams are not included where information is unreliable. Information was obtained in the following ways:
Actual observations, usually from riding trains over the lines.
Railroad track charts.
CORA (Chicago Operating Rules Association) guide, dated 2011.
Metra Operations Profiles.
Google satellite imagery.
Information is subject to change, and is usually verified more regularly for passenger railroads and railroads closer to Chicago.
Google satellite imagery is the newest method used to obtain information, and theoretically makes it possible to create track diagrams of almost any railroad in the world. But the quality of the imagery varies among areas, and cannot always be used.
All main tracks are shown, along with most switches within interlockings, and other tracks used by main line trains. Not shown are hand operated industrial switches.
The following colors are used to indicate types of operation:
BLUE - manual interlocking
RED - centralized traffic control (CTC) or bidirectional signals
GREEN - automatic block signals
BLACK - unsignaled
Thin or faint lines across tracks indicate signals. In CTC or bidirectional signal territory, signals usually exist for both directions at all locations, except at interlockings where the signals usually are only in the direction entering the interlocking.