The "L"'s operations have changed a great deal over time. In the context of this site, the subject of "operations" covers a number of topics: lines and routings, yards, towers, shops, signals... basically anything that has to do with how the elevated runs daily! All of this has seen a lot of changes, advances, and reworkings over the decades. Below are a list of topics and pages covering many aspects of "L" and CTA operations. It's a wide topic and will no doubt take some time to create pages for them all, but for the sake of completeness, we've listed everything we intend to eventually cover.

Lines & Routes | Yards & Shops | Towers & Junctions | Freight Operations
Signals & Markers | Traction Power | Run Numbers

Lines & Routes

Current Lines

Abandoned, Former & Non-Revenue Lines

North-South Through-Routings

West Side Through-Routings

The "Ravenston"

Express Operations

Yards & Shops

Current Facilities

Abandoned or Demolished Facilities

Towers & Junctions

The following towers and junctions are or were interlockings located along "L" lines, controlling important crossovers used in revenue service. Junctions controlled by hand-throw switches, minor mid-route crossovers and interlockings not normally used in daily revenue service, and most terminal interlockings are omitted. Towers and interlockings located at yards are also generally omitted, except for those that also were used for in-service passenger operations. For information on these installations, see appropriate yard pages above.

Freight Operations

Various types of freight and non-passenger items have been carried over the "L" over the years. Freight such as that typically associated mainline railroads -- large boxcars, coal gondolas, et cetera -- was carried by the "L" companies and CTA using special electric locomotives, and generally limited to the North Side north of Montrose Avenue. Interurbans like the North Shore Line and Chicago Aurora & Elgin carried both carload and less-than-carload freight from terminals along the "L" to points north and west of the "L" system.

Signals & Markers

Marker Lights

Markers are colored lights displayed on the front of "L" trains. The color combinations identify trains of each route to towermen, supervisors, and other employees. The lights were first introduced in the late 1940s with the 5000-series cars and were retrofit onto the 4000s as well.

Wayside Signals

A wayside signal is any signal of fixed location along the tracks. These can include spacing boards, semaphores, automatic block signals with colored signal aspects (e.g. lights), and automatic train control (also with colored signals).

Traction Power

An overview of how substations convert electricity from the local utility into the 600 volts that powers the "L", and of the design of the third rail shoes used on "L" trains.

Run Numbers

Run numbers on CTA rapid transit trains have existed for several decades and their presence has become more ubiquitous to riders since the advent of the automated announcement system, which announces them at periodic times along each route. Find out here how run numbers work, what the numbers mean, and their connection to the routes, trips and operators is.