What is the purpose of classification lights?

[Ulrich]

Some are three or four lights arranged in a row.. some are arranged in a triangle.. what's the purpose?

[Randy Stahl]

The arrangement doesn't mean a thing. White to the front indicates an extra train, green to the front indicates another section following and red is a marker for a trailing engine.

[CSSHEGEWISCH]

Classification lights (or flags) date back to operation by timetable and train order.  Green lights indicate a following section of that schedule, all sections except the last section would display green. White lights indicate an extra train.  Red lights serve as rear-end markers.  Their function is virtually obsolete and except for rear-end markers they are rarely displayed.

[BaltACD]

Most, if not all Class 1 US carriers have eliminated class lights, where they previously existed on many engines have had that area plated over.

[Buslist]

Class lights were an essential part of timetable and train order operation. But since we don't operate that way any more they are no longer needed.

[cx500]

I've heard the reason for plating existing class lights over is somewhat bizarre.  They are not needed, BUT if they exist and a bulb is burnt out, it is considered a safety defect under government rules.   The fact that the bulb is redundant and will not be used is irrelevant - it must be fixed before the locomotive is used.

[Norm48327]

They fit into what we in aviation call a "minimum equipment list". If they are installed, they must be working, hence either removing them or plating over them.

[BaltACD]

cx500

I've heard the reason for plating existing class lights over is somewhat bizarre.  They are not needed, BUT if they exist and a bulb is burnt out, it is considered a safety defect under government rules.   The fact that the bulb is redundant and will not be used is irrelevant - it must be fixed before the locomotive is used.

FRA regulations - a device may not be required - but if supplied it must be operational.

[NorthWest]

I believe that there was an FRA order somewhere in the late '80s/early '90s. This is why the red oscillating emergency lights on SP locomotives disappeared so quickly, as most of them probably didn't work (considering SP maintenance practices) and were too expensive to repair.

Conrail continued to purchase locomotives with class lights for a long time after others had stopped, and recent CN locomotives still have marker lights, but I don't think they operate in any color but red.