Denver Light Rail Signaling - Checking All the Boxes

From time to time I have brought up some of the quirks inherent to North American light rail signaling systems.  Because they exist in a regulatory and cost grey area (not really railroads, not really subways, able to stop on sight in traffic, etc) the signaling systems they employ tend to be very economical.  Well this past summer I traveled to Denver and rode around on its extensive light rail network.  There I noticed that the RTD light rail had methodically checked off every box on the light rail signaling checklist and I figured I should share it here.

1.) Missing Wrong Direction Signals 

See that little red circle?  Yeah, that's plated as a signal because the RTD's commitment to single direction ABS is so complete that all wrong direction movements need to get talked past the stop disc at the next interlocking.

2.) No Distinction Between Auto and Interlocking Signals.

See any difference between the ID plate on the interlocking signals in the first picture and the ABS signal in the second?  No?  Well that's par for the course on a light rail system.

3.) ATS

Light rail systems don't uniformly lack speed and signal enforcement.  They just opt for the budget versions.  RTD Light Rail has some sort of loop based ATS on its main line sections, but the operators weren't too helpful in providing the details on how it worked.  Of course where ATS proves impractical one gets a nice little sign.

4.)  Single Headed Signals.



Light rail systems hate confusing drivers with multiple signal heads, so flashing aspects warn of diverging movements.

5.) Vehicle, Signal Thyself

Dispatchers cost money, so LRVs simply set their destination and let track mounted sensors do the rest.

6.) New Lines, New Rules

How can consultants bill those hours if they just say to stick with the same old thing?  Of course the line that just opened in 2017 would have some new signal rules requiring a second head!

7.) US&S N-3's

You look hard enough around a large light rail system and you'll find a US&S style N-3 signal head 😏

Did I miss any?  Throw something in the comments and I'll see if I can find an RTD example ;-)