WMATA signaling

I know the WMATA system uses audio frequency block signals from the tracks. I know that intermittency of those signals was a cause of the red line accident near Takoma years ago. I know the new Silver Line segment has a different signaling manufacture than the rest of the system.

As I understand it WMATA cannot run more than a certain number of trains without traction upgrades (power).

Here is my question. If the system was designed today and cost was not a prime factor, what type of signaling system would be used on the trains or at least what would the options be? I know NY signaling is still terrible. But places like London seem to update ancient systems to modern ones.

Is this the most important investment to make in the system? A new east-west line? Better maintenance programs?

A whole new rebuild.

To be honest, if we were to start from scratch, money no object, I'd follow New York's system that they're rebuilding into: Radio-linked train control, cab signaling, backup wayside signaling in case the cab breaks and you're limping it back to the yard, four track operation (local/express lines).

Seriously. DC area needs express subway lines... and a hell of a lot more rail.

A few thoughts...

Intermittency doesn't adequately describe the cause of the 2009 Red Line collision. It was a combination of:
- Lack of maintenance that led to insulation breakdown on equipment racks in the train control rooms
- Incompetent maintenance and incompetent project management that led to track circuit transmit power levels being set to exceed design limits
- Overarching lack of safety culture that led to failures to identify and mitigate the above hazards which when combined with incompetent operating practices led to a catastrophic mass casualty event

The Silver Line segment does use equipment from different vendors, but there is already a mix of different generations and vendors throughout the rest of the system. The AF track circuit system is manufacturer agnostic because it's standards-based; the trains don't care who built the system as long as it complies with the specifications. This is just like how a USB thumb drive from any vendor works in any computer.

Traction power capacity is one limiting factor but the money to upgrade the entire system to 100% eight car train capacity was fully allocated in 2018. The upgrades are well underway and should be completed by 2026.

One thing to keep in mind about WMATA's signaling system is that it was built from the very beginning to be fully optimized for maximum throughput (the Silver Line being the exception). There is no gain to be made by changing technologies. We are already at the physical limit of capacity with the installed system. Other than traction power, which will be resolved shortly, the only remaining constraint is dwell time at stations. For WMATA specifically, this is where design sort of failed. Aesthetics won out over function in station layout which limits passenger circulation (think the inefficient characteristic U-shaped escalator layout in many underground stations).

When people talk about capacity gains from CBTC and other tech, they're usually talking about legacy systems that were built before AF track circuit technology. The New York Subway is an example of this. It was built with passive train control, then some portions were *retrofit* with AF track circuits. The thing about retrofit is that it's extremely expensive, and block design optimization will be compromised to reduce expense. Going from a retrofit AF-based system that wasn't optimized to CBTC will of course result in capacity gains. Again, WMATA was *built for* (rather than expensively retrofit) AF-based track circuits and the block sizes are already optimized. An upgrade to CBTC will not allow for more capacity.

Before the deadly 2009 Red line collision, WMATA nearly had a similar collision in a different part of the system.
- They knew that the automatic train control system was having problems, but didn't address it
- They knew the 1000 series were unsafe but did nothing to fix them and refuse to retire them saying they were short on railcars. Now with 7000 series out of service, we are much shorter on railcars

Back then, they didn't have any new cars. Those new cars are the 7000 series, and the 1000/4000/5000's are gone.

So yeah, those 8000's can't come fast enough.

STrRedWolf wrote: ↑Sat Jun 04, 2022 7:07 am A whole new rebuild.

To be honest, if we were to start from scratch, money no object, I'd follow New York's system that they're rebuilding into: Radio-linked train control, cab signaling, backup wayside signaling in case the cab breaks and you're limping it back to the yard, four track operation (local/express lines).

Seriously. DC area needs express subway lines... and a hell of a lot more rail.

I don't agree at all. WMATA in no way needs express trains. Look at London or Berlin. It should have a network first. Even NYC suffers a lot from the hub-spoke model. A less interlining and more lines overall is far better for the system, with just decent headways. People get more annoyed by headways than time on trains for the most part. Very few systems have any express sections. The London system sort of has a few skipped things but its very different from NYC. Quality of service then headways, then network effects.

The question wasn't a complete change to the system anyway it was only change to how it is signaled, not how it is constructed. This isn't a fantasy thing, you can resignal a line if its important enough.

dcmike
For WMATA specifically, this is where design sort of failed. Aesthetics won out over function in station layout which limits passenger circulation (think the inefficient characteristic U-shaped escalator layout in many underground stations).

When say the "U-shaped escalator layout" i am guessing you are referring to the stacked tuning fork entrance mezzanines that are only found in twin platform station. The layout of those mezzanines are designed to allow the flow of passengers between the entrance passageways and the platforms to not have to cross paths. The optimum fairgate setup is the have the faregates furthest from the station manager kiosk set for entry and the closet ones set for exit. The flow of passengers from up escalator heading to the exit faregates will be between the flow of passengers heading to the down escalator after passing through the faregates. The escalator heading to platforms are always the ones closest to faregates, the escalator for exiting the station are always the ones closet to the middle of the platform. The only exception to that rule is Crystal City.

It is my opinion that twin platform stations fitted with stacked tuning fork entrance mezzanines are superior to island platform stations with no fixed layout for the flow of passengers between the escalators / stairs ascending or descending between the platform and the entrance mezzanine passageway.

The reason why island platform stations are the predominant station design is because the station cost less to build and boring 2 single track tunnels between the stations costs less then twin box cut and cover or mining a 2 track tunnel.

drwho9437 wrote: ↑Fri Jun 03, 2022 4:15 pm As I understand it WMATA cannot run more than a certain number of trains without traction upgrades (power).

My understanding from Sand Box John and others on this forum is that WMATA struggles to run more trains because they don't have enough rolling stock, either to run more discrete trains or to run trains at the maximum length that each lettered route can support. If they are also having traction power restrictions then that is new information to me.

Someday WMATA might actually have enough rolling stock to run the proper number of cars per train and the proper number of trains that the signalling system, however suspect, can actually support. Until then my understanding was that the service level is well below the theoretical capacity of the system, minus the margins for dwell timings.

drwho9437
I know the WMATA system uses audio frequency block signals from the tracks. I know that intermittency of those signals was a cause of the red line accident near Takoma years ago. I know the new Silver Line segment has a different signaling manufacture than the rest of the system.

The original 103 mile system plus the 3 mile Blue line extension to Largo uses the GRS now Alstom automatic train control signal system designed to accommodate 90 second headways. Phase I of the Silver line branch also uses Alstom signaling system, only difference being it is designed to accommodate 185 second headways. Phase II of the Silver line branch uses US&S now Hitachi Rail STS signaling system that is also designed to accommodate 185 second headways.

As I understand it WMATA cannot run more than a certain number of trains without traction upgrades (power).

This only became an issue when WMATA began procuring rolling stock that was heavier then previous rolling stock procurement. The veritable frequency AC induction propulsion systems are also more power hungry then the older DC cam control and chopper propulsion systems. Later rolling stock procurement also had added systems in them that required more power.

WMATA has begun a program to increase the power output capacity at various traction power substation to allow the running of all 8 car trains.

Here is my question. If the system was designed today and cost was not a prime factor, what type of signaling system would be used on the trains or at least what would the options be? I know NY signaling is still terrible. But places like London seem to update ancient systems to modern ones.

WMATA signaling system is not he problem. The problem is loading demands that accedes the capacity at key locations along a given line. Closer headways creates higher capacity, Closer headways results in fewer passengers disembarking and boarding at those key locations allowing shorter dwell times. Procure more rolling stock to exploit the full capabilities of the existing signaling system, which WMATA has never done.

Is this the most important investment to make in the system? A new east-west line? Better maintenance programs?

Based on WMATA's track record a new east-west line would not solve the problem because they would inevitably not procure enough rolling stock exploit the full capabilities of its signaling system.

Better maintenance program, WMATA is showing they taking that route. They have added maintenance capacity at the shops in 4 of their 9 yards and are presently building a dedicated heavy repair and overhaul facility to do those tasks that are now being done in 2 of shops in other yards.

davinp wrote: ↑Sun Jun 05, 2022 8:22 am Before the deadly 2009 Red line collision, WMATA nearly had a similar collision in a different part of the system.

In the Potomac tube...

- They knew that the automatic train control system was having problems, but didn't address it

I know someone on the team in the tube that day They investigated it, but could not replicate it.They tried for
a significant length of time to no avail.

- They knew the 1000 series were unsafe but did nothing to fix them and refuse to retire them saying they were short on railcars. Now with 7000 series out of service, we are much shorter on railcars