A southbound Red Line train. by Matt’ Johnson licensed under Creative Commons.

Finally, some good news for Metrorail riders: WMATA is planning to restore computer-driven trains in June of 2019, just under a decade after the system was turned off following a fatal collision of two Red Line trains outside of Fort Totten. The return of “auto doors,” the process where doors automatically open once a train properly berths at a station, should also be returning as early as this coming November.

A return to Automatic Train Operation (ATO) is a win for riders because it keeps trains more evenly-spaced, helps them stay on schedule better, and produces a smoother ride. For Metro, its return means less work for its rail controllers, potentially less power draw, and lower wear and tear on the agency’s rail cars.

Metro had computer-driven trains — until an accident

WMATA disabled ATO on June 23, 2009 in a knee-jerk reaction after a Red Line train crashed into the back of another, killing eight riders and a train operator. ATO wasn’t at fault, but the underlying system that controls train locations and keeps them separated was. Faulty track equipment susceptible to a thing called “parasitic oscillation” allowed the system to lose track of where the lead train was, and the following train wasn’t told to slow down in time.

Metro was built for the automation provided by ATO and ran with it since the system opened. Automated rail operations allowed the agency to consolidate and centralize around a single rail control center which controls nearly everything including the trains, power, fans, and more.

WMATA planned to restore ATO once before, in 2015, and got as far as turning the system on on the Red Line before turning it off just a few months later. Then-new General Manager Paul Weidefeld wanted to focus on more high-priority issues first rather than trying to return the entire system (not just eight-car trains) to ATO.

Metro wanted to reprogram all trains, whether six or eight cars in length, to pull all the way forward on the platform. Six-car trains used to stop in the center, leaving an even amount of space on either side of the train. “By the time ATO returns to the rest of the system in 2017, Stessel told GGWash back in 2015, ”Metro may be close to operating 100% 8-car trains anyway,” which would’ve made that a non-issue.

Not all trains will run in ATO all of the time

This time around, Metro paid a consultant to help them determine if they could restore ATO safely. One of the primary concerns keeping ATO from returning was a rule change implemented back in 2016 by Metro’s Chief Safety Officer Pat Lavin. The new rule meant trains could no longer go as fast as 35 miles per hour while passing workers on the tracks; now they had to slow down to 10 mph.

That speed limit is being raised to 15 mph, which goes into effect in November. The 10 mph limit was an issue because that specific speed is not enforceable by the ATC system. Metro’s rail controllers in the ROCC can only set eight different levels of speed and acceleration centrally, and a 10 mph limit isn’t one of them.

ATO will only be allowed during morning and evening rush hours, according to a source with knowledge of the agency’s plans who is not authorized to speak publicly about them. Workers are typically not allowed to be on the tracks during these times, so there would be no conflict between the ATO system and protecting the roadway workers.

Outside of rush hours, Metro is planning on using another subsystem, Automatic Train Supervision, to force trains that might errantly be running in ATO to operate no faster than 15 mph.

In case you're getting confused by these acronyms, here's a quick overview. Automatic Train Control (ATC) has three subsystems: ATO, which we've already discussed, Automatic Train Protection (ATP), and Automatic Train Supervision (ATS). ATO is the one that drives the trains, while ATS automatically slows trains down to keep them better spaced. ATP is what forces trains to slow down, whether they're in ATO or manual mode.

Rail controllers can use “Performance Levels” (PLs) to remotely limit either how fast trains can run in certain locations, or how fast they’re allowed to accelerate. One of these PLs (PL4) will be reprogrammed throughout the system to broadcast the updated 15 mph limit to trains during the times Metro requires ATO to be off and trains operated in manual mode.

It’s not clear how Metro’s pilot rollout of armbands that alert track workers of oncoming trains plays into the decision to limit ATO to rush hours only. The system is slated to be installed in 13 locations and used beginning July 2019.

Automatic doors will save time

Before the automated trains are back, Metro also wants its trains’ doors to open automatically. The agency moved away from auto doors back in 2008 after power system interference led doors on four trains to open on the wrong side off the platform.

With that problem since resolved, reimplementing automated doors means the several-second period train operators are required to wait before opening their doors can go by the wayside. The “Three to Five Second Rule” was intended to help ensure operators don’t open train doors on the wrong side, although that has continued to happen as recently as this year.

The extra wait imposed at every station became such a burden that Metro built that extra time into its schedules in 2017. Waiting five seconds at each station for each train adds up, and helped contribute to some trains running behind their schedule. Train operators will continue to close the doors manually.

ATO for now, CBTC for the future?

Metro’s Automatic Train Supervision system dates back to when the system was first opened. The system works when it’s well maintained, but it’s not as flexible as newer technology that’s come out in more recent years. Communications-Based Train Control is one of those new system standards that allows for better central control of train operations, as well as more granular control of how those trains operate.

The ATC system is built around hundreds of track circuits which split Metro’s 234 miles into sections hundreds of feet in length. If a section — or “block” — is occupied by a train, no other train can be nearby. The circuits use audio waves to run signals through the two tracks which trains run on top of. If one of the tracks breaks or if the signals don’t get through from the transmitter to the receiver, then trains will stop and have to request permission from the ROCC to get through the area.

CBTC is typically wireless-based, on the other hand: equipment mounted inside Metro’s tunnels transmits location, speed, and other information to and from the trains running nearby. The track can be split into smaller sections allowing Metro to run trains more closely-spaced, and it can give the ROCC more flexibility to control the speed and acceleration of trains.

The equipment in Metro’s ATC system is beginning to age, and the agency would likely need to spend several hundred million dollars to upgrade a good amount to keep it in good condition or move to the next version of the hardware. All track circuits were replaced after the 2009 collision.

Upgrading to CBTC would likely be a massive upgrade; the Bay Area Rapid Transit system is spending more than $1 billion to upgrade to the system, and New York City’s MTA has included upgrading most rail lines to CBTC in their $40 billion Fast Forward program. Metro could upgrade, but no funding for moves in that direction have yet been identified. Making the decision to go to CBTC sets the tone for the next phase of Metro’s train control system; staying with ATC simply means the agency would need to maintain and iterate on the system already in place.

After implementing the partial return to ATO, let’s hope that Metro becomes more comfortable running in the automated mode again, which can lead to further expansion of ATO at all hours.

Stephen Repetski is a Virginia native and has lived in the Fairfax area for over 20 years. He has a BS in Applied Networking and Systems Administration from Rochester Institute of Technology and works in Information Technology. Learning about, discussing, and analyzing transit (especially planes and trains) is a hobby he enjoys.