Ever since COVID-19 reached Chicago in early 2020 and CTA ridership plummeted, transit riders have voiced concerns about rising violent crime and less sanitary conditions on the system. But another major issue has been unreliable bus and train service due to pandemic-related labor shortages, which is at least as important for restoring ridership.

The CTA has tried to address the staffing shortage by doing a better job of retaining and recruiting workers. These efforts included the February approval of a new contract with the transit workers union that included raises and retroactive hazard pay for hours worked in 2020.

But long and unpredictable waits between runs continue to be a problem. For example, mobile developer Fabio Göttlicher,  recently analyzed Blue Line Train Tracker data and found that between early December 2021 and late April of this year the CTA had only been running about half of its scheduled Blue Line service.

This is reminding me that I probably need to leave a half hour earlier than the before times to get to the Sox game tonight. @cta, when you are losing dedicated transit advocates, then you might be toying with complete system collapse. No more headways more than 10 minutes. EVER.

— Jacob Peters (@ArchiJake) May 25, 2022

Particularly aggravating has been the phenomenon of “ghost” trains and buses to the now-common situation where train or bus runs appear the Train Tracker and Bus Tracker, but then disappear before they ever arrive. Not having enough operators for all the scheduled runs is somewhat understandable. But giving customers false hope through with inaccurate arrival times seems inexcusable.

That’s been an issue for me for months. One example: 36 bus starts at LaSalle St. station. 2 wks ago I had 2 ghost buses in a row at a.m. rush hr. Next bus came. Asked driver what happened to other 2. He said “no drivers, so those buses aren’t running.”

— aka60643🐈‍⬛🇺🇦🌻 (@aka60643) October 21, 2021

More than a month after Streetsblog asked the CTA for an explanation of the the ghost train and bus problem, this week the agency finally got back to us. “It’s a complex subject,” a spokesperson explained shortly before we received the full statement. “We’re trying to come up with the most-accurate language for you and your readers.”

According to the CTA’s statement, the trackers use “a combination of real-time vehicle location data (by GPS, track and/or other sensors), historical travel time data, and schedule-based info to generate the best possible estimated arrival/departure times with available data.”

However, the agency said several factors can mess up the accuracy of trackers (their language):

• A trip being adjusted or cancelled to balance service following a delay
• A staffing availability issue that affects schedule adherence
• A reroute or delay on a line that slows or stops service
• A missed terminal departure for any reason (Operator availability, reassignment of resources, a train experiencing an equipment problem, etc.)
• Equipment failures or technological limitations, such as poor cellular connections or malfunctioning GPS units

“Any of these conditions can create a situation in which a bus or train will appear on a tracker, but then disappear, which some refer to as a ‘ghost bus’ or ‘ghost train,'” the CTA stated. “This happens because arrival estimates are continuously updated based on the best data we have. For example, when new vehicle location data becomes available, that sometimes replaces or is used to adjust schedule-based data. (Vehicle location data is only available once a trip starts, so we must supplement it with schedule-based data so that riders boarding at or near the beginning of a route or on routes with longer headways have enough information to plan their trips.)”

So what makes a bus or train disappear from the tracker? “The answer depends on whether the vehicle is a bus or a train, whether the prediction is based on real-time vehicle location or the schedule, and whether the app or sign being viewed is layering additional logic or supplementary data on top of what is supplied by us,” the agency said.

Here’s an example scenario the CTA provided. Let’s say it’s 1:00 p.m., and an Orange Line train is scheduled to leave Midway Airport at 1:10.

You’re standing on the platform of the Pulaski Orange station, the first stop from Midway, watching the arrival time screen. The next estimated arrival on the display is 1:12 p.m., because it usually takes two minutes for a train to travel from Midway to Pulaski.

Now it’s 1:11 p.m. and a train hasn’t left Midway. The tracker allows some slop for slightly late departures, so the arrival is still listed as “<1 min” at Pulaski.

But a little while later, if a train still hasn’t left the airport, the tracker system will assume that run is cancelled. The trip will be removed from the tracker, and subsequent schedule-based arrival estimates will be displayed with “—” to indicate that a trip is expected soon, but that the level of uncertainty is high enough that the tracker isn’t going to even hazard a guess of when the train will arrive.

As soon as a real-live train leaves Midway, live vehicle location data becomes available and the predictions across the Orange Line will refresh based on that new info, the CTA said. The first arrival estimate shown on the digital signs will be based on that live vehicle location, but the one after that will be from the schedule,

“We understand that situations where estimates end up being incorrect are extremely frustrating to any rider,” the agency said. “That’s why we continually work with vendors to improve the systems behind-the-scenes that power arrival times; how information is represented on our website and in our app; and to find ways to better anticipate and mitigate when unplanned service disruptions or staffing issues temporarily impact service schedules.  We are fully committed to providing the best travel tools possible.”

We need @cta to get fully staffed to run all the service scheduled and to work with @cdot to develop true bus rapid transit corridors to ensure reliable service that people can depend on. https://t.co/txAQhEMaHd

— Audrey Wennink (@awennink) May 26, 2022

Active Transportation Alliance spokesperson Kyle Whitehead wasn’t impressed by the explainer. “CTA’s focus on the technology distracts from the unfortunate reality that bus and train service is often unreliable in Chicago, leading to more and more ghost trains and buses. As a city and a region, we need to be investing in long overdue upgrades to bus and train service to improve speed and reliability.”

Whitehead said transit upgrades should include giving buses priority on the street with a citywide network of dedicated bus lanes and bus rapid transit on major bus corridors. “The Better Streets for Buses planning process and wealth of federal funding available provides opportunity to transform Chicago’s bus service – if elected and agency officials are willing.”