I also wonder if it could be CBTC. "Investment" to me = money spent on something new and some sort of new process/system.

I'm not sure if I would classify as going back to the old ATO system as an "investment" given that it would just involve seeking approvals from the WMSC, training/re-training operators on ATO, etc.

In a tweet, Clarke said "Our team is working on getting 🚇 back to operating on ATO as it’s safer. Top transit systems in the 🌏 run some level of ATO. We are also working on CBTC & we will analyze platform screen doors for full modernization."

WMATA already has an office (IIRC) that deals with the transition to CBTC, and the VP of said office (Tiffani Jenkins, Vice President Signaling System Renewal Program (SSRP)) just gave a presentation at a conference that dealt with CBTC last month.

I could see the agency installing CBTC on the Red Line first, before producing to other lines throughout the system.