From WMATA:
“At the end of last month, we completed the installation of new barrier doors and higher fences at 10 stations as part of our fare system modernization program. Fare evasion has been reduced by at least 70% at these stations.
The aim is to complete installation at 10 stations by November.
Update: Number of stations to be determined. Starting in early October, more stations will be added, with a focus on major transfer stations with multiple entrances. ”