They'll be able to hold a third more riders.
The project is pretty straightforward: expand platforms at 28 different DART stations, so three-car trains, instead of two-car trains, can run there.
DART's Director of External Relations, Gordon Shattles, says during the workday commute, cars on the Red Line and Blue Line, are full.
"At peak times we try to keep right at about 165 people for the max carrying capacity on each one of our cars," he said. "And I'll tell you as anyone who's had an opportunity to ride them knows, it's standing room only, especially during peak."
The Red Line runs from southwestern Dallas up to Plano. The Blue Line runs from South Dallas to Rowlett.
DART actually broke ground on the project three weeks ago. The total price tag is just under $129 million. The Texas Department of Transportation is kicking in $60 million and DART is contributing $8 million of its own funds. Construction should be complete by the end of 2021.