MEDFORD — In a train yard by Wellington Station, Governor Charlie Baker and several top MBTA officials toured a mockup of the next generation of Orange Line cars on Tuesday.

The new cars are part of a plan to replace more than 150 Orange Line cars and 250 Red Line cars by the summer of 2022, officials said.

Baker described the cars as an important element in upgrading and modernizing our public transport system. Stephanie Pollack, the state’s transportation secretary, said the larger cars will increase rider capacity by 40 percent during peak hours.

The new cars also come with technology and design improvements to make riders more comfortable, accessible, and safer, officials said. Doors are wider, some seats can fold up to provide more room, and computer screens provide route information.

The enhanced safety features include additional emergency intercoms by the doors, an advanced diagnostics system to detect potential problems, and closed-circuit video recording, officials said.

Six of the new cars will arrive in December and begin carrying riders in the summer of 2018, Pollack said.

Production of the 146 remaining Orange Line cars will begin in December 2018, officials said.

Delivery of the pilot Red Line cars will begin in March 2019, with 252 new cars to be delivered by June 2022.

Baker said the upgrades will bring the MBTA into the modern era.

“We’re really looking forward to putting these in transit,’’ he said.

Andrew Grant can be reached at andrew.grant@globe.com.