Currently the newest series of CTA rapid transit fleet, the 5000-series train cars are equipped with AC propulsion; interior security cameras; aisle-facing seating, which allow for greater passenger capacity; LED destination signs, interior readouts, and interior maps; GPS; glow-in-the-dark evacuation signs; operator-controlled ventilation systems; among other features. AC propulsion allows for smoother acceleration, lower operational costs, less wear and tear, and greater energy efficiency. For DC propulsion, braking essentially means converting the excess kinetic energy into heat. AC propulsion can take advantage of regenerative braking, meaning the train returns excess energy to the third rail as it slows down.