The Regional Transportation District (RTD) of Denver recently demonstrated a new automatic braking system on its light-rail trains.

The automatic train-stop (ATS) systems are designed to sound an alarm, and slow and stop a train if an operator moves a train through a red signal. RTD plans to spend $3 million to install the systems on 117 older light-rail cars by year’s end. The 55 cars RTD is purchasing for the FasTracks program will feature factory-installed ATS systems.

The ATS systems will serve as a backup to RTD’s automatic block signaling system, the “principal means for keeping trains apart,” agency officials said in a prepared statement.

Meanwhile, Juanita Chacon on Tuesday announced she’s leaving RTD’s board for professional and personal reasons. A realtor, Chacon was appointed to the board in August 2005 and elected to a four-year term in November 2006. Denver Mayor John Hickenlooper and his staff will seek a replacement for the board seat.