DOWNTOWN LOS ANGELES (KABC) -- Metrolink has unveiled its new Tier 4 locomotive, the first of 40 that will boast more power and lower emissions for the commuter train line.The new engines feature 57 percent more horsepower, designed to operate up to 125 mph, with what a designer calls the cleanest, most efficient and most powerful diesel-electric passenger locomotive in North America.The trains also reduce emissions of particulate matter and nitrogen oxide by up to 85 percent, according to Metrolink.They are also equipped with positive train control, an automated system that reduces human error by braking the train automatically if it senses an obstacle on the track or other dangerous situation.The trains cost about $280 million.