About 9:30 p.m. on Wednesday, March 7, 2007, the crew of CN Railway (CN) train R95491 left two locomotives, which had only air brakes applied, on a grade at the CN's interchange point at Lumber Street in Chicago, Illinois. The two uncontrolled and unmanned locomotives rolled to the north. They traveled from CN's track No. 4 onto Amtrak's track No. 4, where, at 9:56 p.m., they collided with the lead locomotive of standing Northern Illinois Regional Commuter Railroad (Metra) train 839. At the time of the collision, the event recorder data indicated, the speed of the runaway CN locomotives was 14 mph. They had traveled about 1,789 feet.
About 55 passengers were aboard the eighth Metra passenger car at the time of the collision. The other seven passenger cars were empty. Seven passengers and the Metra engineer and assistant conductor were transported to area hospitals with minor injuries; they were treated and released. The total property damage was estimated to be $75,766.