Metra Train 504 Derailment
On September 17, 2005, Metra Train 504 with 185 passengers was heading north in Chicago, IL on the west track of a double main line route. The train was in push mode and consisted of one cab car in the lead, four additional passenger cars, and a locomotive in the rear providing motive power. The train had departed Joliet, IL at about 7:24 AM and was enroute to the LaSalle Street Station in downtown Chicago.
Shortly before 8:35 AM, the train approached two sets of signals. The first signal was at milepost 5.39 and the second signal was at milepost 4.73. Just north of the signal at milepost 4.73 was a 10-mph right-hand crossover between the west and east tracks. The crossover was located near West 47th Street and South Federal Street in Chicago and was lined for the train to diverge from the west track onto the east track.
The engineer said he thought he observed Clear signals at both signal locations, but subsequent investigation showed that the distant signal (first signal) was indicating Approach Diverging and the home signal (second signal) was indicating Diverging Clear. The signal indications required the train to slow to the prescribed turnout speed of 10 mph before reaching the crossover. Instead, the train accelerated as it approached.
The train entered the crossover at approximately 70 mph and derailed and went into emergency braking after it traversed the crossover. The fourth car from the head end, trailer coach 7488, struck the south end of a steel girder of a through plate girder bridge that carried the tracks over West 47th Street. As a result of the impact with the girder, car 7488 became airborne and landed on the north side of the bridge. The train came to rest on the north side of the bridge. The result of the derailment and girder impact was that there were 129 injured persons requiring medical attention, 38 seriously injured persons requiring hospitalization, and two fatalities.
James Loumiet and JRLA were retained to reconstruct the derailment and to evaluate the dynamics of the car 7488 as a result of the girder impact. Mr. Loumiet was working with RailroadExperts.com team member Robert Halstead (signals) on the case.
Mr. Loumiet inspected the derailment site and crossover track and documented evidence at the site including wheel marks on the rail and ties and damaged rail spikes. From this information, Mr. Loumiet was able to determine that the point of derailment was approximately 53 feet north of the south switch points for the crossover at CP 48th Street. The point of derailment was evidenced by the wheel marks on ties in this area, the outward bending of the turnout closure rail, the lateral misalignment of the turnout, bent and broken spikes, and the lack of derailment evidence south of this point. Given the bending of the closure rail it is likely that each car in the train derailed at this location.
The mechanism of the derailment was the outward bending or overturning of the closure rail caused by the excessive centrifugal forces to the train?s left side that were created when the train entered the crossover at a speed well in excess of the crossover speed limit of 10 mph. The mechanism of the derailment was evidenced by the outward bending of the closure rail, the lateral misalignment of the turnout, and bent and broken spikes.
Mr. Loumiet evaluated the train?s event recorder data to determine the train's operation. Part of this evaluation included locating where on the event recorder data the derailment had occurred. The derailment was evidenced by a recorded speed change from 70 mph to 35 mph in one second.
A speed change of 35 mph in one second is well beyond the normal operational characteristics of the train and is indicative of a spin-down and lockup of the cab car wheels. Wheel spin-down and lockup is common in derailments where the combination of the loss of power to the traction motors, loss of wheel-rail contact, and application of train brakes causes one or more wheels to stop rotating due to the sudden loss of tractive forces and presence of retarding forces on the wheel(s). Because cab car 8570 was equipped with an axle generator on its? R2 wheel, train speed was measured by the event recorder using wheel rotation. As a result, when the train derailed, the associated rapid wheel spin-down of the R2 wheel was shown on the event recorder data as a large and sudden loss of train speed.
Mr. Loumiet also analyzed the post-derailment dynamics for car 7488 to determine linear and axial acceleration and motion of the car and its occupants. Of particular interest was the girder impact by car 7488 and its effect on the car and its occupants. Mr. Loumiet inspected the car and was able to calculate and quantify these effects and plot the trajectory of the car and the train. Using the event recorder data and the calculated trajectory data, Mr. Loumiet was able to provide a detailed analysis of the motion path of the train and of car 7488 for use in an animation. A small segment of the animation showing car 7488's girder impact and vault is provided below.