By Suzanne Le Mignot

CHICAGO (CBS) — CBS 2 has learned why a CTA Orange Line train derailed last week, causing pieces of wood and metal fasteners like these to rain down on the busy road and sidewalk below the tracks.

A CTA spokesperson says what happened on the tracks above me, was a parking brake caliper detached from the rail car, then the wheels of the third car on the train, hit the caliper, causing the derailment.

CTA spokesperson Brian Steele tells CBS 2 that a security camera shows just a subtle movement of train car. The operator was unaware one set of wheels came off track and the third car of the 200 ton train had one wheel riding on the ties

The wheel riding on the wooden ties caused debris and steel e-clips to fall onto Wells and Van Buren last Tuesday.

This is the third incident for the CTA in the past few months. In March, a motorman fell asleep at the wheel on approach at O’Hare, sending her train right up an escalator. Those nearby ran frantically to avoid the train. Then last November, a runaway train, rammed a train on the Blue Line.

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