Investigations found that human error and a design flaw in the mechanical safety devices caused this accident.

Many of the seriously injured were extracted from the twisted remains of the most damaged subway cars by rescue workers who worked through the evening under extremely hot and humid conditions.

At locations such as downgrades, curves, and switches, the same signals additionally serve to enforce speed limits.

With the tolerant attitudes of management, it had become common practice for operators to travel at the fastest speed that the system allowed, passing the signals at the same instant they were clearing.

In any case, he believed that grade timing was in use and so approached signal SP71 at the same speed as he would normally drive on this section.

The "trip" or "train stop" consists of a T-shaped arm placed just outside the right-hand rail near each signal (except a repeater).

On the relevant class of trains, the trip valve is located near the centre of the right side of the leading bogie, where its position in relation to the rail is well controlled.

Wismer and Becker, Inc., the contractors who installed the signal system on the Spadina line portion of the subway, chose to use an Ericsson train stop that was designed to have the trip arm located in the middle of the track.

A subcontractor, Gayle Manufacturing, designed a mechanical extension that would allow the device to drive a trip arm in its actual position outside of the rail.

However, with normal wear of the wheels and rails, and with the train rounding a curve at speed (and therefore riding off-centre) it was another matter.

[6] The TTC acted quickly following the accident to repair the defective modified Ericsson train stops.

The trip arm remains up during this phase, but the flashing red confirms to the driver that there was a lunar white on entry to the section and that the signal can be expected to clear at any moment.

[citation needed] In 2003, Toronto's Tarragon Theatre premiered Russell Hill, a theatrical play by Chris Earle about the impact of the disaster on several characters.