Alyth Yard Calgary Alberta - Changes in traffic control methods over a stretch of track damaged during the 2013 flood in Calgary contributed to a 2016 freight train collision, says the Transportation Safety Board (TSB) in Investigation Report R16C0065 issued Wednesday.
 
Just after 09:20 on 3 Sep 2016 Canadian Pacific train 303 was rolling westbound into CP's Alyth rail yard when, after rounding a corner, it encountered a stationary train on the tracks head.
 
Despite a prompt emergency brake application, the almost 2.5 kilometre long train slammed into the rear of the stopped train, toppling a number of cars and sending two derailed locomotives into the dirt along Ogden Road near 50th Avenue S.E.
 
Nobody was seriously injured in the collision.
 
According to the accident report, train 303 had received instructions to enter Alyth yard behind a second train, which had arrived about 30 minutes earlier to swap crews.
 
A short time later, the decision was made to delay the first train's departure to allow another train to depart ahead of it, a delay the report says wasn't passed on to 303's crew.
 
About 09:17 train 303 passed a green signal in Ogden to proceed onto unsignalled track through the yard, non-main track territory that under Canadian rail operating rules requires operation at speeds permitting stopping within one-half of their field of vision, and not exceeding 24 km/h.
 
Radio conversations overheard by 303's crew, as well as the clear signal they'd just passed, led them to believe the train ahead was several kilometres down the line, prompting the conductor to radio the crew of the train ahead to confirm its position.
 
The yardmaster replied, saying the train ahead had not yet departed the yard, which prompted 303's engineer to immediately apply the train's brakes.
 
But, by then, the train was 330 metres from the stationary train and moving too fast to avoid a collision.
 
Analysis by the TSB suggests the train needed at least twice that distance to safely come to a stop.
 
One factor in the collision, the TSB report states, were changes to railway traffic control along the stretch after the 2013 floods.
 
The June 2013 collapse of the Bonnybrook railway bridge in the flood-swollen Bow River prompted railway officials to take the existing Centralized Traffic Control (CTC) system offline, re-designating the nearly five kilometre section as non-main track while carrying out repairs.
 
Once repairs were complete the following April, the stretch retained its designation as non-main track, while maintaining its previous speed limit of 72 km/h.
 
Under CTC rules, indications by trackside signal lights convey information about the track ahead, specifically if occupied by another train.
 
The report suggests the crew's observation of a green signal at Ogden may have misled them about the track ahead being clear, when in fact the signal's authority ended at a small sign 15 metres away.
 
Railway rules at the time permitted trains, upon passing a green signal, to transition from controlled to non-controlled territory at a posted speed limit of 72 km/h.
 
Crews interviewed by the TSB reported confusion over train handling requirements through the stretch, with some engineers opting to operate at speeds significantly slower than the posted 72 km/h speed limit.
 
In September 2016, Canadian Pacific restored CTC to the affected stretch of track, and implemented a 32 km/h speed limit on yard tracks adjacent to the collision site.
 
Bryan Passifiume.