The Transportation Safety Board learned bus drivers made a habit of speeding on Transitway, north of the Barrhaven rail crossing where the deadly bus-train crash happened in 2013, to make up time on their schedules.

But the city disputed that finding, telling the TSB in private that there is no issue with lost time because OC Transpo has scheduled routes so that drivers don't have to speed.

The disagreement between the two organizations is exposed in the comments the city sent to the TSB during the draft report phase of the investigation.

The Sun obtained the documents through access-to-information.

The TSB, getting the last word in the draft report phase, suggested there was a culture of speeding in that area, based on what investigators heard during interviews.

"During these interviews, it was indicated that it was not uncommon for drivers to exceed the posted speed limit and use the Transitway to make up some time," the TSB wrote back to the city.

The TSB's final report, released to the public last Wednesday, listed the point under the "causes and contributing factors" of the crash.

Drivers are under pressure to maintain a schedule to meet passengers' expectations, the TSB's report says.

The double-decker that struck the Via Rail train on Sept. 18, 2013 -- resulting in the death of the driver and five passengers on the bus -- was on time by Transpo's standards.

It was running three minutes and 48 seconds over the scheduled time.

"On time" at Transpo means being within five minutes after the scheduled time. (Being early is more of a no-no since there's a risk of leaving passengers behind.)

The TSB raised a concern about the lack of speed enforcement on the Transitway before the crash.

Between Sept. 18, 2011 and Sept. 17, 2013, special constables only did speed enforcement six times, but no formal records were kept on the number of speed tests completed.

In that period, the 53 buses were speeding. Verbal follow-up only happened three times.

The TSB did its own speed tests on the Transitway near the crash site on four days in June 2014.

Investigators discovered between 21 and 31% of buses were travelling above the speed limit.

On Sept. 24, 2014, Transpo announced publicly it started daily speed enforcement on the Transitway.

Speeding is tracked and "appropriate corrective action" is taken, the city told the TSB.

The Transitway is governed by a bylaw, not the Highway Traffic Act, and drivers could be subject to discipline because of speeding.

The city says it has no authority to put bylaw infractions on the driving licence records of bus drivers.

The TSB acknowledged Transpo's explanation about what on-time performance means, but the agency suggested it's concerned about the pressures drivers face to keep a schedule.

"Given the percentage of drivers observed to be speeding on the Transitway, it may be beneficial for OC Transpo to determine why this occurs," the TSB told the city.

Twitter: @JonathanWilling