Think a positive test guarantees discipline? This arbitration ruling says otherwise
A workplace vehicle accident. A positive urine test. A 30-day unpaid suspension, mandatory drug assessments, and random testing — all thrown out.
In a February 12, 2026, award, Arbitrator Graham J. Clarke ruled that Toronto Terminals Railway Company (TTR) had no just cause to discipline a signal maintainer who tested positive for THC metabolites after a workplace incident, because TTR failed to prove he was actually impaired on the job. For HR professionals relying on blanket cannabis prohibition policies, the message is clear: a positive urine test alone is not enough.
One accident, one policy, one expensive decision
On September 13, 2023, signal maintainer DiMaria had a workplace vehicle accident. He exited his vehicle without putting it in park; getting back in, he accidentally hit the accelerator instead of the brake, causing a collision that damaged the company vehicle and public property. TTR conducted post-incident testing immediately.
The breathalyzer and oral fluid swab came back negative. The urine test returned THC metabolites at 33 ng/ml. TTR cited violations of its internal Policy 1.4, specifically its provisions on Drugs, Illicit, Illegal and Legal Drugs and Mood-Altering Substances, Recreational Cannabis, its 28-Day Cannabis Ban, and the employee obligation to "report for duty in a condition that enables them to perform their duties safely and effectively."
On September 27, 2023, TTR issued a 30-day unpaid suspension. It also required DiMaria to complete a substance abuse professional assessment and submit to random drug testing before returning to work, conditions tied directly to the disciplinary notice.
The drug test that didn't prove enough
DiMaria told investigators he had consumed cannabis two or three days before the incident — a small joint, a few puffs, on what was possibly a workday Monday. Clarke applied a well-established line of arbitral decisions separating employees who work while impaired from those who work while unimpaired, giving significant weight to the negative oral fluid swab result.
TTR's own post-incident Form 104 noted DiMaria's nervousness but checked "normal" for Balance/Walking, Eyes, Skin, and Awareness. No boxes were marked for Smell of Alcohol or Marijuana, Shaking/Trembling of hands, or Slow or inappropriate actions. Clarke found the nervousness unsurprising given DiMaria had just had an accident.
As Clarke wrote: "Unfortunately, accidents happen and can warrant discipline. But they do not, by themselves, support a finding of impairment."
When the discipline itself cannot stand
TTR argued that DiMaria's unusual conduct during the accident, combined with his positive urine result, pointed to residual impairment. Clarke rejected this, finding the evidence did not clear the threshold required to apply the more serious "impaired" line of cases and their corresponding penalties. Without just cause for the suspension itself, the SAP assessments, random testing requirements, and Continuing Employment Contract were all rescinded alongside it.
The arbitrator's order was unambiguous: "The arbitrator therefore rescinds all the discipline. TTR shall provide full compensation for the 30-day suspension. TTR shall also compensate Mr. DiMaria for the time he spent doing assessments and attending drug testing."
Clarke anchored his conclusion in a consistent line of arbitral authority. As established in CROA&DR 4524, a decision Clarke expressly relied upon, "it is not enough to show that a urine test indicates an employee may have traces of marijuana in his/her system. Those results do not demonstrate impairment at the material times."
