While I share your frustration, its a bit of a reach to file Art 37 over being "charged" with an accident.
The reality is that we are not entitled to safe driving recognition or awards per the contract. And the company is free to place whatever "black marks" it wishes to in our file.
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Should you be involved in another accident within 9 months and given notice of suspension, it is at that point that you could file a grievance for the suspension being unwarranted, and the merits of the original warning letter could then be debated. No rational grievance panel would ever uphold a suspension when the original warning letter was for a hit-while-parked incident such as the one you describe, and no rational Labor Manager would even bother taking such a pathetic case to panel in the first place.
One needs to develop the mental discipline to detach from any concern over being "charged" with these sort of bogus "accidents". Being "charged" for crap like this is no different from being "overallowed" on the daily report. Its nothing but a bunch of fiction for your management to make a big deal about, none of it matters, and you dont have to take it seriously or give a damn about it.