it is 30cm per 100m....431m is approx 1.3m wide
(400 = 1.2 and 500 = 1.5, take 1/3 of 100 about 33m give one 1.3m)
The drivers testing in Ontario is a joke and like my friend says" It's not you I worry about, it's the other guy".
Got that right!
So what do the rest of the officers at your detachment think is fair??? We have black and white speed limits here in Ontario.......grey enforcement............

I think every officer in my office would stop someone that passes a marked patrol vehicle.
I can not directly speak for others on their tolerance per se. I do not ride with anyone else to see their style either. Anytime I have stopped with another officer and asked the seen the person stopped, it is always greater than 20 above the limit.
As I'm sure you can appreciate, I would rather stop someone for a higher speed than a lower, in particular where demerit points will be added. We do not have enough officers to stop everyone at 1km over, so where would do we start? Pick off the 105km? 110? etc..
Only option would be to go back to photo radar in moving mode (so people just don't slow down at one point) and ticket every vehicle over the posted limit.
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca