Not sure whether this is just localise trait, but down my way there is a tendency for drivers to just choose their own speed limit. Either they speed or drive 10-15kph under. After getting stuck behind someone doing 85 in the 100 zone, then 60 in the next 100 zone (a dodgy that most people do 80), then 40 in the 60 zone, I really wondered what was going on with this driver?

I understand about road conditions, weather etc there are a number of road around here where you would be mad to actually drive at 100.
I understand driving at 95kph as it is generally the most fuel efficient speed.
I understand the tractors and other farm equipment.

But to be honest, I can't understand the average driver, in the average car.

So if you regularly drive below the speed limit, or know of someone who does, can you explain why? I really do want to understand in the hope that it keeps me a bit calmer on the road