Definitely a speed trap. Northbound you go around the curving underpass under Lawrence, and suddenly you are on a bridge. The speed limit is 10 km less, because bridges are liable to icing. Your trip is on a Sunday morning in August, when there is no traffic or ice, but that doesn't change the law. There has been no warning signage about the change. I've been ticketed here for going 15 clicks over. The only defense is to stay in the centre lane, and hope they're too busy pulling people over from the curb lane. August, of course, is a month when the city is quiet, so it's hard to make your quota!!