Can you go 500 kilometers in 8 hours without driving faster than 55mph

Yes indeed !  You sure can. This is your lucky day.500 kilometers is about  310.7 miles.In order for you to cover that distance in 8 hours, you only need to average about  38.8 mph .  If you stop along the way ... for food, gas, rest, pits, etc. ... then you'll have to drive a little faster to keep up your average.  But by managing your stops, you can certainly do it without ever exceeding 55 mph.

Yes. 55mph equals 88.5139 kmph. in 8 hours, you will have traveled slightly over 700 kilometers.