Calgary has a few traffic rules out-of-towners and new Calgarians need to know about.
School zones are marked with a sign showing children (silhouettes) walking to school. The end of a school zone has a sign without a graphic, just writing saying "End School Zone". On school days, the speed limit in a school zone is 30 km per hour, and there is no passing.
Playground zones are marked with a sign showing a child playing with a ball, again in silhouette. There is no passing in a playground zone. The speed limit is 30 km per hour. Playground zones are in effect every day, from 8:30 a.m. until "one hour after sunset". The end of the playground zone is marked with a sign.
The purpose of these zones is to protect Calgary's children. You never know when a kid will run across the street or suddenly appear from between some parked cars.
The speed of 30 km/hour is roughly the same as 18 miles per hour.