Snow removal from sidewalks

I noticed that on Crooks Rd from 12 Mile to 13 Mile (East side), there are a lot of patches of sidewalk that have not been shoveled.  This includes business like gas stations, a grocery store and other businesses.  There are students that walk home from the middle school northward and from the high school southward that walk these sidewalks.  They were very icy today and have shown no signs of ever having the snow cleared since the storm.  On two occasions I've seen eldery women walking in the street to avoid the sidewalk.  Is there a city ordinance requiring shoveling snow off the sidewalks and if so, why isn't it being enforced?