If you're cycling between UpTown Waterloo and Kitchener, there are a number of routs you can take. King street is the shortest but most dangerous rout because of traffic and the Iron Horse Trail is safer because you avoid cars but gets congested in the summer. Sometimes you need to find that sweet spot between road and pedestrian trail. The map on this page shows a good cycling rout that, with the exception of a short part of Belmont Ave. West, uses quiet residential streets. This way you get to avoid cars and let pedestrians and slower cyclists enjoy the Iron Horse.
Travelling between the University of Waterloo and downtown Kitchener takes about the same amount of time on all three of these routs. Some Alternative routs are shown for the beginning and end.