Waze is a mixed blessing as it can help you navigate around traffic jams and reach your destination faster than you have any right to expect, but it also has resulted in vast amounts of traffic through neighborhoods and intersections with smaller streets and traffic controls that weren't designed to handle the number of cars suddenly being routed through them.
I have long been suspicious of Waze's algorithms. For instance, when routing around a traffic jam, does it choose different routes for different users to spread the traffic out? Does it select particular routes in order to glean traffic data from them, even though they may not be the most efficient? Do they take into account the amount of traffic for which a road or intersection is rated?
I think it behooves Waze to work with cities to identify problem traffic areas that have arisen specifically because of their users (one such intersection is right by my office, where thousands of cars are directed through a large residential neighborhood daily in order to avoid traffic backup on the highway, but that traffic is backed up from the same intersection where this flow of rerouted cars ends up rejoining the highway. The situation has made it so there's a 15-minute wait just to pull out of my office parking lot at peak times. I would like to see Waze build in some protections from situations like this, as they are actively working against the transportation design goals of municipalities everywhere.