The Waze client, and also the "live map" on the web site, hides smaller roads as you zoom out. This is fine in cities where there are many roads. However, in rural areas, the small roads are simetimes the only roads, and if they are hidden then the map can appear completely blank.

I suggest changing to an algorithm that takes the amount of clutter into account. Something like "first disply the major highways; if the screen is not yet too cluttered then also display the minor highways; if the screen is not yet too cluttered then also display the major roads; if the screen is not yet too cluttered then also display the ordinary roads; if the screen is not yet too cluttered then also display the small roads, parking lot roads, private roads, 4x4 tracks, etc."