Choose to avoid or not to avoid narrow street
You should give wazers an option to avoid narrow streets or if someone feels comfortable in narrow streets, recommend him/her a route which goes through narrow streets (if its faster).
I live in town which is filled with narrow streets and waze never recommends me a route through them but they are often faster than main roads.
Maybe you could also add vehicle category "truck/big vehicle" which would avoid narrow streets automaticly.
Great thinking! The issue you raised has been addressed in a recent redesign. Hope you like it!