See another of my posts about road vs street definitions. Note that a lot of suburban wide streets are built that way to meet fire codes written to accommodate overly-large trucks. A suburban town doesn't need giant trucks where smaller, cheaper, more maneuverable trucks can do the work. Combined with ubiquitous hydrants - which have disappeared from many US suburban subdivisions - they are more than enough fire safety for anything under 4 stories. Regulations to accommodate these huge trucks have helped ruin the human scale of streets in many places. Also note that existing old cities have become a lot more safe by using superior materials, installing sprinkler system, etc etc.