One of the main reasons we plan for alleyways is for placement of utilities and service access.  Garbage and fire trucks are the most common examples of services requiring access to a property from an alley.  Untrimmed trees and vegetation can be hazardous and inconvenient for our garbage collectors.  Owners are responsible for nuisance weed / vegetation control in the alley right-of-ways adjacent to their property (BMC 8.36).  Imagine if a garage were on fire and the fire truck could not get there due to illegal alley parking or obstruction.  Bozeman Municipal Code 12.12.020 states that alleys must be kept clear of obstructions and BMC 10.32.160 states parking cannot occur which prevents the free movement of vehicular traffic or blocks the driving entrance to any abutting property.