Why is it that dumpsters need permits to park in the street and

Wildwood - Why is it that dumpsters need permits to park in the street and can only be there for a limited amount of time, but construction trailers can park on a street indefinitely? There has been a construction trailer parked in the 200 block West Juniper Ave. for over a year now! There is also one parked in the 200 block West 26th Street that creates a major traffic hazard on a busy corner.