The police superintendent, in consultation with the city engineer, shall designate and mark off such individual parking spaces as necessary along city streets or property. It is unlawful to park any vehicle parallel to or across lines or markings painted upon the curb or street to designate a parking space in such a manner that it takes up more than two (2) parking spaces in the Downtown Commercial zoning district which is defined in Exhibit A below. No person may park any commercial vehicle having the length of twenty-two (22) feet or more, inclusive of the front or rear bumpers, or park a commercial vehicle coupled to a trailer or semi-trailer having the length of twenty-two (22) feet or more, inclusive of front or rear bumpers, in the Downtown Commercial zoning district at any time except when such parking is necessary or required while carrying out a lawful commercial purpose. The parking of noncommercial vehicles which exceed the weight and length limits stated above is allowed in public areas which are designated with the appropriate signage.