(a) No person shall stop, stand or park any vehicle upon a street, other than an alley, in such manner or under such conditions as to leave less than ten feet of width of the roadway for free movement of vehicular traffic, except that a driver may stop temporarily during the actual loading or unloading of passengers or when necessary in obedience to traffic regulations, official traffic-control devices or signals of a police officer.
(b) No person shall park a vehicle within an alley in such a manner or under such conditions as to leave available less than ten feet of the width of the roadway for free movement of vehicular traffic.