(a) No person shall stop, stand or park any vehicle upon a street, other than an alley, in such a manner or under such conditions as to leave available less than 10 feet of the 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 directed to by a police officer or traffic control signal.
(b) Except as otherwise provided by law, no person shall stop, stand or park a vehicle within an alley except while actually loading and unloading, and then only for a period not to exceed 30 minutes.