No person shall park a vehicle in an alley, except for the purpose of loading or unloading, and then only during the time necessary to load or unload, which shall not exceed one-half hour. This section shall not apply to merchants' delivery trucks parked in alleys immediately at the rear of their respective places of business if such trucks are parked so as not to obstruct the passing of moving cars therein. Every vehicle, while loading or unloading in any alley, shall be parked in such a manner as will cause the least obstruction possible to traffic in such alley.
(1958 Code § 16.72)