No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, locking the ignition and removing the key, placing the transmission in park or the gears in low or reverse if the vehicle has a manual shift, or effectively setting the brakes thereon; and when standing upon any perceptible grade, turning the front wheels to the curb or side of the highway. (Prior Code § 42-14-3)