Any motor vehicle in use on a street shall be equipped
with, and required signal shall be given by, a signal lamp or mechanical
signal device when the distance from the center of the top of the
steering post to the left outside limit of the body, cab or load of
such motor vehicle exceeds twenty-four inches or when the distance
from the center of the top of the steering post to the rear limit
of the body or load thereof exceeds fourteen feet. The latter measurement
shall apply to any single vehicle and to any combination of vehicles.