Visual obstructions to a motorist's view at the intersection of streets or driveways are not permitted at any time within any sight triangle, as specified herein. Such obstructions include but are not limited to any sign, hedge, fence, shrubbery, foliage, automobile or other object as determined by the Town of Islip, whether movable or stationary, which is higher than three feet and lower than eight feet above the adjacent edge of pavement. Such obstructions shall not include existing buildings, public utility poles, traffic control devices, natural grades, sign posts or small trees which do not exceed 12 inches in diameter or 38 inches in circumference and which are trimmed to the trunk leaving a clear area between three feet and eight feet above the adjacent edge of pavement as illustrated in Figure 404.