City of Thibodaux Zoning Review - South Central Planning ...

Thibodaux Zoning Review 2010Visibility at IntersectionsAnother concern mentioned during our discussions with thecity’s staff was regarding the visibility at intersections in residentialareas. Typically zoning ordinances will limit the heights ofvegetation, fences, signs and other structures at street intersectionsso a motorist’s view of oncoming traffic is not blocked. Thisis a safety matter. The area within which vegetation and structuresare limited is referred to as a “sight triangle”. Thibodauxstaff expressed concern relative to the lack of clarity in the waythe city ordinance describes how to create the sight triangle. Thecurrent method used is to pivot from the center of an intersectionand to strike an arc radius at 50 feet. This arc would thendetermine the area in which nothing can be built or located ina manner that results in obstruction of a motorist’s view in alldirections. In comparing the current restriction to the other likecommunities, Thibodaux’s current practice is more prohibitivethan the others as it provides a greater distance, which createsgreater clearances. However, the area that must remain withoutobstructions is literally determined by the width of the street.Meaning the smaller the street, the greater the sight clearance,and vice versa, the greater the street width the smaller the nonobstructionarea. During discussions between SCPDC and thecity’s staff, it became apparent that the general rule for calculatingthe sight triangle may be inappropriate at intersectionsthat do not intersect at perfect 90 degree angles. The Thibodauxstaff found the ordinance language especially difficult to employat a number of intersections where one or more diagonal streetsintersected streets laid out in a grid pattern. Himalaya Street wasnoted as an example.City Thibodaux ZoningThe directions for calculating the sight triangle within theThibodaux ordinance are found in two places. In the definitionof a sight triangle, the city outlines the method for calculating aright triangle using 150 feet along intersecting streets. Also, thedefinition of “Yard” reinforces the notion that heights are limitedwhere visibility might be obstructed.Article XVIII. DefinitionsSight triangle: An area adjacent to street intersectionsmaintained clear of visual obstructions; a triangle soconstructed that two (2) sides thereof are superimposedupon the intersecting street centerlines for a distance of onehundred fifty (150) feet back from the point of intersectionof the centerlines, the third and closing side terminating atthe respective points one hundred fifty (150) feet from thepoint of centerline intersection.Yard: A required open space measured from the buildingwall with a maximum overhang of two (2) feet other than acourt unoccupied and unobstructed by a structure or portionof a structure from thirty (30) inches above the generalground level of the graded lot upward, provided however thatfences, walls, poles, posts, and other customary yard accessories,ornaments, and furniture may be permitted in anyyard subject to height limitations and requirements limitingobstruction of visibility.An illustration is included that shows how the sight triangleshould be drawn using the definition in the Thibodaux ordinance.The Thibodaux zoning ordinance continues with explanationsand restrictions regarding the height of structures and vegetationin the sight triangle in several places. However, in residentialzones the right triangle created to ascertain the sight clearancearea is shortened to 50 feet on two sides so the clear area is alsosmaller.“Sec. 601. Visibility at intersections in residential districts.On a corner lot in any residential district, nothing shall beerected, placed, planted, or allowed to grow in such a manneras materially to impede vision between a height of 2 1/2 and10 feet above the center line grades of the intersecting streetsin the area bounded by the street lines of such corner lots anda line joining points along said street lines 50 feet from thepoint of the intersection.2005.1. Visual obstruction: Signs in a sight triangle shall notobscure vision between heights between three (3) and seven(7) feet above grade.”38