SR 05:276 - Laserfiche WebLink

. , I I Typical Modern Compact Urban Roundabouts I I I I I I I I I As shown in the preceding photographs and diagram, the intersections with roundabouts are I about 110 feet across as measured diagonally from comer to comer. The internal circle is 70 feet I in diameter and is bounded by a three-inch high mountable curb. The outer 10 feet of the center ~ island is constructed with decorative colored and textured concrete. This allows the rear tires of large semi-trailer commercial trucks and residential moving vans to enter this area when making left or u-turns around the circle without damaging landscaping or irrigation systems. The inner I landscaped portion of the circle is 50 feet in diameter. The outer portion of the landscaped circle is usually planted with turf or other very low-growing plants. The central area of the circle can be planted with large shrubs and trees or can have other entry features such as fountains or gateway signing. The following table from the Federal Highway Administration Roundabout Design Guidelines I book shows that not only are the total number of traffic collisions reduced when roundabouts are constructed, but the most significant reductions are in the number of injury collisions. Constructing roundabouts at these locations should eliminate the need to consider more expensive traffic signal controls at any of these intersections in the future, and should significantly reduce concerns about vehicle speeds adjacent to the park and residential areas. Averaae annual crash freauencies at 11 U.S. intersections converted to roundabouts Type of Before Roundabout With Roundabout Percent Chanqe Roundabout Sites Total Injury PD~ Total Injury PD~ Total Injury PD~ Single-Lane 8 4.8 2.2 2.6 2.4 0.6 1.8 -50% -73% -31% Multilane 3 21.5 5.8 15.7 15.3 4.0 11.3 -29% -31% -28% Total 11 9.3 3.0 6.3 5.9 1.5 4.4 -37% -50% -30% PDO - Property Damage Only collisions Vineyard Corridor Development SR:01:171 Page 4