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Page 40 <br />ROUNDABOUT DESIGN GUIDELINES <br />Chapter 7 <br />Geometric Design Features <br />Figure 7/24a <br />Turning Widths Required for Normal Roundabouts <br />LEGEND <br />a Raised central island. <br />b Low profile mountable apron. <br />c Remaining circulatory roadway <br />width, 1.0 -1.2 times the maximum <br />entry width. <br />d Design vehicle. <br />e 1 meter clearance minimum. <br />f Inscribed circle diameter (ICD). <br />g Width between curbs. • <br />NOTE: Splitter islands should not <br />protrude into the inscribed circle if <br />the roundabout is designed tightly <br />as illustrated here, allowing only <br />the minimum width g. <br />29.0 <br />* Design vehicle requires a larger ICD (inscribed circle diameter) <br />Page 24 <br />Turning Widths Required for Normal Roundabouts <br />Meters <br />Feet <br />Design Vehicle <br />Inscribed Circle <br />Design Vehicle <br />Inscribed Circle <br />Bus <br />Diameter <br />STAA <br />Calif. <br />Bus <br />Diameter <br />STAA <br />Calif. <br />f <br />Min. g <br />Min. g <br />Min. g <br />f <br />Min. g <br />Min. g <br />Min. g <br />91.4 <br />6.7 <br />6.6 <br />5.2 <br />300 <br />22.0 <br />21.5. <br />17.0 <br />17.0 <br />85.3 <br />6.9 <br />6.6 <br />5.2 <br />280 <br />22.5 <br />21.5 <br />79.2 <br />7.2 <br />6.9 <br />5.2 <br />260 <br />23.5 <br />22.5 <br />17.0 <br />17.5 <br />73.2 <br />73 <br />7.0 <br />5.3 <br />240 <br />24.5 <br />23.0 <br />67.1 <br />7.8 <br />7.3 <br />5.3 <br />220 <br />25 5 <br />24.0 <br />17.5 <br />18.0 <br />61.0 <br />8.1 <br />7.6 <br />5.5 <br />200 <br />26.5 <br />25.0 <br />57.9 <br />8.4 <br />7.8 <br />5.5 <br />190 <br />27.5 <br />25.5 <br />18.0 <br />54.9 <br />8.7 <br />8.1 <br />5.6 <br />180 <br />28.5 <br />26.5 <br />18.5 <br />51.8 <br />9.0 <br />8.4 <br />5.8 <br />170 <br />29.5 <br />27.5 <br />19.0 <br />19.0 <br />48.8 <br />9.3 <br />8.7 <br />5.8 <br />160 <br />30.5 <br />28.5 <br />45.7 <br />9.8 <br />9.1 <br />5.9 <br />150 <br />32.0 <br />30.0 <br />19.5 <br />20.0 <br />42.7 <br />10.1 <br />9.6 <br />6.1 <br />140 <br />33.0 <br />31.5 <br />39.6 <br />11.1 <br />10.2 <br />6.2 <br />130 <br />36.5 <br />33.5 <br />20.5 <br />21.0 <br />36.6 <br />12.2 <br />11.1 <br />- 6.4 <br />120 <br />40.0 <br />36.5 <br />33.5 <br />30.5 <br />13.7 <br />* <br />12.3 <br />* <br />6.7 <br />7'0 <br />110 <br />100 <br />45.0 <br />* <br />403 <br />* <br />22.0 <br />23.0 <br />23.5 <br />29.0 <br />* Design vehicle requires a larger ICD (inscribed circle diameter) <br />Page 24 <br />