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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) <br />STEP 3 — CALCULATE TURN LANE DEMAND i <br />Deceleration Based on speed and facility type determine deceleration length for turn lane. Deceleration Distance <br />Length 0 Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway <br />Page 3-1 f . Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways feet <br />I Interpolation between values in the tables may be necessary based on speed data. <br />I •- <br />Storage Length Unsignalized Intersections Storage <br />Page 8-i2 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance <br />or equation on Page B-12. <br />Right Turn Lane — assumed to be 0 feet since in virtually all cases these vehicles would <br />have the right-of-way entering the intersection and would incur no delay <br />Signalized Intersections <br />❑ Synchro Output Available: 95th percentile queue length. <br />❑ Method 1 — Basic Equation: equation on Page B-13. <br />❑ Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of <br />Critical Movement Calculations see Page 4 of checklist _ <br />Turn Lane m <br />Demand Add the Deceleration Distance and the Storage Distance <br />I <br />STEP 4 — CALCULATE TURN LANE DESIGN <br />Determine Determine Taper based on Facility Type <br />Taper <br />Page e-, ElUnconstrained Conventional/Expressway = 180 feet (1:15 taper) <br />❑ Constrained Expressway = 100 feet (1:8 taper) <br />❑ Constrained Conventional = 60 feet (1:5 taper) <br />I Full Turn Lane Take the Turn Lane Demand minus Taper Length <br />Length (before <br />adjustments) <br />i <br />Adjust Taper <br />Page B-2•f <br />ADJUSTMENTS AND FINAL TURN LANE DESIGN <br />If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) <br />Adjust Full turn If grade is greater than 3% adjust based on Table B-9 (multiply the <br />Lane Length Deceleration Distance by adjustment in table and document the <br />difference in deceleration to the right, page a• f9 <br />If heavy commercial is greater than averages shown in Table B-10, , <br />increase Deceleration Distance by 30% and document the difference <br />in length to the right. page 3-20 <br />Are there more than 300 vehicles per hour? May consider dual lefts. <br />The storage length required would be half of the calculated Storage <br />Distance. Document the difference in distance to the right. Page 3-22 <br />Are there constraints with the adjacent intersections or driveways? <br />Does the through lane queue extend further than the turn lane length? <br />Document a review of the potential impact to the desired turn lane <br />length and adjust accordingly. page 8-2 3 t s-24 <br />Tonal Adjustments <br />ft <br />feet i <br />Turn Lane Demand <br />feet <br />3 <br />Taper Length <br />i <br />feet <br />Full Width Turn Lane <br />Length (no adjustments) <br />i <br />I' feet <br />Adjusted Taper Length ' <br />feet <br />ft Full Width Turn Lane <br />Length <br />(with adjustments) <br />ft <br />feet <br />ft <br />ft <br />Development of Turn Lane Design Guidelines <br />