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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) <br />STEP 3 - CALCULATE TURN LANE DEMAND <br />Deceleration <br />Based on speed and facility type determine deceleration length for turn lane. <br />Deceleration Distance <br />Length <br />Table B-1 for low speed (20 - 50 mph) Urban Conventional Roadway <br />Page 3-1 f <br />. Table B-2 for high speed (45 - 75 mph) Rural and Urban Roadways <br />4(oc3 feet <br />Interpolation between values in the tables may be necessary based on speed data. <br />Storage Length <br />Unsignalized Intersections <br />Storage <br />Page 8-i2 <br />Left Turn Lane - see Table B-3, based on Left -Turning Volume and Heavy Commercial <br />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 />L <br />feet <br />❑ Method 2 - Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of <br />Critical Movement Calculations fsee_Flage 4 of checklist) <br />Turn Lane <br />Turn Lane Demand <br />Demand <br />Add the Deceleration Distance and the Storage Distance <br />feet <br />STEP 4 - CALCULATE TURN LANE DESIGN <br />Determine <br />Determine Taper based on Facility Type <br />Taper <br />Taper Length <br />ElUnconstrained Conventional/Expressway = 180 feet (1:15 taper) <br />Page e-, <br />❑ Constrained Expressway = 100 feet (1:8 taper) <br />❑ Constrained Conventional = 60 feet (1:5 taper) <br />? feet <br />Full Turn Lane <br />Take the Turn Lane Demand minus Taper Length <br />Full Width Turn Lane <br />Length (before <br />Length (no adjustments) <br />adjustments) <br />r feet <br />c <br />ADJUSTMENTS AND FINAL TURN LANE DESIGN <br />Adjust Taper <br />If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) <br />Adjusted Taper Length <br />Page B-2-f <br />feet <br />Adjust Full turn <br />If grade is greater than 3% adjust based on Table B-9 (multiply the <br />+ <br />Lane Length <br />Deceleration Distance by adjustment in table and document the <br />difference in deceleration to the right. page 3• f9 ft <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 />Full Width Turn Lane <br />Are there more than 300 vehicles per hour? May consider dual lefts. <br />Length <br />The storage length required would be half of the calculated Storage <br />(with adjustments) <br />Distance. Document the difference in distance to the right. Page 3-22 ft <br />4 <br />Are there constraints with the adjacent intersections or driveways? + / <br />feet <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 />I°atai Adjustments + l - <br />ft <br />Development of Turn Lane Design Guidelines <br />