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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) <br />STEP 3 — CALCULATE TURN LANE DEMAND <br />Deceleration Based on speed and facility type determine deceleration length for turn lane. <br />Length <br />Deceleration Distance <br />g <br />Table B 1 for low seed (20 50 mph) Urban Conventional Roadway <br />p <br />Page 8-11 <br />Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways <br />.-feet <br />�^ <br />Interpolation between values in the tables may be necessary based on speed data. <br />Storage Length <br />Unsignalized Intersections <br />Storage <br />Page B-12 <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 />i <br />{ <br />i <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 />feet <br />❑ Method 2 — Look Up Tables: Tables 8 4 through B 6 on Page B-14 using Sum of <br />Critical Movement Calculations see Page 4 of checklist <br />Turn Lane <br />Turn Lane Demand <br />Demand <br />Add the Deceleration Distance and the Storage Distance <br />= a! ¢ feet <br />STEP 4 — CALCULATE TURN LANE DESIGN <br />Determine <br />Determine Taper based on Facility Type <br />Taper <br />Taper Length <br />❑ Unconstrained Conventional/Expressway = 180 feet (1:15 taper) <br />Pager r <br />❑ Constrained Expressway = 100 feet (1:8 taper) <br />i <br />`Constrained Conventional = 60 feet (1:5 taper) <br />feet <br />Full Turn Lane <br />_ __ _ <br />Take the Turn Lane Demand minus Taper Length <br />_ I <br />Full Width Turn Lane <br />Length (before <br />Length (no adjustments) <br />adjustments) <br />.. <br />feet <br />... __... ........... <br />1 <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-21 <br />(4 U feet <br />Adjust Full turn <br />If grade is greater than 3% adjust based on Table B-9 (multiply the + i <br />Lane Length <br />Deceleration Distance by adjustment in table and document the <br />difference in deceleration to the right. Page B-19 ft <br />........ -- <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 B-20 ft <br />Full Width Turn Lane <br />I <br />Are there more than 300 vehicles per hour? May consider dual lefts. <br />Length <br />IIII <br />The storage length required would be half of the calculated Storage <br />(with adjustments) <br />i Distance. Document the difference in distance to the right. Page 8-22 ft <br />Are there constraints with the adjacent intersections or driveways? <br />4 feet <br />Does the through lane queue extend further than the turn lane length? + I _ <br />Document a review of the potential impact to the desired turn lane ft <br />length and adjust accordingly. Page B-23 & B-24 <br />Total -Adjustments r ! - <br />Development of Turn Lane Design Guidelines <br />