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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) STEP 3 - CALCULATE TURN LANE DEMAND Deceleration Based on speed and facility type determine deceleration length for turn lane. Deceleration Distance I Length 0 Table B-1 for low speed (20 - 50 mph) Urban Conventional Roadway Page 3- I l 0 Table B-2 for high speed (45 - 75 mph) Rural and Urban Roadways feet Interpolation between values in the tables may be necessary based on speed data. Storage Length Unsignalized Intersections Storage Page B-12 Left Turn Lane - see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance %, or equation on Page B-12. Right Turn Lane - assumed to be 0 feet since in virtually all cases these vehicles would have the right-of-way entering the intersection and would incur no delay Signalized Intersections ❑ Synchro Output Available: 95th percentile queue length. ❑ Method 1 - Basic Equation: equation on Page B-13_ El Method 2 - Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of feet Critical Movement Calculations [see_Page 4 of checklist) Turn Lane Turn Lane Demand Demand Add the Deceleration Distance and the Storage Distance _ _ feet STEP 4 - CALCULATE TURN LANE DESIGN Determine Determine Taper based on Facility Type Taper Taper Length ❑ Unconstrained Conventional/Expressway = 180 feet (1:15 taper) Page 3-17 ❑ Constrained Expressway = 100 feet (1:8 taper) i i ❑ Constrained Conventional = 60 feet (1:5 taper) feet Full Turn Lane Take the Turn Lane Demand minus Taper Length Full Width Turn Lane Length (before Length (no adjustments) adjustments) I 43 feet I ADJUSTMENTS AND FINAL TURN LANE DESIGN Adjust Taper If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) Adjusted Taper Length Page 3-21 feet Adjust Full turn If grade is greater than 3% adjust based on Table B-9 (multiply the + / - Lane Length Deceleration Distance by adjustment in table and document the difference in deceleration to the right. P-�ye .3-19, ft If heavy commercial is greater than averages shown in Table B-10, increase Deceleration Distance by 30% and document the difference + in length to the right. Page 3-20 ft Full Width Turn Lane Are there more than 300 vehicles per hour? May consider dual lefts. Length The storage length required would be half of the calculated Storage (with adjustments) Distance. Document the difference in distance to the right. Page 3-22 ft Are there constraints with the adjacent intersections or driveways?feet Does the through lane queue extend further than the turn lane length? + / - Document a review of the potential impact to the desired turn lane ft length and adjust accordingly. Page 3-23 &� 3-2¢ Torai Adjustments - + / - ft Development of Turn Lane Design Guidelines