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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) STEP 3 — CALCULATE TURN LANE DEMAND I Deceleration Based on speed and facility type determine deceleration length for turn lane. Deceleration Distance ° Length . Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway Page B-11 0 Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways /G 0 feet Interpolation between values in the tables may be necessary based on speed data. Storage Length •" Unsignalized Intersections Storage Page 8-12 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance k %, or equation on Page B-12. i 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 E Signalized Intersections ❑ Synchro Output Available: 95th percentile queue length. _ 11 ❑ Method 1 — Basic Equation: equation on Page B-13. feet El Method 2 — Look Up Tables: Tables B-4 through B 6 on Page B-14 using Sum of � Critical Movement Calculations (see Poeg 4 of checklist) Turn n Lane Turn Lane Demand Demand Add the Deceleration Distance and the Storage Distance _ 0 feet STEP 4 — CALCULATE TURN LANE DESIGN Determine Determine Taper based on Facility Type � Taper Taper Length Pager r ❑ Unconstrained Conventional/Expressway = 180 feet (1:15 taper) ❑ Constrained Expressway = 100 feet (1:8 taper) I 'Constrained Conventional = 60 feet (1:5 taper) 00 feet i i Full Turn Lane Take the Turn Lane Demand minus Taper Length Full Width Turn Lane Length (before Length (no adjustments) adjustments) feet --- ADJUSTMENTS AND FINAL TURN LANE DESIGN T ^T Adjust Taper If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) Adjusted Taper Length Page 8.21 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. page 9-19 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 8-20 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 8-22 �..._ ft Are there constraints with the adjacent intersections or driveways? /5 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. Paye 3-23 & 8-24 Total Adfuslrnenis -- - + l - ft Development of Turn Lane Design Guidelines