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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 0 Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway i Page B-11 . 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. j Storage Length Unsignalized Intersections Storage Page B-12 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance II or equation on Page B-12. ` Right Turn Lane — assumed to be 0 feet since in virtually all cases these vehicles would i 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. ❑ Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of I Critical Movement Calculations see Page 4 of Checklist . Turn Lane Demand Add the Deceleration Distance and the Storage Distance STEP 4 — CALCULATE TURN LANE DESIGN Determine Determine Taper based on Facility Type Taper Page B-17 ElUnconstrained Conventional/Expressway = 180 feet (1:15 taper) I I Full Turn Lane Length (before adjustments) ❑ Constrained Expressway = 100 feet (1:8 taper) [Constrained Conventional = 60 feet (1:5 taper) i Take the Turn Lane Demand minus Taper Length 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) Page 8-21 Adjust Full turn If grade is greater than 3% adjust based on Table B-9 (multiply the I Lane Length Deceleration Distance by adjustment in table and document the + / difference in deceleration to the right. Page 8-19 ft feet Turn Lane Demand # Q, feet Taper Length feet I Full Width Turn Lane Length (no adjustments) j feet Adjusted Taper Length 0 feet 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 B•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 B-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 8-23 d 8-241 i Tcral Adjustments I +I- ft Development of Turn Lane Design Guidelines