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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 Length 0 Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway Page B-11 . Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways & 10 feet kInterpolation between values in the tables may be necessary based on speed data. Storage Length I Unsignalized Intersections Storage � Page B-12 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance I I 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 ElSynchro Output Available: 95th percentile queue length. ❑ Method 1 — Basic Equation: equation on Page B-13. t.5 3 feet ❑ Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of _ Critical Movement Calculations see Pa e 4 of checklist f Turn Lane Turn Lane Demand Demand Add the Deceleration Distance and the Storage Distance _i 0 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 8-1, i ❑ Constrained Ex resswa = 100 feet 1:8 taper) p Y ( P ❑ 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) j feet _1.2I i { ADJUSTMENTS AND FINAL TURN LANE DESIGN 4 Adjust Taper If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) Adjusted Taper Length Page B-21 . --- feet 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 B-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 B-20 ! ft Full Width Turn Lane Are there more than 300 vehicles per hour? May consider dual lefts. Length i 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? + / r 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 B-23 <& 8-24 j rotai Adjustments + I - i ft Development of Turn Lane Design Guidelines