2017.04.17 CC Packet - Laserfiche WebLink

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Deceleration Length Page 8-11 Storage Length Page 8-12 Turn Lane Demand Determine Taper Page 8-17 Full Turn Lane Length (before adjustments) TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) STEP 3 — CALCULATE TURN LANE DEMAND Based on speed and facility type determine deceleration length for turn lane. • Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway • Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways Interpolation between values in the tables may be necessary based on speed data. Unsignalized Intersections Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial %, 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. ❑ Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of Critical Movement Calculations (see Page 4 of checklist) Add the Deceleration Distance and the Storage Distance STEP 4 — CALCULATE TURN LANE DESIGN Determine Taper based on Facility Type ❑ Unconstrained Conventional/Expressway = 180 feet (1:15 taper) ❑ Constrained Expressway = 100 feet (1:8 taper) ,JiC Constrained Conventional = 60 feet (1:5 taper) Take the Turn Lane Demand minus Taper Length T 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 B-21 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 8-19 _ .W 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 k Are there more than 300 vehicles per hour? May consider dual lefts. The storage length required would be half of the calculated Storage Distance. Document the difference in distance to the right. Page 8-22 ft Are there constraints with the adjacent intersections or driveways? Does the through lane queue extend further than the turn lane length? + l - Document a review of the potential impact to the desired turn lane ft length and adjust accordingly. Page 3-23 & B-24 Total Adjustinents Deceleration Distance 14 Q feet Storage Distance feet I _ __ Turn Lane Demand = E 0 feet Taper Length feet Full Width Turn Lane Length (no adjustments) feet Adjusted Taper Length feet Full Width Turn Lane Length (with adjustments) 4 ft I _. feet Development of Turn Lane Design Guidelines