Laserfiche WebLink
TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2) <br />STEP 3 — CALCULATE TURN LANE DEMAND <br />Deceleration Based on speed and facility type determine deceleration length for turn lane. Deceleration Distance <br />Length 0 Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway <br />Page B-11 a Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways feet <br />Interpolation between values in the tables may be necessary based on speed data. <br />Storage Length ! Unsignalized Intersections Storage <br />Page B-12 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance <br />%, or equation on Page B-12. <br />Right Turn Lane — assumed to be 0 feet since in virtually all cases these vehicles would <br />have the right-of-way entering the intersection and would incur no delay <br />Signalized Intersections <br />❑ Synchro Output Available: 95th percentile queue length. <br />❑ Method 1 — Basic Equation: equation on Page B-13. 14­�> <br />❑ Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of feet <br />Critical Movement Calculations (see Page 4 of checklist) <br />Turn Lane Turn Lane Demand <br />Demand Add the Deceleration Distance and the Storage Distance <br />1 0� feet <br />STEP 4 — CALCULATE TURN LANE DESIGN <br />Determine Determine Taper based on Facility Type <br />Taper Taper Length <br />Page 8-1 7 ❑ Unconstrained Conventional/Expressway = 180 feet (1:15 taper) <br />❑ Constrained Expressway = 100 feet (1:8 taper) <br />[Constrained Conventional = 60 feet (1:5 taper) feet <br />Full Turn Lane <br />Take the Turn Lane Demand minus Taper Length <br />Full Width Turn Lane <br />Length (before <br />Length (no adjustments) <br />adjustments) <br />^a <br />feet <br />ADJUSTMENTS AND FINAL TURN LANE DESIGN <br />Adjust Taper <br />If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) <br />Adjusted Taper Length <br />Page B-21 <br />feet <br />Adjust Full turn <br />If grade is greater than 3% adjust based on Table B-9 (multiply the <br />+ <br />Lane Length <br />Deceleration Distance by adjustment in table and document the <br />difference in deceleration to the right. Page 8-19 ft <br />If heavy commercial is greater than averages shown in Table B-10, <br />increase Deceleration Distance by 30% and document the difference + <br />in length to the right. Page B-20 <br />Full Width Turn Lane <br />Are there more than 300 vehicles per hour? May consider dual lefts. <br />Length <br />The storage length required would be half of the calculated Storage <br />(with adjustments) <br />Distance. Document the difference in distance to the right. Page B-22 _ ft <br />Are there constraints with the adjacent intersections or driveways? <br />�� feet <br />Does the through lane queue extend further than the turn lane length. i <br />Document a review of the potential impact to the desired turn lane ft <br />length and adjust accordingly. Page 8-23 d 8-241 <br />orai Adjustments + ! - <br />ft <br />Development of Turn Lane Design Guidelines <br />