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OCR for page 93
93 APPENDIX G Left-Turn Lane Added Between the Through Lanes of a Two-Way Highway ARIZONA ately begins. Reverse curves with a radius of 150 ft for speeds of 40 mph or less and 300 ft for speeds of 45 mph or more The median is widened until the full width of the turn lane are used to form the left-turn lane taper. becomes available and then a gap without a lane line is installed between the end of the shifting taper and the begin- ning of the storage area for the turn lane. This gap is 60 ft if LOUISIANA the posted or design speed is less than 40 mph, 90 ft if the posted or design speed is 40 to 50 mph, and 140 ft if the posted Reverse curves are used to transition from a two-lane section or design speed is more than 50 mph. to a three-lane section of roadway. A reverse curve is also used for the taper for the left-turn lane, which begins after the three-lane section is fully formed. A reverse curve is also ARKANSAS used to transition from a three-lane section back to a two-lane section of roadway on the departure side of the intersection. The median is widened only for the first two-thirds of the shift- Dimensions are not specified. ing taper for the through lane, after which the painted median begins to narrow again to form the left-turn lane. Thus, the last one-third of the shifting taper for the through lane is also used MICHIGAN as the taper for drivers moving into the left-turn lane. The median is widened until the full width of the turn lane becomes available and then a gap without a lane line is CALIFORNIA installed between the end of the shifting taper and the begin- ning of the solid lane line that separates the left-turn lane The median is widened until the full width of the turn lane from the adjacent through lane. The gap is at least 75 ft long. becomes available and then a left-turn lane taper immediately begins. The left-turn lane taper is 60 or 90 ft in business, res- idential, or urban areas and 120 ft in high-speed rural areas. MISSOURI The length of the shifting taper for the through lane is cal- The median is widened until the full width of the turn lane culated using W S for speeds of 45 mph or more and using becomes available and then a left-turn lane taper immedi- WS2/60 for speeds of 40 mph or less, where S is the off-peak ately begins. The length of the left-turn lane taper is approx- 85th percentile speed. However, in urban areas where space imately 100 ft. is restricted, S may be reduced by 10 or 20 mph. MONTANA IDAHO The median is widened until the full width of the turn lane The median is widened for the first half of the shifting taper, becomes available and then a left-turn lane taper immediately and then a reverse curve left-turn lane taper begins. The dis- begins. The length of the left-turn lane taper is calculated tance in feet from the halfway point in the shifting taper to from a taper rate based on design speed and is shown in the the beginning of the full-width left-turn lane is five times the same chart. The left-turn lane taper rate varies from 8-to-1 for speed limit in mph. 20 mph (shown as 30 km/h) to 18-to-1 for 70 mph (shown as 120 km/h). IOWA The length of the shifting taper for the through lane is Reverse curves with radii of 12,000 ft are used to transition calculated from a taper rate based on design speed and is from a two-lane to a three-lane section of roadway. A ten-to- shown in a chart. The shifting taper rate varies from 10-to-1 one taper for the left-turn lane begins after the three-lane sec- for 20 mph (shown as 30 km/h) to 75-to-1 for 70 mph (shown tion is fully formed. as 120 km/h). KANSAS NEW HAMPSHIRE The median is widened until the full width of the turn lane The median is widened until the full width of the turn lane becomes available and then a left-turn lane taper immedi- becomes available and then a left-turn lane taper immediately

OCR for page 93
94 begins. The length of the left-turn lane taper is 75 ft if the TEXAS posted speed limit is 40 mph or less and is 100 ft if the posted speed limit is 45 mph or more. The median is widened until the full width of the turn lane becomes available. A left-turn lane taper begins an unspeci- fied distance downstream from the point where the full width OHIO of the turn lane becomes available. The length of the left-turn lane taper is unspecified. The median is widened until the full width of the turn lane be- comes available. A left-turn lane taper begins 100 ft down- stream of the point where the full width of the turn lane be- UTAH comes available. The length of the left-turn lane taper is 50 ft. The median is widened using half the normal distance of L until the full width of the turn lane becomes available. A left- OREGON turn lane taper begins 20 ft downstream from the point where the full width of the turn lane becomes available. The length The median is widened until the full width of the turn lane of the left-turn lane taper is unspecified. becomes available. Two methods of marking the left-turn lane may be used. A set of reverse curves may be used with the reverse curves starting at the point where the full three- WASHINGTON lane width becomes available (the length of the reverse curves is given in a data table and varies from 98 to 180 ft for 35 to The median is widened using a shifting taper of L = WS (even 65 mph design speeds). A second option that uses the same for low speeds) until the full width of the turn lane becomes length as the reverse curves is to extend the double yellow available. A left-turn lane taper begins at the point where the centerline on the left-hand side of the approach through lane full width of the turn lane becomes available. The length of the for one-eighth of the length and then leave a gap in the pave- left-turn taper is based on the posted speed limit and is given ment markings until the solid lane line separating the left- in a table. The length of the left-turn taper varies from 75 ft for turn lane from the through lane begins (the only longitudinal a 25 mph speed limit to 180 ft for a 60 mph speed limit. pavement marking in the gap area is the centerline adjacent to the departure lane in the opposite direction). WYOMING The length of the shifting taper for the through lane is cal- The median is widened until the full width of the turn lane culated using W S for speeds of 35 mph or more. becomes available and then a 150-ft left-turn lane taper immediately begins. PENNSYLVANIA TUCSON/PIMA COUNTY, AZ The median is widened until the full width of the turn lane becomes available. A left-turn lane taper begins a distance that The median is widened until the full width of the turn lane is half as long as the shifting taper downstream of the point becomes available and then a gap without a lane line is where the full width of the turn lane becomes available. The installed between the end of the shifting taper and the begin- length of the left-turn lane taper is one-sixth the length of the ning of the storage area for the turn lane. This gap is 60 ft if shifting taper. the posted speed limit is 35 mph or less, 90 ft if the posted speed limit is 40 or 45 mph, and 120 ft if the posted speed limit is 50 mph or more. SOUTH DAKOTA The median is widened until two-thirds of the width of the turn No standards were found for: lane becomes available. A left-turn lane taper begins at the Alabama Maryland Rhode Island point where two-thirds of the width of the turn lane becomes Alaska Massachusetts South Carolina available. The length of the left-turn lane taper is unspecified. Colorado Minnesota Vermont Connecticut Mississippi Virginia Delaware Nebraska West Virginia TENNESSEE Florida Nevada Wisconsin Georgia New Jersey District of Columbia The median is widened until three-fourths of the width of the Hawaii New Mexico Puerto Rico turn lane becomes available. A left-turn lane taper begins at Illinois New York Charlotte, NC the point where three-fourths of the width of the turn lane Indiana North Carolina Los Angeles, CA becomes available. The length of the left-turn lane taper is Kentucky North Dakota New York, NY unspecified. Maine Oklahoma