National Academies Press: OpenBook

Pavement Markings--Design and Typical Layout Details (2006)

Chapter: Appendix G - Left-Turn Lane Added Between the Through Lanes of a Two-Way Highway

« Previous: Appendix F - Dotted Lines in Turn Lane Tapers
Page 93
Suggested Citation:"Appendix G - Left-Turn Lane Added Between the Through Lanes of a Two-Way Highway." National Academies of Sciences, Engineering, and Medicine. 2006. Pavement Markings--Design and Typical Layout Details. Washington, DC: The National Academies Press. doi: 10.17226/13947.
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Page 93
Page 94
Suggested Citation:"Appendix G - Left-Turn Lane Added Between the Through Lanes of a Two-Way Highway." National Academies of Sciences, Engineering, and Medicine. 2006. Pavement Markings--Design and Typical Layout Details. Washington, DC: The National Academies Press. doi: 10.17226/13947.
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Page 94

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93 ARIZONA The median is widened until the full width of the turn lane 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 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 or design speed is more than 50 mph. ARKANSAS The median is widened only for the first two-thirds of the shift- 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 as the taper for drivers moving into the left-turn lane. CALIFORNIA The median is widened until the full width of the turn lane 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. The length of the shifting taper for the through lane is cal- culated using W × S for speeds of 45 mph or more and using WS2/60 for speeds of 40 mph or less, where S is the off-peak 85th percentile speed. However, in urban areas where space is restricted, S may be reduced by 10 or 20 mph. IDAHO The median is widened for the first half of the shifting taper, and then a reverse curve left-turn lane taper begins. The dis- tance in feet from the halfway point in the shifting taper to the beginning of the full-width left-turn lane is five times the speed limit in mph. IOWA Reverse curves with radii of 12,000 ft are used to transition from a two-lane to a three-lane section of roadway. A ten-to- one taper for the left-turn lane begins after the three-lane sec- tion is fully formed. KANSAS The median is widened until the full width of the turn lane becomes available and then a left-turn lane taper immedi- 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 are used to form the left-turn lane taper. LOUISIANA Reverse curves are used to transition from a two-lane section 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 used to transition from a three-lane section back to a two-lane section of roadway on the departure side of the intersection. Dimensions are not specified. MICHIGAN The median is widened until the full width of the turn lane 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 solid lane line that separates the left-turn lane from the adjacent through lane. The gap is at least 75 ft long. MISSOURI The median is widened until the full width of the turn lane becomes available and then a left-turn lane taper immedi- ately begins. The length of the left-turn lane taper is approx- imately 100 ft. MONTANA The median is widened until the full width of the turn lane becomes available and then a left-turn lane taper immediately begins. The length of the left-turn lane taper is calculated from a taper rate based on design speed and is shown in the same chart. The left-turn lane taper rate varies from 8-to-1 for 20 mph (shown as 30 km/h) to 18-to-1 for 70 mph (shown as 120 km/h). The length of the shifting taper for the through lane is calculated from a taper rate based on design speed and is shown in a chart. The shifting taper rate varies from 10-to-1 for 20 mph (shown as 30 km/h) to 75-to-1 for 70 mph (shown as 120 km/h). NEW HAMPSHIRE The median is widened until the full width of the turn lane becomes available and then a left-turn lane taper immediately APPENDIX G Left-Turn Lane Added Between the Through Lanes of a Two-Way Highway

begins. The length of the left-turn lane taper is 75 ft if the posted speed limit is 40 mph or less and is 100 ft if the posted speed limit is 45 mph or more. OHIO 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- comes available. The length of the left-turn lane taper is 50 ft. OREGON The median is widened until the full width of the turn lane 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- 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 65 mph design speeds). A second option that uses the same length as the reverse curves is to extend the double yellow centerline on the left-hand side of the approach through lane for one-eighth of the length and then leave a gap in the pave- ment markings until the solid lane line separating the left- turn lane from the through lane begins (the only longitudinal pavement marking in the gap area is the centerline adjacent to the departure lane in the opposite direction). The length of the shifting taper for the through lane is cal- culated using W × S for speeds of 35 mph or more. PENNSYLVANIA The median is widened until the full width of the turn lane becomes available. A left-turn lane taper begins a distance that is half as long as the shifting taper downstream of the point where the full width of the turn lane becomes available. The length of the left-turn lane taper is one-sixth the length of the shifting taper. SOUTH DAKOTA The median is widened until two-thirds of the width of the turn lane becomes available. A left-turn lane taper begins at the point where two-thirds of the width of the turn lane becomes available. The length of the left-turn lane taper is unspecified. TENNESSEE The median is widened until three-fourths of the width of the turn lane becomes available. A left-turn lane taper begins at the point where three-fourths of the width of the turn lane becomes available. The length of the left-turn lane taper is unspecified. 94 TEXAS 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 of the turn lane becomes available. The length of the left-turn lane taper is unspecified. UTAH The median is widened using half the normal distance of L until the full width of the turn lane becomes available. A left- turn lane taper begins 20 ft downstream from the point where the full width of the turn lane becomes available. The length of the left-turn lane taper is unspecified. WASHINGTON The median is widened using a shifting taper of L = WS (even for low speeds) until the full width of the turn lane becomes available. A left-turn lane taper begins at the point where the full width of the turn lane becomes available. The length of the left-turn taper is based on the posted speed limit and is given in a table. The length of the left-turn taper varies from 75 ft for a 25 mph speed limit to 180 ft for a 60 mph speed limit. WYOMING The median is widened until the full width of the turn lane becomes available and then a 150-ft left-turn lane taper immediately begins. TUCSON/PIMA COUNTY, AZ The median is widened until the full width of the turn lane 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 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. No standards were found for: Alabama Alaska Colorado Connecticut Delaware Florida Georgia Hawaii Illinois Indiana Kentucky Maine Maryland Massachusetts Minnesota Mississippi Nebraska Nevada New Jersey New Mexico New York North Carolina North Dakota Oklahoma Rhode Island South Carolina Vermont Virginia West Virginia Wisconsin District of Columbia Puerto Rico Charlotte, NC Los Angeles, CA New York, NY

Next: Appendix H - Solid Lane Lines Between Through Lanes on Signalized Approaches »
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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 356: Pavement Markings—Design and Typical Layout Details identifies variations in pavement marking designs, practices, and policies, as provided by 48 of 50 state departments of transportation, and transportation agencies from the District of Columbia, Puerto Rico and four cities.

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