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14 Type of Lane Line Between Dual Turn Lanes MD, MI, NV, NC, TN, TUC--entire length of full-width and Adjacent Through Lane (11 agencies) turn lanes LAN--from the stop line to the midpoint between the Except for one agency, the design standards consistently show upstream end of the full-width turn lanes and the a solid lane line between the dual turn lanes and the adjacent upstream end of the turn lane taper. through lane. The design standards for Maryland state that the solid lane LANE LINE EXTENSIONS INTO INTERSECTION line between the turn lanes and the adjacent through lane FOR DUAL TURN LANES starts at the stop line and ends at the halfway point of the full- width turn lanes. A dotted line (3-ft segments with 9-ft gaps) Figure 5 shows an example of a lane line extension into an is used from the halfway point to the upstream end of the full- intersection for dual turn lanes. width turn lanes. 2003 MUTCD Provisions Width of Lane Line Between Dual Turn Lanes and Adjacent Through Lane (7 agencies) The MUTCD recommends that dotted or solid line markings be used to extend the lane line between dual turn lanes The following widths are explicitly specified in the design through an intersection. Figure 3B-11 shows a solid line standards for the lane line between dual turn lanes and the being used to extend the lane line between dual turn lanes adjacent through lane: through the intersection. Figure 3B-22 shows a white dotted line being used to extend the lane line between dual turn MI, TN--4 in. lanes through the intersection and a single yellow dotted line NC--4 or 6 in. being used to extend the double yellow centerline to the left CO, FL, NV, TUC--8 in. of dual left-turn lanes through the intersection. The notes in both of these figures mention that the lane line extensions may be dotted or solid lines (see Appendix A for figures). Length of Lane Line Between Dual Turn Lanes and Adjacent Through Lane (7 agencies) Item E in Paragraph 1 of Section 3A.05 contains the fol- The following lengths are explicitly specified in the design lowing standards: "A dotted line shall consist of noticeably standards for the lane line between dual turn lanes and the shorter line segments separated by shorter gaps than used for adjacent through lane: a broken line. The width of a dotted line shall be at least the Point where full shadowing first becomes available Left-turn Shifting taper taper (a) Widening on one side only Point where full shadowing first becomes available Shifting taper Left-turn taper (b) Symmetrical widening on both sides FIGURE 5 Examples of left-turn lanes added between through lanes of two-lane highways.
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15 same as the width of the line it extends." Even though these from the stop line to the edge line extended of the cross street provisions are classified as requirements, they do not specify is a solid line. the width or the pattern of dotted lines, which varies signifi- cantly among the policies of the various agencies. The design standards for Idaho note that when the volume of turning vehicles exceeds 200 per hour, a solid line is used Paragraph 3 of Section 3A.05 contains the following (instead of a dotted line) for the extension through the inter- option: "A dotted line for line extensions may consist of 2 ft section of the lane line between the two turn lanes. line segments and 2 ft to 6 ft gaps." The design standards for Oregon state that the lane line Paragraphs 1 and 2 of Section 3B.08 contain the follow- between the two turn lanes may be extended through the ing standard and option: "Pavement markings extended into intersection using a dotted or solid line. The dotted or solid or continued through an intersection or interchange area shall line may be continued through a marked crosswalk. be the same color and at least the same width as the line markings they extend, except that a normal line may be used The design standards for Wyoming state that the lane line to extend a wide line through an intersection." This standard between the two turn lanes is typically extended through the specifies the color, but does not specify the use or pattern of intersection using a dotted or solid line. pavement marking extensions and gives flexibility as to the width. Pattern of Dotted Lines (26 agencies) Paragraphs 3 and 5 of Section 3B.08 contain the follow- ing guidance: "Where highway design or reduced visibility The following patterns are used for dotted lines that extend the conditions make it desirable to provide control or to guide lane line between the two turn lanes through an intersection: vehicles through an intersection or interchange, such as at offset, skewed, complex, or multilegged intersections, on WV--0.5-ft segments with 2-ft gaps curved roadways, or where multiple turn lanes are used, dot- CA--1-ft segments with 6-ft gaps ted line markings should be used to extend longitudinal line LAN--1-ft segments with 8-ft gaps markings through an intersection or interchange area. Where CO, FL, HI, ID, KS, MI, NY, PA, RI, TN, VA, DC, greater restriction is required, solid lane lines or channeliz- CLT--2-ft segments with 4-ft gaps ing lines should be extended into or continued through inter- IN--typically 2-ft segments with 4-ft or longer gaps, with sections or major driveways." a segment-to-gap ratio of no greater than 1 to 4 SC--2-ft segments with 5-ft gaps Paragraph 6 of Section 3B.08 contains the following guid- NH, OR, WA, WY, TUC--2-ft segments with 6-ft gaps ance: "A single line of equal width to one of the lines of the MT--typically 2-ft segments with 8-ft gaps double line should be used to extend a double line through an NC--2-ft segments with 8- or 13-ft gaps intersection." MD--3-ft segments with 9-ft gaps. Width of Dotted Lines (7 agencies) Use Versus Non-Use of Dotted Lines (23 agencies) The design standards for 13 agencies (CA, IN, MD, MT, NH, The following widths are explicitly specified in the design NY, OR, PA, SC, WV, DC, CLT, and LAN) state that the use standards for dotted lines that extend the lane line between of a dotted line to extend the lane line between the two turn the two turn lanes through an intersection: lanes through the intersection is optional. CA, HI, NY, WV, DC, TUC--4 in. TN--8 in. The design standards for Tennessee and Wyoming note that a dotted line is typically used to extend the lane line between the two turn lanes through the intersection. Other Considerations Regarding Lane Line Extensions for Dual Turn Lanes (4 agencies) The design standards for eight agencies (CO, FL, ID, NC, RI, VA, WA, and TUC) state that the use of a dotted line to The design standards for Colorado require that the lane line extend the lane line between the two turn lanes through the separating the right-most left-turn lane from the adjacent intersection is required. through lane be extended into the intersection just far enough to allow left-turning vehicles in opposite directions to miss The design standards for Colorado state that the lane line each other by at least 4 ft. between the two turn lanes is extended through the intersec- tion using either a dotted or solid line. When dotted lane line The design standards for Florida state that the centerline or extensions are used, the portion of the lane line extension edge line on the left-hand side or the lane line on the right-hand