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53 COMBINATIONS OF MEDIAN OPENINGS ALONG ARTERIAL STREETS Earlier in this chapter, seven categories of typical median openings were presented, along with subcategories based on the presence of left-turn lanes or loons or type of turning maneuvers permitted. Each type of typical median opening design represents one individual median opening. Often, high- way agencies use combinations of median opening designs to accomplish a particular goal along an arterial. This section presents several typical combinations of median opening designs that can be used along an arterial. Each combination is presented as a sum of the individual typical median opening designs that make up the combi- Figure 37. Vehicular conflicts at a conventional median nation. For example, the first combination (Combination opening at a four-leg intersection (27, 33). C1) is a directional midblock median opening with left-turn lanes (Type 2b) between two four-leg intersections with directional median openings that accommodate left turns opening designs should rank in the following order of rela- from the major road (Type 6a). Thus, this combination is tive safety: represented as: Midblock Median Openings Combination C1 = Type 6a + Type 2b + Type 6a 7--Midblock Jughandle 1--Conventional Midblock Median Opening Eight typical combinations of median opening designs are 2--Directional Midblock Median Opening presented below; many other combinations are possible. Chap- ter 6 of this report presents two examples of a safety com- Median Openings at Three-Leg Intersections parison between an individual median opening and a combi- nation of median openings accommodating the same turning 4--Directional Median Opening at Three-Leg Intersec- movements. tion 3--Conventional Median Opening at Three-Leg Inter- section Combination C1--Directional Midblock Median Opening Between Four-Leg Intersections With Median Openings at Four-Leg Intersections Directional Median Openings 6--Directional Median Opening at Four-Leg Intersection Combination C1 consists of a directional midblock median 5--Conventional Median Opening at Four-Leg Intersec- opening with left-turn lanes located between two four-leg inter- tion sections with left-turn lanes and directional median openings TABLE 15 Total number of conflict points for each typical median opening design Number of Typical median opening design conflict points 1. Conventional Midblock Median Opening 4 2. Directional Midblock Median Opening 4 3. Conventional Median Opening at Three-Leg 11 Intersection 4. Directional Median Opening at Three-Leg 6 Intersection 5. Conventional Median Opening at Four-Leg 32 Intersection 6. Directional Median Opening at Four-Leg 12 Intersection 7. Midblock Jughandle 3

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54 that accommodate U-turns and left turns from the major road, Combination C3--Directional Midblock Median but not left turns from the minor road. This combination is Opening Between Four-Leg Intersections With illustrated in Figure 38 and is represented as Conventional Median Openings Combination C3 includes a directional midblock median Combination C1 = Type 6a + Type 2b + Type 6a opening with left-turn lanes located between two four-leg intersections with left-turn lanes and conventional median Combination C1 can be used as an alternative to direct left openings. This combination is illustrated in Figure 40 and is turns in order to reduce conflicts and to improve safety along represented as an arterial. Midblock U-turns make it possible to prohibit left turns from the minor road at each four-leg intersection and Combination C3 = Type 5b + Type 2b + Type 5b from driveways along the arterial. Vehicles must make left- turn movements by turning right onto the arterial and then Combination C3 provides access to through vehicles on the making U-turns downstream. This combination is appropri- major road to development on the opposite side of the median. ate where left-turn demand on the minor road is relatively The directional midblock median opening can accommodate low or where it is desirable to reduce U-turn demand at the heavy U-turn volumes. This combination is appropriate downstream intersection. where left-turn demand on the minor road is relatively light or where it is desirable to reduce U-turn demand at the down- stream intersection. Combination C2--Conventional Midblock Median Opening Between Four-Leg Intersections With Conventional Combination C4--Directional Midblock Median Median Openings Opening Between Four-Leg Intersections Without Median Openings Combination C2 is a conventional midblock median open- ing with left-turn lanes located between two four-leg inter- Combination C4 is a directional midblock median opening sections with left-turn lanes and conventional median open- with left-turn lanes located between two four-leg intersec- ings. This combination is illustrated in Figure 39 and is tions without median openings. This combination is illus- represented as: trated in Figure 41 and is represented as Combination C2 = Type 5b + Type 1b + Type 5b Combination C4 = Closed Type 5a + Type 2b + Closed Type 5a Combination C2 provides access to through vehicles on the major road to development on the opposite side of the median. Combination C4 can be used as an alternative to direct left This combination is appropriate where left-turn demand on turns in order to reduce conflicts and to improve safety along the minor road is relatively high or where it is desirable to an arterial. Midblock U-turns make it possible to close the reduce U-turn demand at the downstream intersection. median opening at each four-leg intersection and prohibit Combination C1 = Type 6a + Type 2b + Type 6a Figure 38. Combination C1--directional midblock median opening between four-leg intersections with directional median openings.

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55 Combination C2 = Type 5b + Type 1b + Type 5b Figure 39. Combination C2--Conventional midblock median opening between four-leg intersections with conventional median openings. Combination C3 = Type 5b + Type 2b + Type 5b Figure 40. Combination C3--Directional midblock median opening between four-leg intersections with conventional median openings. Combination C4 = Closed Type 5a + Type 2b + Closed Type 5a Figure 41. Combination C4--directional midblock median opening between four-leg intersections without median openings.

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56 left-turn movements from driveways along the arterial. Vehi- tions without median openings. This combination is illustrated cles must make left-turn or crossing movements by turning in Figure 43 and is represented as right onto the arterial and then making U-turns downstream. The directional midblock median opening can accommodate Combination C6 = Closed Type 5a + Type 1b heavy U-turn volumes. This combination is appropriate where + Closed Type 5a conventional median openings at four-leg intersections are experiencing safety problems such that the most effective Combination C6 is similar to Combination C4, except that treatment is to close the median openings. Combination C6 has a conventional rather than a directional midblock median opening. Combination C6 serves the same Combination C5--Directional Midblock Median purposes as Combination C4, but is more appropriate where Opening Between Three-Leg Intersections U-turn volumes are relatively light. Without Median Openings Combination C5 includes a directional midblock median Combination C7--Conventional Midblock opening with left-turn lanes located between two three-leg Median Opening Between Three-Leg Intersections Without Median Openings intersections without median openings. This combination is illustrated in Figure 42 and is represented as Combination C7 consists of a conventional midblock median opening with left-turn lanes between two three-leg Combination C5 = Closed Type 3a + Type 2b intersections without median openings. This combination is + Closed Type 3a illustrated in Figure 44 and is represented as Combination C5 can be used as an alternative to direct left Combination C7 = Closed Type 3a + Type 1b turns in order to reduce conflicts and to improve safety along an arterial. Midblock U-turns make it possible to close the + Closed Type 3a median opening at each three-leg intersection and prohibit left-turn movements from driveways along the arterial. Vehi- Combination C7 is similar to Combination C5, except that cles must make left-turn movements by turning right onto the Combination C7 has a conventional rather than a directional arterial and then making U-turns downstream. The directional midblock median opening. Combination C7 serves the same midblock median opening can accommodate heavy U-turn purposes as Combination C5, but is more appropriate where volumes. This combination is appropriate where conven- U-turn volumes are relatively light. tional median openings at three-leg intersections are experi- encing safety problems such that the most effective treatment Combination C8--Directional Midblock Median is to close the median openings. Opening Between Four-Leg Signalized Intersections With Conventional Median Combination C6--Conventional Midblock Openings But All Left-Turning Median Opening Between Four-Leg Movements Prohibited Intersections Without Median Openings Combination C8 includes a directional midblock median Combination C6 includes a conventional midblock median opening with left-turn lanes between two signalized four-leg opening with left-turn lanes between two four-leg intersec- intersections with conventional median openings, no left-turn Combination C5 = Closed Type 3a + Type 2b + Closed Type 3a Figure 42. Combination C5--directional midblock median opening between three-leg intersections without median openings.

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57 Combination C6 = Closed Type 5a + Type 1b + Closed Type 5a Figure 43. Combination C6--conventional midblock median opening between four-leg intersections without median openings. Combination C7 = Closed Type 3a + Type 1b + Closed Type 3a Figure 44. Combination C7--conventional midblock median opening between three-leg intersections without median openings. Combination C8 = Signalized Type 5a + Type 2b + Signalized Type 5a Traffic Signal Traffic Signal Figure 45. Combination C8--directional midblock median opening between four-leg signalized intersections with conventional median openings but all left-turning movements prohibited.

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58 lanes, and all left-turning movements prohibited. This com- onto the arterial and then making U-turns downstream. bination is illustrated in Figure 45 and is represented as Major-road vehicles must make left-turn or U-turn move- ments by proceeding through the intersection, making U- Combination C8 = Signalized Type 5a + Type 2b turns at the midblock median opening, and turning right onto + Signalized Type 5a the minor road. This combination is appropriate where con- ventional median openings at signalized four-leg intersec- Combination C8 can be used as an alternative to direct left tions are experiencing safety problems such that the most turns in order to reduce conflicts and improve safety along effective treatment is to reduce the number of conflicts by an arterial and to simplify signal phasing at signalized inter- prohibiting turning movements at the intersections. It is gen- sections. Midblock U-turns make it possible to prohibit all erally considered good practice to provide right-turn lanes left turns at the signalized intersections as well as prohibit on all approaches to the signalized intersection to accom- left turns from driveways along the arterial. Minor-road modate the heavy right-turn volumes that are inherent to vehicles must make left-turn movements by turning right indirect left-turn intersections.