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59 CHAPTER 5 DATA COLLECTION AND ANALYSIS This chapter describes the data collection and analysis Collection of Catalog Data efforts conducted as part of the research. The major efforts were a catalog of existing median openings, accident studies Each corridor was visited in the field to collect the follow- of existing median openings, field observational studies of ing information on individual median openings: existing median openings, and human factors evaluation of driver behavior in U-turn maneuvers. Location of median opening (milepost or odometer reading), Cross street name, Type of traffic control, CATALOG OF EXISTING MEDIAN OPENINGS Type of median opening, The first activity of the data collection effort was to create U-turn prohibition, a catalog of median opening designs representative of what Area type (urban/suburban), actually exists in the field. The first task in the creation of a Posted speed limit, catalog was to identify arterial corridors that include median Number of through lanes, openings. The second task was visiting the corridors and col- Presence of left-turn lanes, lecting data on the types of median opening designs. This Presence of offset left-turn lanes, section describes the process of creating a catalog of existing Shoulder type, Median type, median openings and summarizes the catalog data. Median width, Presence of loon, and Level of U-turn activity. Identification of Corridors To identify corridors, the research team contacted highway For each unsignalized median opening, the median opening engineers in five states and requested a list of arterial corri- type was classified according to the categories established in dors that include median opening designs representative of Chapter 4 of this report. that state. The states contacted were as follows: Summary of Catalog Data Colorado, Georgia, This section presents a detailed summary of the unsignal- Michigan, ized median openings included in the catalog. Specifically, the New Jersey, and distribution of unsignalized median openings by state, median New York. opening type, posted speed limit, number of through lanes, presence of special left-turn treatment, shoulder type, median A list of approximately 10 to 20 corridors of varying lengths width and type, and level of U-turn activity are presented. was obtained from each state. In Georgia, all of the corridors The catalog consisted of 62 arterial corridors in seven states. were located in Gwinnett County and are under the jurisdic- The corridors comprised a total length of 552 km (343 mi) of tion of that county. In the other states, the corridors were arterial highway, or an average of 8.9 km (5.5 mi) per corri- under the jurisdiction of the state highway agency and were dor. Data were recorded for 918 unsignalized median open- located in several counties in each state. The research team ings located in the 62 arterial corridors. Not all sites, however, also identified, through personal experience and the use of were included in the tables presented below. For example, 14 state highway maps, corridors within the states of Kansas and of the unsignalized median openings did not fit into any of the Missouri. Overall, corridors were identified in seven states median opening types as outlined in Chapter 4. Also, U-turns throughout the country for collection of detailed information were prohibited at 102 of the unsignalized median openings; for cataloging purposes. given that U-turn maneuvers are the focus of the research,

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60 those median openings were not included in the tables pre- 3d = Conventional median opening with left-turn lanes sented below. Finally, four median openings had five-lane and loons at three-leg intersection cross-sections (i.e., three through lanes in one direction of 4a = Directional median opening for left turns from travel and two in the other). Given that the focus of the acci- major road at three-leg intersection dent and field studies was on unsignalized median openings 4b = Directional median opening for left turns onto major on four-lane and six-lane cross-sections, the four five-lane road at three-leg intersection sites were not included in the tables presented below. Thus, 5a = Conventional median opening without left-turn 806 unsignalized median openings are included in the tables. lanes at four-leg intersection 5b = Conventional median opening with left-turn lanes at four-leg intersection State 6a = Directional median opening for left turns from major road at four-leg intersection Table 16 lists the number of unsignalized median openings 7a = Midblock jughandle to the left for U-turn maneuvers visited in each state. The distribution of sites by state provided 7b = Midblock jughandle to the right for U-turn a good geographical diversity for accident and field studies. maneuvers Table 17 presents the frequency of unsignalized median Median Opening Type openings by median opening type. Table 18 presents the num- ber of unsignalized median openings by state and median Based on the classification of median opening types pre- opening type. sented in Chapter 4, there are a total of 17 typical median opening design as follows: Posted Speed Limit 1a = Conventional midblock median opening without left-turn lanes Table 19 presents the distribution of sites by posted speed 1b = Conventional midblock median opening with left- limit and median opening type. The table illustrates a bal- turn lanes ance between high-speed and low-speed arterials overall, 1c = Conventional midblock median opening with left- with 43 percent of all median openings located on low-speed turn lanes and loons arterials and 57 percent located on high-speed arterials. 2a = Directional midblock median opening without left- turn lanes TABLE 17 Number of unsignalized 2b = Directional midblock median opening with left- median openings by median opening type turn lanes 2c = Directional midblock median opening with left- Number of median openings turn lanes and loons Median opening type (%) 3a = Conventional median opening without left-turn Midblock lanes at three-leg intersection 1a 40 (5.0) 3b = Conventional median opening with one left-turn 1b 22 (2.7) lane at three-leg intersection 1c 6 (0.7) 3c = Conventional median opening with two left-turn 2a 1 (0.1) lanes at three-leg intersection 2b 149 (18.5) 2c 17 (2.1) Three-leg TABLE 16 Number of unsignalized median 3a 102 (12.7) openings by state 3b 91 (11.3) 3c 78 (9.7) Number of median openings 3d 9 (1.1) State (%) 4a 24 (3.0) 4b 0 (0.0) Colorado 61 (8) Georgia 150 (19) Four-leg 5a 94 (11.7) Kansas 137 (17) 5b 159 (19.7) Michigan 244 (30) 6a 14 (1.7) Missouri 111 (14) Jughandle New Jersey 62 (8) 7a 0 (0.0) New York 41 (5) 7b 0 (0.0) Total 806 Total 806 (100.0)

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61 TABLE 18 Number of unsignalized median openings by state and median opening type Cross-Section set left-turn lanes provide improved sight distance; loons pro- vide extra pavement width for U-turn vehicles with a large Table 20 presents the distribution of sites by cross section turning radius; and dual left-turn lanes can be confusing to and median opening type. Most of the arterial corridors rec- some drivers. Of the 806 unsignalized median openings, ommended to the research team by highway agencies were 79 had offset left-turn lanes, 34 had loons, and 3 had dual four-lane arterials; about 10 percent of the sites are located left-turn lanes. on six-lane arterials. Special Left-Turn Treatments Shoulder Type When conducting the site visits, the research team mem- The type of shoulder provided at each of the unsignalized bers noted the presence of offset left-turn lanes, loons, and median openings was noted during the site visits. Table 21 dual left-turn lanes. These special left-turn treatments will be presents the distribution of sites by shoulder type. Most of the considered in the accident and field studies because they can median openings had paved shoulders. influence the safety of an unsignalized median opening. Off- TABLE 20 Number of median openings TABLE 19 Number of median openings by cross section and median opening type by posted speed limit and median opening type Major-road cross-section Median opening type Posted speed limit Median opening type 4-lane 6-lane Low speed High speed Midblock ( 50 mph) ( 55 mph) 1a 40 (5.5) 0 (0.0) Midblock 1b 21 (2.9) 1 (1.2) 1a 3 (0.9) 37 (8.0) 1c 6 (0.8) 0 (0.0) 1b 8 (2.3) 14 (3.0) 2a 1 (0.1) 0 (0.0) 1c 3 (0.9) 3 (0.7) 2b 140 (19.4) 9 (10.6) 2a 0 (0.0) 1 (0.2) 2c 12 (1.7) 5 (5.9) 2b 26 (7.5) 123 (26.7) 2c 8 (2.3) 9 (2.0) Three-leg Three-leg 3a 102 (14.1) 0 (0.0) 3a 23 (6.6) 79 (17.2) 3b 77 (10.7) 14 (16.5) 3b 69 (19.9) 22 (4.8) 3c 68 (9.4) 10 (11.8) 3c 38 (11.0) 40 (8.7) 3d 9 (1.2) 0 (0.0) 3d 9 (2.6) 0 (0.0) 4a 7 (1.0) 17 (20.0) 4a 23 (6.6) 1 (0.2) Four-leg Four-leg 5a 94 (13.0) 0 (0.0) 5a 20 (5.8) 74 (16.1) 5b 134 (18.6) 25 (29.4) 5b 105 (30.3) 54 (11.7) 6a 11 (3.2) 3 (0.7) 6a 10 (1.4) 4 (4.7) Total 346 460 Total 721 85