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Median Cross-Section Design for Rural Divided Highways (2014)

Chapter: Chapter 3 - State Survey Results

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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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Suggested Citation:"Chapter 3 - State Survey Results." National Academies of Sciences, Engineering, and Medicine. 2014. Median Cross-Section Design for Rural Divided Highways. Washington, DC: The National Academies Press. doi: 10.17226/22032.
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25 C H A P T E R 3 3.1 Survey Method A survey of state highway agencies concerning their median design practices was conducted in 2003 as part of NCHRP Project 17-14. This previous survey was updated by a survey conducted as part of the current research. The survey con- ducted as part of the current research, referred to here as the 2006 survey, was not identical to the earlier survey, but did contain several of the same questions relating to typical median cross sections and use of median barriers. Copies of the survey questionnaires for the 2003 and 2006 surveys are presented in Appendices A and B, respectively, which are not provided herein but are available on the TRB website and can be found there by searching for NCHRP Report 794. Both the 2003 and 2006 surveys were sent to the design engineers of the 50 state highway agencies. The 2006 survey used a Web-based approach that allowed the questions asked to be based on the responses to earlier questions. To avoid duplication of effort, survey respondents were first asked whether their median design policies had changed since 2003. If the agency had responded to the 2003 survey and their response to this first question in the 2006 survey indicated that the agency’s median design policies had not changed since 2003, many of the subsequent questions that had already been answered in the previous survey were omitted. The summary of survey results that follows is based on the combined results of the 2003 and 2006 surveys for all cases in which common questions were asked. 3.2 Response Rate The 2003 survey received responses from 35 of the 50 states, or 70 percent. The 2006 survey also received responses from 35 of the 50 states, or 70 percent. There were 28 states that responded to both surveys. There were nine states that responded to the 2003 survey, but not to the 2006 survey. There were six states that responded to the 2006 survey, but not the 2003 survey. Thus, the combination of both surveys includes responses from 43 states (or 86 percent). Table 3-1 summarizes the states that responded to one or both of the surveys. Table 3-2 summarizes the responses concerning changes in median design policies from the 28 states that responded to both surveys. The table indicates that approximately half of the highway agencies changed their median design policies since the 2003 survey and half did not. Table 3-3 summarizes the responses from all states to the question in the 2006 sur- vey about changes in design policies since 2003. 3.3 Survey Summary 3.3.1 Typical Cross Sections Agencies were asked to identify their design criteria for median width and median side slope. They could also indi- cate other information about their typical design elements. There were 18 responses to this question in the 2006 sur- vey and 9 responses from the 2003 survey were added. All responses to this question are summarized in Table 3-4. The responses for specific design elements are summarized in the following subsections. 3.3.1.1 Median Widths Table 3-5 shows the distribution of minimum or typical median widths currently used by state highway agencies in freeway design. The minimum median widths in current use range from 8 m (26 ft) (used only for flush medians with median barrier) to 23 m (76 ft). Throughout this report, median width is defined as the distance from the inside edge of the traveled way to inside edge of the traveled way for the opposing roadways of a divided highway. Table 3-6 shows that nine state highway agencies specify desirable median widths for freeways greater than the mini- mum median width used by the same agency. The desirable median widths range from 18 to 38 m (60 to 126 ft). State Survey Results

26 Agencies responding to both 2003 and 2006 surveys Agencies responding to the 2003 survey only Agencies responding to the 2006 survey only Alabama Alaska Idaho Arkansas Arizona Kentucky California Colorado New Mexico Connecticut Hawaii Oregon Delaware Kansas Tennessee Florida Massachusetts Texas Indiana Michigan Iowa New Hampshire Maine North Dakota Maryland Minnesota Mississippi Missouri Montana Nebraska Nevada New Jersey New York North Carolina Ohio Pennsylvania South Carolina South Dakota Virginia Washington West Virginia Wisconsin Wyoming Table 3-1. State highway agencies that responded to one or both surveys. Response Number (percentage) of highway agenciesa No change in policy since 2003 14 (50.0) Policies have changed since 2003 12 (42.8) No response 2b (7.1) Total 28 a Percentage based on 28 agencies that responded to both the 2003 and 2006 surveys. b Although these two agencies did not respond to the question about policy changes since 2003, they included copies of their current policies with their response. Table 3-2. Changes in median design policies between 2003 and 2006 indicated by agencies that responded to both surveys. Table 3-7 shows that four state agencies specify minimum median widths for nonfreeways less than the minimum widths used by the same agency for freeways. The minimum median widths for nonfreeways range from 12 to 15 m (40 to 50 ft). 3.3.1.2 Median Side Slopes Table 3-8 shows that the minimum median side slopes range from 1V:4H to 1V:6H, with 17 of the 19 state highway agencies who responded indicating that they use minimum median side slopes of 1V:6H. Two states stated specifically that they use slopes flatter than 1V:6H in medians with barriers. Table 3-9 shows that four states specify desirable median side slopes flatter than the minimum median side slopes. The desirable median side slopes ranged from 1V:6H to 1V:12H. In addition, two states specified that median side slopes flat- ter than their minimum value of 1V:6H are preferred. Only one state uses different values of desirable median side slope for freeways and nonfreeways. Texas uses a desirable side slope of 1V:8H for nonfreeways while the desirable side slope for freeways is 1V:12H; the minimum side slope for both freeways and nonfreeways in Texas is 1V:6H. 3.3.2 Median Barrier Warrant Criteria Highway agencies were asked in both the 2003 and 2006 surveys if they used the median barrier warrants in the 2002 AASHTO Roadside Design Guide (see Figure 2-3). Table 3-10 indicates that 20 of the 30 states (66.7 percent) that responded to the question in at least one of the two surveys indicate that

27 they use the AASHTO median barrier warrants. Ten of the 30 responding states (33.3 percent) indicate that they did not use the AASHTO median barrier warrants. The responses are shown in Table 3-11. All responses shown in Table 3-11 are from the 2006 survey, except where responses to the 2003 survey are specifically noted. At the time of the survey, the revised 2006 AASHTO median barrier warrants had just been published, so highway agencies had not yet had time to decide whether to adopt these warrants. Table 3-12 summarizes the median barrier warrant crite- ria of the 10 states that indicated that they do not use the 2002 AASHTO criteria. Where more than one criterion is used by an agency, multiple columns appear in Table 3-12. Factors other than median width considered in these criteria included ADT, posted speed limit, cross-median crash rates, location within 1 mile of entrance/exit ramp gore areas, and roadway type (freeway versus nonfreeway). For criteria based on median width alone, minimum median widths where barriers are not required ranged from 5 to 20 m (18 to 64 ft). One state (Maryland) stated that they do not install barrier if the median is more than 23 m (75 ft) wide. Five agencies specified median widths in conjunction with ADT. In Maryland, medians up to 23 m (75 ft) in width would require barriers if the ADT was greater than 80,000 vehicles per day. One agency considers both median width and speed and requires barrier if the median width is less than 15 m (50 ft) and the posted speed limit is greater than 72 km/h (45 mph). Another agency stated specifically that median barrier is not placed on collectors or other highways without access control. All of these 10 state highway agencies that have median barrier warrants that differ from the 2002 AASHTO warrants require barrier in more situations than AASHTO, and most require median barrier in more situations than the updated 2006 AASHTO warrants. 3.3.3 Approved Median Barriers Both surveys asked highway agencies which median barrier types are approved for use and in what situations each barrier type was used. A total of 28 responses were received to this question, 19 responses in the 2006 survey, and 9 responses in the 2003 survey. Table 3-13 summarizes the number of states that approve use of specific median barrier types. Table 3-14 shows the median barrier types approved for use in specific states. Some agencies have as many as six approved median barrier types. The barrier type used by the most agencies was the W-beam guardrail (23 of 29 responding agencies). The F-shaped and New Jersey concrete barrier are approved for use by 15 agen- cies; the single-slope concrete barrier is approved for use by 12 agencies; and high-tension cable barrier is approved for use by 13 agencies. High-tension cable barrier use is much higher in 2006 than reported in 2003. The survey also asked each state highway agency whether they had any approved median barrier types other than those listed in the survey. Only one state (New York) identified an additional approved median barrier type. In New York, steel- backed timber rail is approved for use as a median barrier. 3.3.4 Minimum Median Widths for Use of Median Barriers Each responding agency was asked to state the minimum medium width in which each barrier type is used. The range of minimum median widths for each barrier type is shown Agency Response Alabama No change. The 2003 responses are still current. Arkansas Did not respond to this question. California No change. The 2003 responses are still current. Connecticut No change. The 2003 responses are still current. Delaware Policies or practices have changed since 2003. Florida Did not respond to this question. Idaho Did not respond to the 2003 survey. Indiana Policies or practices have changed since 2003. Iowa Policies or practices have changed since 2003. Kentucky Did not respond to the 2003 survey. Maine No change. The 2003 responses are still current. Maryland Did not respond to the 2003 survey. Michigan No change. The 2003 responses are still current. Minnesota Policies or practices have changed since 2003. Mississippi No change. The 2003 responses are still current. Missouri Policies or practices have changed since 2003. Montana No change. The 2003 responses are still current. Nebraska Policies or practices have changed since 2003. Nevada No change. The 2003 responses are still current. New Jersey Policies or practices have changed since 2003. New Mexico No change. The 2003 responses are still current. New York Policies or practices have changed since 2003. North Carolina No change. The 2003 responses are still current. Ohio No change. The 2003 responses are still current. Oregon Did not respond to the 2003 survey. Pennsylvania No change. The 2003 responses are still current. South Carolina No change. The 2003 responses are still current. South Dakota Policies or practices have changed since 2003. Tennessee No change. The 2003 responses are still current. Texas Did not respond to the 2003 survey. Virginia Did not respond to the 2003 survey. Washington Did not respond to the 2003 survey. West Virginia Policies or practices have changed since 2003. Wisconsin Policies or practices have changed since 2003. Wyoming Policies or practices have changed since 2003. Table 3-3. Response from specific agencies about changes in median cross-section design policies since 2003.

28 Agency Response Median width Median side slopes Other Alabama (2003) Use AASHTO Guidelines California (2003) 60 ft desirable 1V:10H desirable, 1V:6H min Delaware 40-ft min; wider is desirable where r/w permits 1V:6H or flatter Florida Non-limited-access rural: 40 ft; Interstate: 64 ft; other freeways: 50 ft; limited access with barrier: 26 ft 1V:6H Idaho 100 ft between roadway center lines, typically 38 ft from edge travel way to median center w/ 4-ft paved shoulder. 1V:6H Indiana 26 ft in paved flush median; 60 ft typical, or 80 ft in some new construction where site conditions allow in graded earth medians 1V:5H max Where median barriers are present, median side slopes should be 1V:10H or flatter in graded median, 1V:24H in paved median Iowa 64 ft 1V:6H Kentucky 40 ft 1V:6H Maine (2003) 1V:6H Minnesota 40 ft 1V:4H to 1V:6H Mississippi (2003) Use AASHTO Guidelines Missouri 60 ft 1V:6H Montana (2003) 36 ft min to 75 ft desirable Nebraska 64 ft to 76 ft 1V:6H 12-ft left shoulders on 6-lane facilities Nevada (2003) Use AASHTO Guidelines New Jersey 4 ft min to 84 ft desirable 1V:12H most common; 1V:6H max Use Concrete Barrier Curb (CBC) for median width up to 12 ft. Prefer CBC for medians 13 to 26 ft, but may also use dual faced beam guide rail (DFBGR). Use DFBGR for 26 to 60 ft median. New York No typical sections No typical sections No typical sections North Carolina (2003) Use AASHTO Guidelines Ohio (2003) Use AASHTO Guidelines Oregon Rural 76 ft, 126 ft preferred; nonfreeway: 76 ft; 46 ft min in constrained area No steeper than 1V:6H, slope values dependent on fill height Pennsylvania (2003) Use AASHTO Guidelines South Carolina 48-ft min 1V:6H South Dakota Variable as it depends on project conditions; 80-ft preferred and 42- ft min 1V:6H, toe at 30 ft clear zone 1V:20H from toe of 1V:6H slope to centerline of median Texas Freeways: 76 ft; multilane divided: 76 ft desirable Freeways: 1V:12H des; 1V:6H min. Multilane divided: 1V:8H des; 1V:6H Concrete median barrier not to be placed on slopes steeper than 1V:10H. High-tensioned cable barrier not to be placed on slopes steeper than 1V:6H. Washington 40 ft to 60 ft (width is influenced by the number of lanes and the type of access control) Not steeper than 1V:6H West Virginia 46 ft 1V:6H Wisconsin 60 ft for 65 mph posted speed, 50 ft for 55 mph posted speed 1V:6H Wyoming 76 ft preferred 1V:6H or flatter preferred Table 3-4. Survey responses concerning median cross-section elements.

29 Minimum median width (ft) Number of state highway agencies 26 1a 36 1 40 4 42 2 46 2 48 1 60 3 64 3b 76 3 20 a Minimum 26-ft width used only for flush median with median barrier. b One state with a minimum 64-ft median for the Interstate system permits 50-ft medians on non Interstate freeways and 26-ft flush medians with median barriers. Table 3-5. Minimum or typical median widths used in freeway design. Desirable median width (ft) Number of state highway agencies 60 2 65 1 76 2 80 2 84 1 126 1 9 Table 3-6. Desirable median widths used in freeway design. Minimum median width (ft) Number of state highway agencies Nonfreeways Freeways 40 64a 1 46 76 1 48 76 1 50 60b 1 4 a Minimum 50-ft median width permitted for noninterstate freeways. b Minimum 60-ft median width for 65-mph freeways; 50-ft medians used for 55-mph freeways and nonfreeways Table 3-7. Minimum median widths for nonfreeways less than minimum median widths for freeways. Minimum median side slope Number of state highway agencies 1V:4H 1 1V:5H 1 1V:6H 18a,b 20 a One state uses minimum median slope of 1V:10H in graded median where barrier is present and 1V:24H in paved median. b One state uses minimum median slope of 1V:10H in median with concrete median barrier. Table 3-8. Minimum median side slopes used in freeway design. Median side slope Number of state highway agenciesDesirable Minimum 1V:6H 1V:4H 1 1V:10H 1V:6H 1 1V:12H 1V:6H 2a, b Flatter than 1V:6H preferred 2 6 a One state most commonly uses 1V:12H median slopes, but permits use of minimum 1V:6H slopes. b One state uses 1V:8H desirable median slopes on nonfreeways. Table 3-9. Desirable median side slope use in freeway design. Does your agency use the 2002 AASHTO median barrier warrants? Number (percentage) of state highway agencies Yes 20 (66.7) No 10 (33.3) 30 Table 3-10. Highway agency usage of the 2002 AASHTO median barrier warrants.

30 Agency Does your agency use the 2002 AASHTO median barrier warrants? Alabama (2003) Yes California (2003) No Delaware Yes Florida No Idaho Yes Indiana Yes Iowa Yes Kentucky Yes Maine (2003) No Maryland No Minnesota Yes Mississippi (2003) Yes Missouri Yes Montana (2003) Yes Nebraska Yes Nevada (2003) Yes New Jersey No New York No North Carolina (2003) No Ohio (2003) Yes Oregon No Pennsylvania Yes South Carolina Yes South Dakota Yes Texas Yes Virginia Yes Washington No West Virginia Yes Wisconsin No Wyoming Yes Table 3-11. Response from specific agencies on whether they use the 2002 AASHTO median barrier warrants. in Table 3-15 and the specific responses from each state high- way agency are shown in Table 3-16. Table 3-16 also shows the barrier types for which responding agencies did not identify a specific minimum median width. The minimum median widths for use of different barrier types varied with the barrier system’s rigidity. For concrete barriers, minimum medium widths of 0.6 to 8 m (2 to 26 ft) were required; for metal guardrails, the minimum median widths ranged from 1.2 to 13 m (4 to 41 ft). For high-tension cable barriers, mini- mum median widths ranged from 5 to 15 m (15 to 50 ft) and for three-strand cable barriers, the minimum median width ranged from 7 to 14 m (22 to 46 ft). 3.3.5 Median Barrier Placement Criteria Highway agency responses concerning the placement of median barriers are presented in Table 3-17. Median barri- ers are generally placed either in the center of the median or along the median shoulder. Concrete barrier is typically placed in the center of the median. Guardrail is typically placed in the center of the median if slopes are flat and on the shoulder otherwise. Cable barriers are typically placed in the center of the median or upslope from the low point of the median cross section. Cable barriers can be used on steeper side slopes than other barriers (see next section); however, vehicles can go under the cable barriers if they approach the barrier when their suspension is fully compressed, as when the vehicle crosses the low spot in the median. 3.3.6 Maximum Side Slope for Use of Median Barrier Highway agency responses concerning the maximum side slopes where approved barriers may be installed are shown in Table 3-18. The responses indicate that guardrail and concrete barrier are not normally used where side slopes are steeper than 1V:10H. Where steeper slopes are present, barriers are typically placed near the shoulder of the roadway. A few agen- cies indicated that guardrail or concrete barriers could be used on slopes as steep as 1V:6H. Most of the responding agencies indicated that they would use either of the cable barriers on 1V:6H slopes and two agencies indicated that they would use high-tension cable barrier on slopes as steep as 1V:4H. 3.3.7 Distribution of Barrier Usage by Barrier Type Highway agencies were asked to estimate their current usage of each median barrier type only in the 2006 survey. Usage estimates are presented in Table 3-19. F-shaped and New- Jersey-shaped concrete barriers have the greatest reported usage in agencies where they are approved. W-beam guardrail also has heavy usage in some agencies. Although the use of high- tension cable barrier is increasing, it is only used extensively by two agencies according to the survey responses. Three-strand cable barriers have generally had little usage except in one state among the states that responded to the question. 3.3.8 Ditch Cross Sections The 2006 survey asked about ditch cross sections used by state highway agencies in divided highway medians. There were 19 responses to this question; 12 agencies indicated typi- cal cross sections for ditches in medians, and responses are shown in Table 3-20. Responses to this question varied, because some agencies indicated the total median widths they use and others indicated dimensions for ditches with the median. The typical widths identified for ditches within the median were 1.2, 1.8, and 3.0 m (4, 6, and 10 ft); other responses indicated variable ditch widths. Ditch slopes were mainly listed as 1V:6H, and others listed were as steep as 1V:4H. The ditch depths listed varied from 0.2 to 1.4 m (0.5 to 4.6 ft).

31 Agency Response Median barrier criteria California (2003) Conduct study if median width is 0 to 20 ft and ADT exceeds 20,000 veh/day Conduct study if median width is less than 75 ft and ADT exceeds 60,000 veh/day Study any median with 0.5 cross-median crashes per mile per year or 0.12 fatal crashes per mi per year Florida On Interstate, install barrier if median width less than 64 ft; 50 ft on other freeways On Interstates and expressways, median barrier is required within 1 mi of exit/entrance gore with one or more cross-median crashes within 5 years Maine (2003) Install barrier if the median width is < 20 ft and ADT > 20,000 Install barrier if median width is < 30 ft and ADT > 30,000 veh/day Barrier optional if width is < 20 ft and ADT is 5,000 to 20,000 veh/day Barrier optional if median width is 30 ft to 50 ft and ADT > 40,000 veh/day Maryland Install median barrier if width <= 30 ft Install median barrier if width > 30 ft but < 50 ft and ADT > 40,000 veh/day Install median barrier if width > 50 ft but < 75 ft and ADT > 80,000 veh/day Do not install barrier if median width > 75 ft New York Install barrier if median width < 36 ft and ADT > 20,000 veh/day Barrier encouraged if median width < 72 ft Barrier is optional if median width is < 45 ft and ADT >10,000 veh/day North Carolina (2003) Install barrier if median width < 70 ft Oregon Install barrier if median width less than or equal to 60 ft; over 60 ft, base warrant on cross-median collision statistics Virginia 18 ft Washington Provide median barrier on multilane highways with full access control with median widths of 50 ft or less and posted speeds of 45 mph or more Consider median barrier on highways with wider medians or lower posted speeds when there is a history of cross-median accidents Median barrier is not normally placed on collectors or other state highways that do not have limited-access control Wisconsin On new freeway construction: range (median width, ADT) from (< = 20 ft, > = 20,000 veh/day) to (< 60-ft, > = 50,000 veh/day) No retrofit warrant Table 3-12. Median barrier criteria. Median barrier type Number (percentage) of state highway agencies that currently approve each median barrier type for use on rural divided highwaysa Weak-post W-beam guardrail 4 (13.8) Box-beam barrier 3 (10.3) Blocked-out W-beam guardrail (strong post) 23 (79.3) Blocked-out Thrie-beam guardrail 10 (34.5) Modified Thrie-beam guardrail 4 (13.8) New-Jersey-shaped concrete barrier 15 (51.7) Single-slope concrete barrier 12 (41.4) F-shape concrete barrier 15 (51.7) Three-strand cable barrier (weak post) 8 (27.6) High-tension cable barrier 13 (44.8) a Based on response from 29 state highway agencies; responses sum to more than 100 percent because most states use more than one barrier type. Table 3-13. State highway agency usage of specific median barrier types.

Median barrier types currently approved for use on rural divided highways Weak-post W-beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam guardrail New-Jersey- shaped concrete barrier Single-slope concrete barrier F-shaped concrete barrier Three-strand cable (weak post) High-tension cable barrier Alabama (2003) X X X X Arkansas X X X X X California (2003) X X Delaware X Florida X X X Idaho X X X Indiana X X X Iowa X X X X Kentucky X X X Maine (2003) X X X Maryland X X X X Minnesota X X X X X Mississippi (2003) X X X X Missouri X X X X X X Montana (2003) X Nebraska X Nevada (2003) X X X X New York X X X X X X North Carolina (2003) X X X X Ohio (2003) X X X X Oregon X X X X X Pennsylvania (2003) X X X South Carolina x x South Dakota X X X X X Texas X X X X Virginia X X X Washington X X X X X Wisconsin X X X X Wyoming X X X X X X Table 3-14. Approved median barrier types for specific state highway agencies.

33 Median barrier type Range of minimum median widths (ft) for use of specific median barrier types Weak-post W-beam guardrail 18 Box-beam barrier 10 to 14 Blocked-out W-beam guardrail (strong post) 5.5 to 41 Blocked-out Thrie-beam guardrail (strong post) 4 to 26 Modified Thrie-beam guardrail 8 to 30 New-Jersey-shaped concrete barrier 2 to 24 Single-slope concrete barrier 2 to 18 F-shaped concrete barrier 2 to 26 Three-strand cable barrier (weak post) 22 to 46 High-tension cable barrier 15 to 50 Table 3-15. Range of minimum median widths for use of specific median barrier types. 3.3.9 Typical Median Cross Sections Highway agencies responding to the 2006 survey were asked to provide typical cross sections for divided highways. This question was not asked in the 2003 survey. Typical cross sections provide useful information because they show the entire set of dimensions used in median cross-section design. There were 16 responses to this question, as indicated in Table 3-21. The median widths for these typical cross sections range from 12 to 38 m (38 to 126 ft); median shoulder widths vary from 1.2 to 5 m (4 to 15 ft); side slopes range from 1V:4H to 1V:12H; ditch widths vary from 0 to 9 m (0 to 28 ft); and ditch depths range from 0.3 to 1.4 m (1 to 4.6 ft). 3.3.10 Safety Performance Evaluations Responding agencies were asked if they had conducted any safety performance evaluations of median cross-section features and were asked to provide copies of any evaluations they had completed. Information was received from four agencies, as follows: • Iowa: High-tension cable barrier study; • Missouri: Comprehensive guard cable study; • Oregon: Sent proposed policy for Interstate median clo- sures; and • Washington: Sent information on comparison of barrier collisions. The results of these studies are reviewed in Section 3.4. 3.3.11 Additional Materials The following seven highway agencies sent other materials on design such as policies, procedures, or published materials: • California: Two reports on median barrier warrants; • Indiana: Design manual excerpts; • Kentucky: Draft guidelines on median barrier applications on fully controlled-access highways; • New York: Highway design manual link; • South Dakota: Information on median barrier use and link to design manual; • Virginia: Referred to AASHTO Roadside Design Guide; and • Wyoming: Standards engineer contact information. 3.3.12 State Highway Agencies Willing to Furnish Data Respondents were asked whether they would be willing to furnish crash and roadway inventory data for the research, if asked. Twenty of the 29 responding agencies indicated that they would be willing to furnish data. The agencies that indicated that they would be willing to furnish data for the research were as follows: 1. Alabama, 2. Nevada, 3. California, 4. New Mexico, 5. Iowa, 6. North Carolina, 7. Kentucky, 8. Ohio, 9. Maine, 10. Oregon, 11. Maryland, 12. Pennsylvania, 13. Minnesota, 14. Texas, 15. Missouri, 16. Washington, 17. Montana, 18. Wisconsin, 19. Nebraska, and 20. Wyoming. (text continued on page 43)

Agency Minimum median width (ft) for use of specific barrier types Weak-post W-beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam New-Jersey- shaped concrete barrier Single-slope concrete barrier F-shaped concrete barrier Three-strand cable (weak post) High-tension cable barrier Alabama (2003) 8 6.5 6.5 32 Arkansas 30 18 18 18 16 California (2003) 20 a Delaware 10 Idaho 10 10 5 Indiana 30 30 26 Iowa 14 14 a Kentucky 18 18 30 Maine (2003) 26 26 22 Maryland 6 6 2 2 Minnesota 10 10 10 10 15 Mississippi (2003) 24 24 24 24 Missouri 8 4 2 2 24 16 Montana (2003) 9 Nebraska 50 Nevada (2003) b b a 24 New York 2 2 22 North Carolina (2003) a 36 a 46 Ohio (2003) 5.5 a a 15 Oregon 10 8 8 8 20 Pennsylvania (2003) a a a Texas 10 10 10 25 Virginia 18 18 6 Washington 14 14 14 25 Wisconsin 41 a 41 41 Wyoming 14 12 12 10 10 16 a No formal minimum median width specified. b Minimum median width based on dynamic deflection distance for specific barrier type. Table 3-16. Minimum median width for use of specific median barrier types.

Agency Most common placement location for each barrier type Weak- post, W- beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam guardrail New- Jersey- shaped concrete barrier Single- slope concrete barrier F-shaped concrete barrier Three- strand cable (weak post) High-tension cable barrier Alabama (2003) Shoulder break Center of median Center of median 4 ft upslope from ditch Arkansas Face of guardrail 2 ft from outside edge of shoulder Face of barrier 2 ft from outside edge of shoulder Face of barrier 2 ft from outside edge of shoulder Face of barrier 2 ft from outside edge of shoulder Center of median California (2003) Center of median Center of median Delaware Center of median Idaho 2 ft from face of rail to roadway normal shoulder 2 ft from face of rail to roadway normal shoulder 1.33 ft from face of rail to roadway normal shoulder Indiana Center of median or offset for drainage considerations Center of median or offset for drainage considerations Center of median Iowa Center of median Center of median Center of median Placed 2 ft off edge of shoulder Kentucky Edge of shoulder Center of median 10 ft from edge of shoulder on slopes flatter than 1V:6H Maine (2003) Center of median Center of median Center of median Maryland On slopes 1V:10H or flatter, as far away from the travel lane as possible. For slopes steeper than 1V:10H, either 2 ft from shoulder or 12 ft from shoulder At the edge of the shoulder; used when approaching bridge parapets Center of median Center of median Minnesota Variable depending on Vary depending on shoulder and/or SSD Vary depending on shoulder Vary depending on shoulder Either 2 ft from paved shoulder edge or just Table 3-17. Median barrier placement criteria. (continued on next page)

Agency Most common placement location for each barrier type Weak- post, W- beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam guardrail New- Jersey- shaped concrete barrier Single- slope concrete barrier F-shaped concrete barrier Three- strand cable (weak post) High-tension cable barrier shoulder and/or SSD needs needs and/or SSD needs and/or SSD needs above ditch bottom on one or the other side slope Mississippi (2003) Center of median Center of median Center of median Center of median Missouri Center of median Center of median Center of median Center of median Center of ditch, vertex of ditch, or 10 ft upslope Center of ditch, vertex of ditch, or 10 ft upslope Montana (2003) Center of median Nebraska 12 ft from driving lane Nevada (2003) 2 ft from paved shoulder 2 ft from paved shoulder Center of narrow medians and 2 ft from paved shoulder on wider medians > 26 ft Center of median New York Middle Middle Middle Middle Middle Middle North Carolina (2003) Shoulder Shoulder Center of median 4 ft from ditch center Ohio (2003) Center of median Center of median Center of median Center of median Oregon Center of median on slopes flatter than 1V:10H Center of median on slopes flatter than 1V:10H Center of median on slopes flatter than 1V:10H Center of median on slopes flatter than 1V:10H, at edge of shoulder high side in a split elevation Prefer center of median on slopes flatter than 1V:10H, may be used on 1:6 slopes if needed Pennsylvania (2003) Center of median Center of median Center of median South Carolina 4 ft from ditch center South Dakota Center of median (used with flush Center of median (used with Center of median (used with Center of median (used with flush 1 ft from center of median on 1V:6H slope; Table 3-17. (Continued).

Agency Most common placement location for each barrier type Weak- post, W- beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam guardrail New- Jersey- shaped concrete barrier Single- slope concrete barrier F-shaped concrete barrier Three- strand cable (weak post) High-tension cable barrier medians) flush medians) flush medians) medians) preferred at center of median on 1V:10H and flatter slope; Texas Center of median Center of median Center of median 8 to 12 ft from travel lane on slopes 1V:6H or flatter Virginia Center of median Center of median Center of median Washington Alongside shoulder Alongside shoulder or in the center of flatter paved medians In the center of flatter paved medians In the low point, or at least barrier deflection distance away from closest lane edge In the low point, or at least barrier deflection distance away from closest lane edge Wisconsin Edge of shoulder Edge of shoulder Has been center of median but are re- considering At least 8 to 10 ft from ditch; and beyond edge of shoulder far enough to (1) allow vehicles to pull completely off the travel lane and (2) prevent design deflection from encroaching into travel lanes Wyoming Center of median with slopes 1V:10H or flatter Center of median with slopes 1V:10H or flatter Center of median if median slope 1V:10H Center of median with flat slope or normal crown Center of median with flat slope or normal crown Minimum of 8 ft off edge of traveled way or 8 ft from center of V-shaped median with 1V:6H or flatter median slope Table 3-17. (Continued).

Agency Maximum median side slope on which the specified barrier is installed Weak- post W- beam guardrail Box-beam barrier Blocked-out W- beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie- beam guardrail New-Jersey- shaped concrete barrier Single-slope concrete barrier F-shaped concrete barrier Three- strand cable (weak post) High-tension cable barrier Arkansas 1V:25H 1V:25H 1V:25H 1V:25H 1V:6H Delaware 1V:10H Idaho Barrier placed off shoulder with the paving surface extended to the barrier; cross- slope matches slope of roadway, end terminals may have slope of 1V:10H for flares Barrier is placed off shoulder with the paving surface extended to the barrier; cross- slope matches slope of roadway; end terminals may have slope of 1V:10H for flares Barrier is placed off shoulder with the paving surface extended to the barrier; cross-slope matches slope of roadway; end terminals may have slope of 1V:10H for flares Indiana 1V:6H max; 1V:10H or flatter desirable 1V:6H max; 1V:10H or flatter desirable Barrier is plumb with adjacent shoulder slope; typically 1V:24H except in curves where shoulder slope might be 1V:12H. Iowa 1V:10H 1V:10H 1V:33H (3%) 1V:6H Kentucky 1V:10H 1V:10H 1V:4H Maryland N/A; where the slope is steeper than 1V:6H, barrier is placed at edge of shoulder N/A; when the slope is steeper than 1V:6H barrier is placed at edge of shoulder 1V:10H 1V:10H Minnesota 1:10 (but typically curbed application) N/A; typically curbed application N/A; typically curbed application N/A; typically curbed application 1V:6H or steeper if allowed by manufacturer’s recommendation Missouri 1V:6H 1V:6H 1V:6H 1V:6H 1V:6H 1V:4H Nebraska 1V:10H New York 1V:8H 1V:8H 1V:8H 1V:10H 1V:10H 1V:6H Table 3-18. Maximum side slopes for median barrier use.

Agency Maximum median side slope on which the specified barrier is installed Weak- post W- beam guardrail Box-beam barrier Blocked-out W- beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie- beam guardrail New-Jersey- shaped concrete barrier Single-slope concrete barrier F-shaped concrete barrier Three- strand cable (weak post) High-tension cable barrier Oregon 1V:10H 1V:10H 1V:10H 1V:10H 1V:6H South Carolina 1V:10H 1V:6H South Dakota Prefer 1V:50H; max 1V:10H Prefer 1V:50H; max 1V:10H Prefer 1V:50H; max 1V:10H Prefer 1V:50H; max 1V:10H Prefer 1V:10H or flatter; Max 1V:6H Texas 1V:10H 1V:10H 1V:10H 1V:6H Virginia 1V:6H 1V:6H 1V:6H Washington 1V:10H or flatter, or placed at least 12 ft from shoulder edge with a slope between 1V:6H and 1V:10H 1V:10H or flatter, or placed at least 12 ft from shoulder edge with a slope between 1V:6H and 1V:10H 1V:10H or flatter, or placed at least 12 ft from shoulder edge with a slope between 1V:6H and 1V:10H Not steeper than 1V:6H Not steeper than 1V:6H Wisconsin Shoulder slope Shoulder slope 1V:6H 1V:6H Wyoming 1V:10H 1V:10H 1V:10H Flat or normal crown Flat or normal crown 1V:6H min; 1V:8H or flatter preferred Table 3-18. (Continued).

Agency Current agency usage (percent) of each of the approved barrier types Weak-post W-beam guardrail Box-beam barrier Blocked-out W-beam guardrail (strong post) Blocked-out Thrie-beam guardrail (strong post) Modified Thrie-beam guardrail New-Jersey- shaped concrete barrier Single-slope concrete barrier F-shaped concrete barrier Three-strand cable (weak post) High-tension cable barrier Arkansas Less than 5% 20% 30% Less than 5% Less than 5% Delaware 100% where barriers are placed in rural medians, which is very seldom Idaho ~ 30% ~ 10% (mostly across structures that do not use a concrete barrier system) ~ 60% Indiana 19% 1% 80% Iowa 1% 0% 60% 40% Kentucky 19% 80% 1% Maryland 75% 5% 10% 10% Minnesota 5% 5% 5% 5% 80% Nebraska 1% New York 15% 25% 25% 25% 10% 0 Oregon 5% 0% (to date) 5% 85% 5% South Carolina Majority South Dakota 3% 92% 5% 0% 0% Texas 50% 30% 5% 15% Virginia 20% 20% 10% Wyoming 40% 40% 5% 5% 5% 5% Table 3-19. Distribution of barrier usage by barrier type.

Agency Response Width (ft) Slopes Depth (ft) Delaware 60 ft preferred 1V:6H or flatter Indiana V-shaped ditch is typical; 4-ft wide flat bottom ditch with 1V:5H side slopes 1V:6H or flatter typical; 1V:5H w/ flat bottom ditch 4.2 ft max typical; 4.6 ft max (w/flat bottom ditch) Iowa 1V:50H 4 ft Kentucky Varies 1V:6H 2.8 ft for earth shoulder, 2.58 ft for paved shoulder Minnesota Varies 1V:4H to 1V:6H 3 ft typical Missouri 8 ft 1V:5.5H 4 ft Nebraska 10 ft min 1V:6H 3 ft Oregon 6 ft, one on each side of median 1V:6H 0.5 ft South Carolina 28 ft 1V:6H 2.3 ft Washington Varies 1V:6H 2 ft Wisconsin 0 1V:6H max 1 ft below subgrade shoulder Wyoming 76 ft preferred for new projects 1V:6H min; 1V:8H or flatter preferred 2 ft min Table 3-20. Responses from specific agencies about ditch cross sections used in medians.

Agency Dimensions used in typical median cross sections Median width (ft) Median shoulder width (ft) Median side slope Ditch width (if specified) Ditch depth (if specified) Arkansas 60 6 1V:6H NA 1.5 ft below subgrade Delaware 60 4 1V:6H Idaho 38 4 1V:6H At least 0.5 ft below roadway ballast section Indiana 60 4 1V:5Ha 4 ft for flat bottom ditchb Approx. 4.2 ftc Iowa 64 6 1V:6H 4 ft Kentucky 40 6 1V:6H Varies 2.8 ft for earth shoulder; 2.58 ft for paved shoulder Minnesota 60 4 1V:4H to 1V:6H 8 ft 3 ft Missouri 60 4 1V:6H 8 ft 4 ft Nebraska 64 6 1V:6H 10 ft min 3 ft South Carolina 48 10 1V:6H 28 ft 2.3 ft South Dakota 26 4 1V:6H Texas 76 4 1V:12H Virginia 60 15 1V:10H Based on hydrology Based on hydrology Washington 40 4 1V:6H 2 ft Wisconsin 60 6 1V:6H 0 1 ft below shoulder subgrade Wyoming 76 4 1V:6H or flatter Not specified—use normal rounding 2 ft min; 3 ft or greater preferred a Applicable to graded median; 1V:24H side slope used in flush paved median. b No ditch width given for graded median with V-shaped ditch. c Applicable to graded median with V-shaped ditch; approximately 4.6-ft width used for graded median with flat bottom ditch. Table 3-21. Responses from specific agencies about typical cross sections for divided highway medians.

43 3.4 In-Service Performance Evaluations and Unpublished Reports The Iowa Department of Transportation and the Ohio Department of Transportation submitted reports of the use of the Brifen Wire Rope Safety Fence (WRSF). Tabulations of median-related crashes were received from the Oregon Department of Transportation and the Washington State Department of Transportation. These studies are summa- rized in the remainder of this section. 3.4.1 Iowa Department of Transportation Iowa DOT installed Brifen Wire Rope Safety Fence on I-35 north of Des Moines in December 2003. The barrier was installed just inside the southbound shoulder of the freeway. Posts were set in socketed sleeves to enable easy replacement of posts damaged in crashes. In the period from Decem- ber 2003 to August 2005, there were 20 reported accidents involving the cable barrier system. There were no fatalities or cross-median crashes. There was one injury crash where a vehicle impacted a semi-tractor trailer and then rolled over the barrier. The barrier was impacted by both northbound and southbound vehicles, although southbound crashes were more frequent due to the location of the barrier near the southbound shoulder. Iowa DOT was pleased with the performance of the bar- rier and installed a second system on a non-controlled-access highway in Cedar Falls. Issues raised in the report included: 1. Difficulty of replacing posts in winter conditions, 2. Bidding of four-strand and three-strand systems under one item, and 3. Ease of snow removal with cable barrier as opposed to con- crete barriers. 3.4.2 Ohio Department of Transportation Ohio DOT evaluated the Brifen Wire Rope Safety Fence (WRSF) and has provided in-service performance reports for the first 2 years of a 3-year evaluation period. A presentation was obtained that reported on all 3 years of the evaluation. ODOT installed the Brifen WRSF on I-75 north of Cincin- nati. The roadway is a 23.3-km (14.5-mi) section of six-lane rural Interstate with an 18-m (60-ft) depressed median with 1V:10H side slopes. The median shoulder width is 1.2 m (4 ft) and the barrier was installed 5 m (15 ft) from the edge of trav- eled way. The roadway has an ADT of 92,000 vehicles per day with 22 percent trucks. ODOT developed a special form for reporting crashes with the barrier system. This form was supplemented with photo and crash report forms. Maintenance reports of repairs to damaged barrier sections also were made. The analysis of median crashes showed a total of 233 crashes in 2 years. No serious injuries or fatalities were expe- rienced in these crashes. The total number of crashes in the 2 years since the cable was installed did increase by 26 percent. ODOT maintenance did experience difficulty in replacing nonsocketed posts and recommended that driven posts be replaced with the socketed type. A summary of crashes over 3 years revealed 13 penetra- tion hits with only 3 from the opposing roadway. Many of the vehicles were spinning when they hit the barrier and at least one vehicle overturned on the barrier. Several trucks hit the barrier with only one recorded penetration. There were no fatal cross-median crashes in the 3-year period after the cable installation. 3.4.3 Washington State Department of Transportation The Washington State DOT has published several reports on median safety. At the time of this writing, they were con- ducting a comparison of barrier collisions with various types of barriers. This data is still being analyzed by WSDOT. 3.4.4 Oregon Department of Transportation The Oregon DOT studied the safety performance of open medians and drafted a revised policy on warrants for median barriers. A plot of accidents occurring on medians without barriers (open medians) is shown in Figure 3-1. The crash data used in Figure 3-1 was furnished to the proj- ect team. 3.5 Analysis of Trends in the State of Median Design Only about one-third of the responding agencies have not changed their median design practices in some way since 2003. This in itself is evidence that median design practice and use of median barriers is changing rapidly. If the 2006 survey results are contrasted with those of the 2003 survey, several specific changes are evident. First, agencies are now placing median barriers on wider medians than in the past. For example, Maryland now installs median barriers in 23-m (75-ft) medians if the ADT of the roadway is 80,000 vehicles per day or greater. In other states, the median widths used for median barrier warrants on high- ADT routes were 20, 18, and 15 m (64, 60, and 50 ft). The direction of this trend is generally consistent with Chapter 6 of the AASHTO Roadside Design Guide, which calls for median barrier to be considered on controlled-access roadways

* Denotes opposite direction impactAverage Daily Traffic (ADT) 0 20 40 60 80 100 120 0 20000 40000 60000 80000 100000 120000 140000 160000 W i d t h o f M e d i a n ( f t . ) PDO Injury Fatal *p *f *f (3X) *i *i*i *f *f *i *i *p *i *f(2X) *i *i *p 148 miles 1 acc./2 1 fat./30 1 X- head./ 124 miles 1 acc./1.5 1 fat./25 mi. 1 X-head./ 25 mi. 27 1 acc./1 1 1 X-head/ 5.4 mi. Figure 3-1. Summary of traversable median crashes on Oregon divided highways (2002–2005) (Oregon DOT).

45 when medians are 15 m (50 ft) or less and ADTs are over 20,000 vehicles per day. Second, it is evident that many more agencies have approved the use of high-tension cable median barrier. Five manufacturers of this type of barrier are now listed in the AASHTO Roadside Design Guide and its use is approved in 13 of the highway agencies that responded to the 2006 sur- vey. According to the survey, there is less use of three-strand cable barrier than in 2003. This may be due to more com- petition in high-tension cable barriers, or to the high cost of maintenance for the three-strand cable barriers. There have been some changes in the placement criteria for both types of cable barrier. Some agencies are now specifying placement 2.4 to 3 m (8 to 10 ft) upslope from the low point of the median. This placement is meant to minimize crashes that may go under some cable barrier designs. However, vari- ous policies on barrier placement indicate that many agen- cies are still unsure of how to best use the new cable barrier designs. There were no major changes in typical median cross sec- tions. Median width and median side slopes dimensions in the 2006 survey were in about the same range as in the 2003 survey. Side slopes seem to be changing only in relation to median barrier usage.

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Median Cross-Section Design for Rural Divided Highways Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 794: Median Cross-Section Design for Rural Divided Highways provides guidelines for designing typical cross-sections for medians on new and existing rural freeways and divided highways. Download NCHRP Report 794: Appendices A-E.

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