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29 TABLE 6 Summary of curbbarrier installation practices among the states Distance from edge Distance from face of ID Curb type Barrier type of lane to barrier curb to barrier face 1 A Guardrail 0.6 m 0.15 m 3 A (similar) Strong-post (steel) 2.4 m 0 4 Sloped W-beam 0.6 m 0 6 C W-beam 0.6 to 3.7 m 0 8 Asphalt dike W-beam 0.6 to 3.0 m 0 9 Asphalt (100-mm max) W-beam 1.8 to 3.0 m 0 10 A Guardrail 2.4 m 0 11 Vertical and sloped W-beam or T-beam 3.0 m 2.4-3.0 m 12 B or G W-beam Varies 0 or 0.23 m 13 B W-beam Varies 0-0.23 m 14 A W-beam 0.3 m 0 15 G (similar) W-beam Varies 0.05 m or 0.25 ma Strong-post, steel- 16 B and G Varies 0 plate 17 B Guardrail 2.4 or 3.0 m 0 18 100-mm limit W-beam 1.2 or 3.0 m 0 or 0.6 m behind post 18 100-mm curb Raised median 1.2 or 3.0 m 0 or 0.6 m behind post Steel-plate beam, 19 A or G Shoulder (1.8-3.0 m) 0 or behind guardrail concrete Sloped or vertical (100- 20 W-beam Varies 0 or behind guardrail mm max) b 21 A F-shape concrete Shoulder (2.4 m) Behind barrier or 3 m 22 C Guardrail 0.3 m 0 23 Sloped W-beam Shoulder 0 or >0.46 m 24 Auxiliary type VI Variesc Varies 3.0 m 25 Shoulder berm gutter Guardrail Shoulder Under guardrail 26 Sloped (50 mm) Guardrail Varies 0-.3 m Strong-post (steel) 27 C Varies 0 blocked-out or 3-cable a If curb/gutter is outside paved shoulder, 50 mm; when it contacts the lane, 250 mm. b The transition is rolled down from barrier to curb. c Varies, but not cable, concrete barriers, or attenuating devices. binations that they would like to see addressed in this research Usage of impact attenuators on medians, project. Most indicated that they needed more guidance on Curbbarrier combinations at bridge approaches with the use of curbs and curbbarrier combinations at various bridge rails, speeds and functional classes, especially for high-speed facil- Safety impacts without a shoulder, ities. They wanted to know the appropriate guardrail and curb Influence of asphalt concrete dikes and W-beam, to use for all speed and functional scenarios. Two states indi- Amount of allowable curb reveal to permit resurfacing cated they would also like guidance on the appropriate curb without resetting the curb, to be used with sidewalks. One state asked for guidelines for Placement of sand barrels behind the curb, and transitional sections (suburban to urban) of highway projects Curb trajectory information. in developing areas. One state wanted to address the need for additional lane widths for each configuration. Two states iden- tified the need for consideration of the practicalities of con- ADDITIONAL INFORMATION struction and maintenance in curbbarrier combinations. One of those two states had experienced problems with the com- The state that originated the problem statement has a unique binations when milling, paving, or removing snow. The other traversable curb (Type A6 in Figure 19) that it wanted to state had experienced problems placing guardrail in pave- be included in the study. The curb has a nominal width of ment when installing guardrail in front of the curb. 300 mm with a 13 slope across the top and no vertical reveal. Additionally, responding states also identified the follow- The curb is intended to permit pavement delineation and pro- ing voids: vide drainage control while minimizing the potential desta- bilization hazard to errant vehicles. To their knowledge, the Consideration of bumper height and vehicle center of curb had not been crash-tested. gravity, One state was interested in design, maintenance, and con- Drainage alternatives, struction issues concerning curbbarrier combinations. They