1、 ERRATA February 2012 Dear Customer: Recently, we were made aware of some technical revisions that need to be applied to the Roadside Design Guide, 4th Edition. Please replace the existing text with the corrected text to ensure that your edition is both accurate and current. AASHTO staff sincerely a
2、pologizes for any inconvenience. 2012 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Errata to Roadside Design Guide, 4th Edition RSDG-4-E4 1 February 2012 Page Existing Text Corrected Text 3-21 Example 3-D
3、does not have “Discussion” text to follow after the figure. Add the following text: “Discussion Since the critical foreslope is within the suggested clear-zone distance of 9 to 10.5 m 30 to 34 ft, it should be flattened if practical or considered for shielding. However, if this is an isolated obstac
4、le and the roadway has no significant crash history, it may be appropriate to do little more than delineate the drop-off in lieu of foreslope flattening or shielding.” 5-58 Figure 5-47 has partial text missing. Substitute Figure 5-47 with the attached revised figure. 6-2 Figure 6-1 shows incorrect m
5、etric and U.S. measurements for median widths. Substitute Figure 6-2 with the attached revised figure. 6-7 Figure 6-4 shows incorrect image of Brifen Wire Rope Safety Fence. Substitute Figure 6-7 with the attached revised figure. 8-31 In Table 8-7, text is missing from the FHWA Acceptance Level colu
6、mn (row 3). Add “CC89A” after CC89. 8-33 In Section 8.4.2.3.3, the last sentence reads: “The opposite direction crash test was not performed; therefore, until further testing is done, the HEART should be used only in locations with one-way traffic.” This sentence should read: “The HEART can be used
7、in bi-direction traffic provided the plastic side panels are lapped in the direction of traffic flow and an acceptable transition is used.” 8-48, 8-49 In Table 8-12, Sand Filled Barrels is placed in the wrong section. Substitute Table 8-12 with the attached revised table. 11-7 Figure 11-5 shows inco
8、rrect measurement of taper for LS. Substitute Figure 11-5 with the attached revised figure. G-1 Definition of Clear Zone reads: “The total roadside border area, starting at the edge of the traveled way, available for safe use by errant vehicles. This area may consist of a shoulder, a recoverable slo
9、pe, a non-recoverable slope, and/or a clear run-out area. The desired width is dependent upon the traffic volumes and speeds and on the roadside geometry.” The definition should read: “The unobstructed, traversable area provided beyond the edge of the through traveled way for the recovery of errant
10、vehicles. The clear zone includes shoulders, bike lanes, and auxiliary lanes, except those auxiliary lanes that function like through lanes.” 2012 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Roadside Topo
11、graphy and Drainage Features 3-21Through Traveled Way 7 m 23 ft 4 m 13 ft Runout Area 110 13.518DiscussionSince the non-recoverable foreslope is within the recommended suggested clear-zone distance of the 1V:10H foreslope, a runout area beyond the toe of the non-recoverable foreslope is desirable. U
12、sing the steepest recoverable foreslope before or after the non-recoverable foreslope, a clear-zone distance is selected from Table 3-1. In this example, the 1V:8H foreslope beyond the base of the fill dictates a 9 to 10 m 30 to 32 ft clear-zone distance. Since 7 m 23 ft are available at the top, an
13、 additional 2 to 3 m 7 to 10 ft could be provided at the bottom. Since this is less than the 3 m 10 ft recovery area that should be provided at the toe of all the non-recoverable slopes the 3 m 10 ft should be applied. All foreslope breaks may be rounded and no fixed objects would normally be built
14、within the upper or lower portions of the clear-zone or on the intervening foreslope.EXAMPLE 3-DDesign ADT: 12,000Design Speed: 110 km/h 70 mphSuggested clear-zone distance for 1V:6H foreslope: 9 to 10.5 m 30 to 34 ft (from Table 3-1)1611ThroughTraveled Way3 m 10 ft 4 m 13 ft 2 m 7 ftShoulderDiscuss
15、ionSince the critical foreslope is within the suggested clear-zone distance of 9 to 10.5 m 30 to 34 ft, it should be flattened if practical or considered for shielding. However, if this is an isolated obstacle and the roadway has no significant crash history, it may be appropriate to do little more
16、than delineate the drop-off in lieu of foreslope flattening or shielding. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Roadside Design Guide5-58Transition 1V:3H to 1V:6H1V:6HTraffic1.8 m (6) ShoulderL
17、R= 88 m (290)LC= 8.5 m (28)L2= 2.0 m (6.6)Figure 5-47. Example of Barrier Design for Non-Traversable EmbankmentsDiscussionThe area of concern begins at the top of the critical slope. This location is determined by reviewing the plan and cross-section details as well as any proposed grading that can
18、be done to eliminate or significantly reduce the length of the barrier, where appropriate. Because the purpose of a barrier installation is to reduce the likelihood of a vehicle from reaching a non-traversable ter-rain feature or fixed object, the designer may elect to shield more of the slope by se
19、lecting a larger clear zone distance. However, the benefit/cost issues of additional guardrail should be considered before increasing the guardrail length. It might be advantageous to review planned barrier lengths on site for proper length-of-need before installation. Refer to Chapter 8 for additio
20、nal grading details.The barrier may be terminated by anchoring it in a backslope or installing a crashworthy terminal. A buried-in-backslope terminal can shield the entire embankment area if the site grading is done appropriately. Before installing a buried-in-backslope terminal, the site layout and
21、 detailed review of the cross sections should be conducted. This will include consideration of ditch configurations, drainage requirements, and the configuration of the backslope.Based on the installation site conditions, it was determined that a parallel guard rail terminal be used. Note that the 1
22、5.2-m 50-ft end terminal was flared 300 mm 1 ft off the edge of shoulder to reduce nuisance hits.(5-8) Given: ADT = 650 vpd Speed = 100 km/h 60 mph Embankment slope = 1V:6H Horizontal curvature = 450 m 1,475 ft radius Select: Clear zone, LC = 5.0 to 5.5 m 16 to 18 ft (Table 3-1) (5.5 m 18 ft chosen
23、by designer)Adjustment factor for curvature = 1.4 (Table 3-2) Adjusted clear zone = (5.5) (1.4) = 7.7 m (18) (1.4) = 25 ft Runout length, LR= not applicable (see Discussion) Barrier offset, L2= 1.2 m 4 ft Flare rate: not applicable 2011 by the American Association of State Highway and Transportation
24、 Officials.All rights reserved. Duplication is a violation of applicable law.Roadside Design Guide6-2the repairs. Another concern associated with the installation of a median barrier is that it will limit the options of maintenance and emergency service vehicles to cross the median. In snowy climate
25、s, a median barrier also may affect the ability to store snow in the median. There may be other environmental impacts depending on the grading needed to install the barrier. For these reasons, a one-size-fits-all recommendation for the use of median barrier is not appropriate. Studies (7, 10) have s
26、hown that median barriers can significantly reduce the occurrence of cross-median crashes and the overall sever-ity of median-related crashes. With the potential to reduce high-severity crashes, it is recommended that median barriers be considered for high-speed, fully controlled-access roadways tha
27、t have traversable medians, as shown in Figure 6-1. 80706050403020100MEDIAN WIDTH (m)MEDIAN WIDTH (ft)0 5 10 15 20 80706050403020100AVERAGE DAILY TRAFFIC(Thousands)0 10 20 30 40 50 60 70(Thousands)AVERAGE DAILY TRAFFICBARRIERCONSIDEREDMEDIAN WIDTHWAYTRAVELEDSHOULDERWAYTRAVELEDBARRIEROPTIONALBARRIERO
28、PTIONALBARRIERCONSIDEREDBARRIERRECOMMENDEDBARRIERRECOMMENDEDFigure 6-1. Guidelines for Median Barriers on High-speed, Fully Controlled-Access RoadwaysFigure 6-1 shows recommended guidelines for the use of median barriers on high-speed, fully controlled-access roadways for loca-tions where the median
29、 is 9.1 m 30 ft in width or less and the average daily traffic (ADT) is greater than 20,000 vehicles per day (vpd). For locations with median widths less than 15.2 m 50 ft and where the ADT is less than 20,000 vpd, a median barrier is op-tional. However, the facility should be designed to facilitate
30、 future barrier placement if there are significant increases in ADT or a rise in the number of cross-median crashes occurs. For locations where median widths are greater than 9.1 m 30 ft but less than 15.2 m 50 ft and where the ADT is greater than 20,000 vpd, a cost/benefit analysis or an engineerin
31、g study may be conducted at the discre-tion of the transportation agency to determine the appropriate application for median barrier installations. The analysis should include the following factors in the evaluation: traffic volumes, vehicle classifications, median crossover history, crash incidents
32、, vertical and horizontal alignment relationships, and medianterrain configurations. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Median Barriers 6-7The high-tension systems also result in less damage
33、 to the barrier and, in many cases, the cables remain at the proper height after an impact that damages several posts. Although no manufacturer claims that their barrier remains functional in this condition, there may be a residual safety value under certain crash conditions. The posts can be instal
34、led in cast or driven sockets in the ground to facilitate removal and replacement. There are currently five high-tension cable barrier systems that have been accepted by FHWA as meeting NCHRP Report 350, Test Level (TL) 3 conditions. Modified versions of all five systems have been successfully teste
35、d at the NCHRP Report 350 Test Level 4 condition and approved for 1V:6H or flatter slopes.All of the systems also have been approved for limited use on 1V:4H slopes. Among the limitations is the fact that this configuration requires a TL-4 system that only functions at TL-3 because of the vehicle dy
36、namics inherent with steeper grades. The systems lateral placement within the median also is limited to no farther than 1.2 m (4 ft) down the 1V: 4H slope for adjacent traffic impacts and no closer than 2.7 m (9 ft) from the ditch bottom for opposite-side impacts.All of these systems use weak posts
37、to support the cables. However, they each utilize a unique post design. The following are the cur-rently accepted high-tension cable barrier systems: Brifen Wire Rope Safety FenceManufactured by Brifen USA, Inc., the Brifen system uses three or four cables. One is placed in a slot on the post while
38、the others intertwined between the posts (see Figure 6-4). The Cable Safety System (CASS)Manufactured by Trinity Industries, Inc., CASS uses three cables that are placed in a slot on the posts and separated by spacer blocks (see Figure 6-5). NU-CABLEManufactured by the Nucor Steel Marion Inc., the N
39、U-CABLE high-tension cable barrier system uses three or four cables attached to U-channel steel posts by unique hook bolts (see Figure 6-6). Blue Systems (Safence)The Safence system is a three or four-cable design. For a median barrier, all four cables are cen-tered within the top portion of slotted
40、 posts (see Figure 6-7). Gibraltar Cable Barrier SystemThe Gibraltar Cable Barrier System uses C-posts to support three or four cables. A steel hairpin and lock plate are used to attach the cables to the posts (see Figure 6-8).Figure 6-4. Brifen Wire Rope Safety Fence 2011 by the American Associatio
41、n of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.End Treatments (Anchorages, Terminals, and Crash Cushions) 8-318.4.2.3 Low-Maintenance and/or Self-Restoring Crash CushionsThe crash cushions shown in Table 8-7 typically are considered
42、for use at locations where a high frequency of impacts may be ex-pected. The category of “Low Maintenance and/or Self Restoring” crash cushions includes those devices that either suffer very little, if any, damage upon impact and are easily pulled back into their full operating condition, or they pa
43、rtially rebound after an impact and may only need an inspection to ensure that no parts have been damaged or misaligned. Although some attenuators can still function and save lives after being struck once, no device is completely maintenance free. It is important to note that devices in this categor
44、y may be low-maintenace, self-restoring, or both. Inclusion of a device in this combined category does not imply that the device has both attributes. Often these products are installed in high-speed, high-traffic volume ramps or medians to reduce the exposure of maintenance workers to the traffic.Ta
45、ble 8-7. Low-Maintenance and/or Self-Restoring Crash Cushions Crash Cushion Test LevelFHWA Acceptance LetterSystem DesignationManufacturerReference SectionCompressor 3 CC-95 Not Posted Traffix Devices 8.4.2.3.1EASI-CELL 1 CC-71 SCI 15Energy Absorption Systems, Inc.8.4.2.3.2Hybrid Energy Absorbing Re
46、usable Terminal (HEART)3CC-89 CC-89ANot PostedTrinity Highway Products, LLC8.4.2.3.3QuadGuard Elite7-bay unit8-bay unit9-bay unit233CC-57 CC-57ACC-57BSCT02eEnergy Absorption Systems, Inc.8.4.2.3.4QuadGuard LMC11-bay unit3 CC-43 SCT02fEnergy Absorption Systems, Inc.8.4.2.3.5Reusable Energy Absorbing
47、Crash Terminal (REACT 350)4-cylinder array9-cylinder array23CC-26,A-ICC-50,A-B, CC-73,A-CSCI16a-bEnergy Absorption Systems, Inc.8.4.2.3.6Smart Cushion Innovations (SCI)SCI-70GMSCI-100GM23CC-85 A and B SCI17a and b SCI Products, Inc. 8.4.2.3.78.4.2.3.1 Compressor AttenuatorThe Compressor Attenuator,
48、shown in Figure 8-31, is a proprietary, unidirectional, energy-absorbing crash cushion. It consists of high-density polyethylene (HDPE) attenuator modules designed to efficiently absorb energy in a relatively short distance. The modules are mounted on a proprietary UNI-BASE, which allows the unit to
49、 be installed quickly without the need for field assembly. The telescoping high-strength steel side panels redirect side impacts while protecting the absorbing modules from incidental damage. The unit is designed to take repeated impacts without any additional recovery procedures and with minimal or no repairs. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicat
