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FHWA Home / Safety / Local and Rural Road / W-beam Guardrail Repair Guide

A Guide for Highway and Street Maintenance Personnel

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November 2008

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1. Report No. FHWA FHWA-SA-08-002 2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle W-Beam Guardrail Repair: A Guide for Highway and Street Maintenance Personnel 5. Report Date August 2008
6. Performing Organization Code
7. Authors William J. Fitzgerald, P.E. 8. Performing Organization Report No.
9. Performing Organization Name and Address 10. Work Unit No.
Vanasse Hangen Brustlin Inc
8300 Boone Boulevard, Suite 700
Vienna, VA 22182-2626
PerformTech, Inc.
810 King Street
Alexandria, VA 22314
11. Contract or Grant No. DTFH61-05-D-00024
12. Sponsoring Agency Name and Address
Office of Safety
Federal Highway Administration
U.S. Department of Transportation
1200 New Jersey Avenue, S.E.
Washington, D.C. 20590
13. Type of Report and Period Covered Final Report
14. Sponsoring Agency Code
15. Supplementary Notes: The FHWA Office of Safety Contract Task Order Manager was Dr. Clayton Chen. The Technical Oversight Working Group included Ed Denehy-NYSDOT, Tom Nutini-Franklin Co, OH, Dennis Randolph-Calhoun Co, MI, Gary Rohrer-Washington Co, MD, and Glenn Schulte-UDOT.
16. Abstract Roadside barriers are a critical safety device as they shield motorist from what might be a more severe crash when leaving the roadway. Therefore, when damaged they need to be repaired so that they can perform this function. The purpose of this guide is to provide highway and maintenance personnel with up-to-date information on how to repair damaged W-Beam guardrail, the most frequently used barrier system. Three levels of damage are described and guidance is provided on the need and procedure for appropriate repairs. Appendices provide information on the resources (equipment, tools, crew, and time) that will be needed and forms for inspection and maintenance. This guide is an update of a document, W-Beam Guardrail Repair and Maintenance: A Guide for Local Highway and Street Maintenance Personnel, published in 1990 by FHWA.
17. Key Words W-Beam guardrail, repair, maintenance 18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page): Unclassified 21. No. of Pages: 53 22. Price

ACKNOWLEDGEMENTS

This guide was prepared by Vanasse Hangen Brustlin, Inc. (VHB) under FHWA Contract DTFH61-05-D-00024. Ms. Leslie Wright, Federal Highway Administration Office of Safety, was the initial Task Order Manager; she was replaced by Dr. Clayton Chen. The principal investigator and author was William J. Fitzgerald, P.E. as a consultant from PerformTech, Inc., to VHB. Technical editing was provided by Dr. Hugh McGee, P.E. and Ms. Vicki Glenn and document preparation was performed by Ms. Michelle Scism, all from VHB.

A Technical Working Oversight Group was formed to guide the preparation of this document. The members included:

TABLE OF CONTENTS

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I. INTRODUCTION: INTENT AND CONTENT

II. IDENTIFY PROBLEMS AND PLAN APPROPRIATE ACTION

ASSESS DAMAGE EXTENT AND REPAIR

STANDARD SECTION

TRANSITION SECTION

END TREATMENT SECTION

III. REPAIR SEQUENCE GUIDANCE

STANDARD AND TRANSITIONS SECTIONS

END TREATMENT SECTION

IV. REPAIR RECORD

REFERENCES

APPENDIX A: ESTIMATING RESOURCES FOR W-BEAM GUARDRAIL REPAIR

APPENDIX B: VIRGINIA DOT REPAIR GUIDANCE

APPENDIX C: MAINTENANCE GUIDANCE

APPENDIX D: DESCRIPTION OF CLEAR ZONE


I. INTRODUCTION: INTENT AND CONTENT

Ideally, highways should be designed so there is no need for roadside barriers; unfortunately, this is seldom practical. Bridge piers, steep side slopes, non-breakaway sign or luminaire (street light) posts, or other similar features along the road create potential dangers to drivers who leave the roadway. Because barriers themselves are potential hazards, use them only when necessary to shield a condition that could be significantly more hazardous. For example, crews may be able to modify a non-traversable, potentially dangerous drainage inlet to be safely traversable, making installation of a barrier unnecessary. Should the potential hazard be a steep embankment, a bridge pier, or a large sign support, installing a barrier may be the best option for preventing serious injury or fatality.

Deciding whether to install barrier can be a complex decision. Guidance on when and where to install a barrier can be found in the Roadside Design Guide (see reference list). However, once a barrier is installed, road crews must maintain it and repair it to ensure it functions as intended.

Strong post W-beam guardrail with wood block and metal post.

Strong post W-beam guardrail with wood block and metal post.

This guide focuses on how to repair (not design) the most widely used barrier–the strong post W-beam guardrail identified as SGR-04 in the Standardized Highway Barrier Hardware Guide. (The term guardrail, and in some states guiderail, is commonly used either for just W-beam barriers or for barriers in general; for future use in this guide, the term W-beam guardrail will refer to the strong post W-beam barrier system.) The standard strong post W-beam guardrail consists of a W-beam rail element and strong posts (wood or steel) spaced at 6 ft3 in with the rail blocked out from the posts. Although the focus is the strong post system, much of the guidance that is provided for the repair of the strong post design can apply to the weak post design as well.

This guide is structured around the three sections of a guardrail that have variations in design to serve their purposes:

Diagram
Standard sections of roadside barriers.
(Source: Roadside Design Guide)

The next chapter identifies three levels of damage resulting from impacts into each section and suggests corrective action. Chapter III provides basic guidance on repair sequence and Chapter IV discusses record keeping. Appendix A addresses estimating parts and materials and identifying resources (work crews and equipment) needed for typical repair work and includes two examples of damage inspection reports and a tool for estimating the radius of curved guardrail elements. Appendix B provides one State's guardrail repair guidelines. Although this guide is for guardrail repair, Appendix C provides guidance for maintenance activities that improve the likelihood that barriers of all types will perform as intended. Finally, Appendix D provides a description of the clear zone, an important safety feature for all roads. References are found after Chapter IV.

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II. IDENTIFY PROBLEMS AND PLAN APPROPRIATE ACTION

Road agencies can learn of damaged guardrail from several sources, an accident report is the most obvious. However, as many guardrail impacts are drive-away situations, maintenance (or other highway) personnel can identify damage that may not be obvious to the casual observer, but that could keep the guardrail from performing as intended. Once the agency receives notice of damage, make an on-site review of the damage. The first priority of a review is to determine whether the barrier can be removed — by eliminating the hazard it was intended to shield. This is seldom an option, but do not lose the opportunity to improve the roadside safety. If the barrier is to remain, then the review objective is to determine the extent of the damage, what repairs to make, and when to make them.

Three categories of functionality can be used to describe the extent of damage:

  1. Guardrail is no longer reasonably functional.
  2. Guardrail should function adequately under a majority of impacts.
  3. Damage should not affect the guardrail's ability to perform.

Each agency must make a risk assessment about the timing of repair for each different category of functionality. The assessment would include, among other factors, agency resources (within its overall mission), hazard exposure (how likely is it the guardrail will be hit again), and hazard severity. It is important that each agency develop guidance for when to make repairs.

ASSESS DAMAGE EXTENT AND REPAIR

2. Photo. This photo shows drums placed next to a damaged guardrail section. Drums, as shown, vertical panels, or cones, can be used to warn drivers of the damaged guardrail until it can be repaired.

Upon arriving at the site, clear any debris from the traffic lanes and shoulders. Place debris that cannot be hauled away at least 3 ft behind still-effective guardrail. When the damage leaves the guardrail nonfunctional, and it cannot be repaired immediately, warn traffic of the hazard by putting out temporary warning devices, such as drums, vertical panels, cones, or other devices, in accordance with the Manual on Uniform Traffic Control Devices (MUTCD), Part 6, Temporary Traffic Control, or local policy.

If a blunt end remains, take steps to minimize its danger. Crews could drop the rail forming a turndown; while not desirable, it is better than leaving a spear. In extremely dangerous situations, use a truck-mounted attenuator (TMA) or other type of attenuator. If possible, smooth any rough grading caused by the impact. Make a damage inspection report detailed enough to estimate repair parts and resources needed. Appendix A provides a sample damage inspection report (Item 1); provides information on estimating parts and materials (Item 2), equipment and tools (Item 3), time needed (Item 4), and crew size (Item 5); and a sample repair log (Item 6).

For each of the three sections of the W-beam guardrail system, the following is provided: the function of the section, examples of extent of damage, proper repair techniques, and a checklist for repairs.

STANDARD SECTION

The function of the standard W-beam section is to prevent penetration by a vehicle, either through, over, or under the W-beam and to smoothly redirect the vehicle. You can use the chart below to determine the functionality category based upon the damage to the standard section of the W-beam guardrail.

STANDARD SECTION OF W-BEAM
EXTENT OF DAMAGE FUNCTIONALITY

RAIL ELEMENT SEPARATED

1

RAIL ELEMENT TORN 1
TOP OF RAIL HEIGHT ≤ 24" 1

RAIL ELEMENTS INTACT

FULL SPLICES

TOP OF RAIL HEIGHT > 24"*

AMOUNT OUT OF ALIGNMENT AMOUNT OF BROKEN/BENT OR SEPARATED POSTS 3

<6"

0
1-2 2
≥3 1
6" – 12" 0-2 2
≥3 1
≥18" NOT APPLICABLE 1

FUNCTIONALITY CATEGORIES:

1 Guardrail no longer reasonably functional

2 Guardrail should function adequately under a majority of impacts

3 Should not impair the guardrail's ability to perform

In narrative format, this chart shows: Functionality category 1 applies to any damage where the rail element is separated or torn, or the rail height is equal to or less than 24 inches. Category 1 also applies even if none of these three conditions exist, but (1) there are three or more broken, bent, or separated posts and the amount out of alignment is 12 inches or less, or (2) if the amount out of alignment is equal to or greater than 18 inches regardless of any broken, bent or separated posts. Functionality category 2 applies if the guardrail is out of alignment no more than 12 inches and no more than two broken, bent, or separated posts. Functionality category 3 applies only if the guardrail has no damage other than being out of alignment by less than 6 inches.

Damage Examples

1. Damage: Guardrail no longer reasonably functional.

Photo. This photo shows a guardrail which is bent out of line by more than 18 inches.

Rail is bent/pushed more than 18 inches out of line, and/or became less than 24 inches high, or three or more posts are broken/bent over and separated from the rail.*

2. Damage: Guardrail should function adequately under a majority of impacts.

Photo. This photo shows a guardrail which is bent less than 12 inches out of line.

Rail is bent/pushed out of line less than 12 inches – rail element is intact (no tears and full splices).*

7. Photo. This photo shows a guardrail with two broked posts.

One or two posts are broken/bent over and separated from the rail – rail element is intact (no tears and full splices).*


3. Damage: Should not impair the guardrail's ability to perform.

Photo. This photo shows a guardrail which is bent less than 6 inches.

Rail is bent/pushed out of line less than 6 inches – rail element is intact (no tears and full splices; guardrail height is minimum 26-inches).*

*This is the best guidance currently available. An NCHRP study is under way to determine the level of damage that should not affect barrier functionality.

Properly Repaired Standard Section

The primary mechanism enabling guardrail to redirect a vehicle is tension developed in the rail element. Therefore, all repairs must ensure that full-tension capability is reestablished. The strong posts contribute to smooth redirection by limiting the amount of deflection and providing consistent stiffness along the rail to prevent pocketing. Repair all posts to a condition enabling them to perform their function.

A second critical element of functional W-beam is proper height. Full-scale tests show that 25-in-high W-beam (measured to the top of the rail element) will not contain a design impact (a 4,400-lb pick-up truck at 62 mi/h and a 25° impact angle).

If the length of damaged W-beam is significant, then repair the barrier to meet the current standard for height. For short sections (one or two panels) of repair, it generally is not practical to adjust the current height. When the whole run of the W-beam guardrail is substantially (3 inches or more) below the current standard (and is not repaired at this time), report the situation to management to ensure it is included in future W-beam upgrade projects.

Ensure all repaired guardrail meets your agency's current standard (except related to height, as discussed above). For repair only, use posts of a material different than the existing material only when it is impractical to obtain like-material posts. The length of W-beam to be repaired should depend on the total length of barrier and the extent of damage. If damage is severe and either the length of the whole installation is short or the amount of damage is greater than a certain percent of the total length, then bring the total system to current agency standard (including height). Values for these two criteria are arbitrary and should be set by the agency. Appendix B provides an example of one State's criteria (Note: the height criteria included in this example do not conform to the guidance in this booklet). Typical values are 100 to 200 ftto define short length and 50 percent to define portion of total length needing repair.

There is an exception to the recommendation in the previous paragraph to meet current agency standards: When existing steel post/steel block out W-beam needs repair, and it is not against agency policy, crews can use (or install) steel blocks when the posted speed is 45 mi/h or less. Back-up plates (1-ft-long pieces of W-beam rail) are required at nonsplice rail-to-post connections, and there should be no washers under any rail-to-post bolt head.

Repaired W-beam Checklist

  1. Tension capability is intact:
    • No tears.
    • Eight ⅝-in splice bolts in each rail connection.
    • No rail subjected to a cutting torch is reused; any new holes are drilled.
  2. Height is according to standard.
  3. Posts are intact and firmly bedded in ground. Use a longer post (7 ft+) in front of a fill slope when there is less than 1 ftof relatively flat ground behind the post.
  4. No washers under rail-to-post bolt head.
  5. Available deflection distance in back of W-beam to a rigid vertical object (W-beam deflects as it develops tension – 3 ftis the standard distance provided; if 3 ftis not available, then add posts and/or nest rail to stiffen the system).
  6. Lap rail elements in the direction of traffic (upstream {approach} rail is in front of downstream {leave} rail).
  7. For wood block on wood posts, use toenails to restrain blocks from rotating, preferably one on each side of the block, 2 inches from the top or bottom.
  8. Guardrail-mounted delineators in damaged section replaced. If no guardrail-mounted delineators previously existed, install delineators per MUTCD and/or highway agency policy.

(Items 3 and 5 are most applicable for high-speed facilities and could be less restrictive for lower speed facilities.)

TRANSITION SECTION

The function of the transition section is to gradually and smoothly stiffen a semi-flexible W-beam section having a 3-ftdynamic deflection as it attaches to a rigid, non-deflecting object such as a concrete bridge parapet or (anchored) concrete barrier to prevent pocketing.

Damage Examples

1. Damage: Transition no longer reasonably functional.

Photo. This photo shows a guardrail which is not attached to the ridgid object immediately after it.

W-beam element is not attached to rigid object.

Photo. This photo shows a guardrail which is extermemly bent in advance of a rigid object.

W-beam is severely pocketed in advance of the rigid object.


2. Damage: Transition should function adequately under a majority of impacts.

Photo. Flattened Rail

Rail is flattened and bent/pushed out of line less than 12 inches; rail element is intact and securely attached to the rigid object.

3. Damage: Should not impair the transition's ability to perform.

Photo. This photo shows a traditional transition from a guardrail to a bridge parapet.

Rail is flattened / pushed out of line less than 6 inches; rail element is intact and securely attached to the rigid object.

Properly Repaired Transition Sections

The traditional transition to concrete bridge parapets constructed before the 1990s used 3-ft, 1½-in post spacing for 25 ft in advance of the connection to the rigid object. When tested at a high speed, this design failed miserably.

Many designs meet the current testing requirements for high-speed facilities; for low speed facilities, the Texas DOT has developed a more economical[1]. All accepted transition designs incorporate four features:

Photo. This photo shows a traditional transition from a guardrail to a bridge parapet. Traditional transition.

The whole treatment is typically 25 ft long but could be 18½ or 31½ ft. Although metal bridge railings may not be as rigid as concrete parapets, follow the same concept of a strong tension connection, gradual stiffening, and snag prevention.

Repair transitions that did not previously contain all the above features to current standards; if that is not practical, then provide the above features on high-type facilities. (A rail-to-post bolt is not required at the locations of any extra posts when an installation is not to a standard.) On lower type facilities, it may not be practical to include all of the features to their full extent, but all repairs should have a strong tension connection. Repairs should be conducted to correct the connection even if a transition is outside the normal limits of repair within a W-beam run or if it does not contain a strong tension connection.

Repaired Transition Checklist

  1. Tension capability is intact:
    Photo. This photo shows a transition from a guardrail to a bridge parapet. The bolt heads are circled to highlight protrusion.
    1. a. No tears in rail elements.
    2. Minimum of four ⅞-in-high strength bolts/threaded rods in connection to rigid object – ensure the bolt heads or nuts on the threaded rods protrude no more than ¾ inches from the face of the connection plate.
    3. All splices are intact (eight splice bolts in each rail connection)
    4. No rail subjected to a cutting torch.
  2. Extra/larger posts – the last post spacing in advance of the rigid object should be 1 ft, 6¾ in.
  3. Nested last rail element.
  4. Rub rail or curb to prevent wheel snagging.
  5. Bridge shoe lapped in the direction of the near-side traffic.
  6. Damaged or knocked down object (hazard) marker (if any) replaced on or adjacent to bridge parapet.

END TREATMENT SECTION

The function of the end treatment is to prevent serious injury to occupant when struck on the end and provide tension for the W-beam for side (traffic face) impacts.

Over the years end treatments have developed from simply ending the W-beam run (probably with a "shovel" end section attached – with or without the end section, providing little tension but most importantly presenting a spear) to turn down systems (that provide tension and won't spear, but that could launch a vehicle) to stand-up "safe" end treatments. The two major types of stand-up end treatments are non-energy-absorbing and energy-absorbing.

Photo. This photo shows a non-energy-absorbing end treatment.

Non-energy-absorbing end treatment.

Photo. This photo shows an energy-absorbing head that has come off of the rail.

Energy-absorbing end treatment.


End treatments prevent serious injury either by being relatively soft for end-on impacts or using an energy-absorbing head slipped over the rail element to absorb the energy of the impacting vehicle by deforming the rail as it is forced into the head during shallow-angle, end-on impacts. For the stand-up end treatments, the tension function is provided by a cable attached to the rail element and anchored in the first post through a bearing plate and the post is placed in a foundation. Since the early 1990s, a strut ties post 1 together to post 2 to provide the needed resistance to the tension in the cable developed from a downstream impact.

Damage Examples

1. Damage: End treatment no longer reasonably functional.

Photo. This photo shows a partially destroyed energy absorbing end treatment.

End treatment partially or fully destroyed and presents a blunt end Energy-absorbing system

End treatment partially or fully destroyed and presents a blunt end Non-energy-absorbing system

End treatment partially or fully destroyed and presents a blunt end Non-energy-absorbing system



Energy-absorbing head off of rail- probably will not ride down rail but may create a spear.

Energy-absorbing head off of rail– probably will not ride down rail but may create a spear.

Energy-absorbing end treatments depend on the column strength of the rail element to activate the energy-absorbing characteristic of the design. The rail element must be in a straight line to develop this strength. If there are dents in the rail element, even relatively small, near the impact head, then the system will probably not perform as desired for shallow-angle, end-on impacts. Replace the dented rail element.

2. Damage: End treatment should function adequately under a majority of impacts.

Photo. This photo shows an end treatment that is on a rail with a broken first post.

Post 1 is broken such that full tension is not developed for downstream hits; however, the impact head should absorb most of a vehicle's energy for shallow–angle, end-on impacts.

Neither the turndown nor the breakaway cable terminal (BCT) (see photos on the below) have been successfully crash tested for both a large vehicle (sedan or pick-up) and a small car. One should replace them with current standard hardware, even for minor damage. This is especially true for high-type facilities. Turndowns are easy to identify. The BCT looks similar to a MELT (Modified Eccentric Loader Terminal, see photo below), a stand-up end treatment that passed previous crash-test requirements and can be repaired when it incurs minor damage. The BCT has no strut between posts 1 and 2, standard strong posts for all posts beyond post 2, and bolts attaching the rail element to all posts.

Photo. This photo shows a turned down end treatment where the guardrail is turned down and burried in the ground.

Turndown is obvious.

Photo. This photo shows a breakaway cable terminal.

Breakaway Cable Terminal (BCT) No strut between posts 1 and 2. Standard posts beyond post 2. Bolts attach rail to each post.



Photo. This photo shows a Modified Eccentric Loader Terminal.

Modified Eccentric Loader Terminal (MELT) Strut between posts 1 and 2. All weak posts within system. No rail-to-post bolts except at post 1.

3. Damage: Should not impair the end treatment's ability to perform.

Photo. This photo shows rail element that is less than 12 inches out of line.

Post 1 is intact. Rail element is less than 12 inches out of line (non-energy-absorbing end treatment only).

Properly Repaired/Replaced End Treatment

For a W-beam guardrail to adequately shield a serious hazard, the length of the W-beam guardrail must extend some distance upstream in advance of the hazard. If the W-beam guardrail is not long enough, then a vehicle can leave the roadway before it is beside the hazard and still reach the hazard the W-beam was intended to shield. This adequate distance in advance of the hazard is called the length of need (LON). Although a designer uses a special procedure to determine the LON, a simple field expedient procedure, shown in the sketch below, is to multiply the distance between the front of the W-beam and the back of the hazard (D-D1) by 15. If the back of the hazard is greater than 30 ft from the edge of the travel lane (EOTL) on a high-speed road, then 30 ft is a reasonable value for D. For lower speed roads, use a value of 18 ft (or the roadway's design clear zone[2] value, if known) instead of 30 ft.

Diagram. Field Length of Need. d

The best end treatment is probably a properly constructed buried-in-backslope (BIB) end treatment. It provides full tension for the W-beam and eliminates the possibility of injury due to hitting the end since the end is buried. When a natural backslope is near where the agency plans to completely replace a damaged end treatment, a good option is to use a BIB for the repair (conditioned that no access is required behind the W-beam at this point).

Photo. This photo shows a burried-in-backslope end treatment.
Photo. This photo shows another burried-in-backslope end treatment.

Examples of buried-in-backslope end treatments.

When repairing or replacing a stand-up end treatment with a new stand-up end treatment, you should provide the LON. However, in the majority of situations, it is either unavailable or impractical to provide the LON. Although the non-energy-absorbing end treatments perform well to minimize the hazard of the end of the W-beam, their softness allows the vehicle to pass through and behind the guardrail, and without adequate LON, could reach the hazard the W-beam was intended to shield. An energy-absorbing end treatment has an additional capability beyond developing tension and not causing serious injury on end-on impact: for shallow-angle, end-on hits, it can absorb much of the vehicle's energy and either stop the vehicle within the system itself or slow the vehicle significantly such that any downstream impact should be less severe. Therefore, use energy-absorbing systems to repair or upgrade damaged end treatments if they do not have acceptable LON and satisfactory grading, as discussed below.

Many current crashworthy end treatments are proprietary and have been designed and engineered with unique details necessary to allow them to perform properly. For example, some posts in the installations have bolts connecting the rail to the post while others do not. Also, most designs have evolved to make them more effective as well as more economically competitive. Therefore, before beginning repair on these systems, or installing new as replacements, be sure you have the manufacturer's shop drawings and installation manual for the particular model on site.

Grading: All accepted end terminals (except the BIB) were tested on flat ground. Therefore, it is best to duplicate this condition in the field so the end treatment has the best chance of performing as intended. This is generally accepted as being provided when there is 5 ft of relatively flat ground (IV:10H or flatter) behind the first post of the system (and gradually tapered back to the existing cross section in advance of the end treatment), as shown below.

Diagram. This diagram shows the recommented roadside grading plan from the Roadside Design Guide.
Recommended Grading Plan.
Source: Roadside Design Guide

The grading downstream of the end treatment should be available clear zone in accordance with the LON concept describe above. Also, because the posts of the system are designed to break off or bend upon end-on hits to allow the vehicle to continue down or through the system, ensure whatever posts remain after breaking or bending extend no more than 4 inches above the ground.

The previous recommendation to use energy-absorbing end treatments is re-emphasized because the 5 ft flat grading is seldom achievable in the field.

Photo. This shows a photo of a Vermont End Terminal.

Guidelines for the Selection of W-beam Barrier Terminals developed by FHWA, provides additional information on the selection and performance of the different currently accepted end treatments. The CD-ROM (Publication Number FHWA-SA-06-19) containing these guidelines can be obtained from the FHWA Report Center. Fax requests to (301) 577-1421 or email requests to report.center@fhwa.dot.gov.

The Vermont End Terminal is a relatively inexpensive end treatment that provides both tension and a "safe" impact for lower speed (≤ 45 mph) facilities: (Additional information on this end treatment is available in the AASHTO Roadside Design Guide (RDG), chapter 8). Its use is also appropriate on a higher speed facility at the approach to a STOP sign. It uses a typical cable to develop the required tension and a radius W-beam element to prevent spearing. It is also fairly easy to construct.

When an end treatment's only function is to develop tension, such as when used at the downstream end of a run of barrier (that is outside the clear zone of opposing traffic), an economical system is to simply attach the typical cable to the last rail element and anchor the cable in the last post that uses a steel foundation tube for resistance (see photo and figure on following page).

Photo. This photo shows the back side of a an anchored end treatment so that the cable is seen.

Diagram. This diagram shows the parts of a typical W-Beam Anchor.

Repaired/Replaced End Treatment Checklist:

  1. Use no interchanged parts from different manufacture's systems for parts unique to the particular end treatment being repaired.
  2. For energy-absorbing systems, place the head completely onto the rail element.
  3. For energy-absorbing systems, the cable anchorage to the rail element allows the cable to release from the rail if the head slides.
  4. Post 1's top part will separate from its foundation for end-on impacts.
  5. Replace any damaged posts within the end treatment that were originally breakaway or yielding posts with breakaway or yielding posts approved by the system's manufacturer.
  6. Grading provides no more than 4 inches above ground to the strut or to what will remain as a stub.
  7. Bearing plate is properly oriented.
  8. Cable is tightened to a taut condition; cannot lift up on the cable more than 1 inch.
  9. Retroreflective object (hazard) marker in place on non-buried end treatments per highway agency policy.

III. REPAIR SEQUENCE GUIDANCE

This chapter provides guidance on how to repair W-beam guardrail sections. Some critical actions you should take before the actual repair include:

The remaining portion of this chapter is divided into standard and transition sections, and end treatments

STANDARD AND TRANSITIONS SECTIONS

The following sequence is usually followed in repairing the standard or transition sections:

  1. Disassemble damaged guardrail.
    1. Spray the connecting bolts with penetrating oil for easier removal. Unbolt the damaged rail-beam sections.
    2. If the elliptical shoulder is worn off the bolt, then hold the smooth round head with vise grips to unscrew the nut. Use a torch to cut stubborn bolts. Do not torch cut rail sections to be reused.
  2. Pull out damaged posts.
    1. Steel posts can often be worked out by hand or with a crowbar. Crews may have to use a chain and hoist to dig or pull wood posts.
    2. Slightly twisted steel posts still firmly in the ground can often be straightened in place by pulling with a chain attached to a truck. Provide traffic control warning if the truck's operation encroaches on the traveled roadway. Use a crowbar to pull posts only pushed off-line back into line.
  3. If necessary, use a grader to reshape the shoulder area and recompact the soil for posts. If placing new post(s), then rework the area before installing the post(s), if practical.
  4. Set up a stringline to position posts at the proper height, alignment, and spacing. If repairing more than two panels, then set the W-beam to the standard height. It is relatively easy to create up to a 4-in change in height over one panel length. (When the rail height is not adjusted and is 3 or more inches below standard, report it to your maintenance supervisor.) Mark the stringline for the proper post height and alignment. Use a tape or a measuring stick to mark the proper post spacing.
  5. Drill or dig holes for the posts, if necessary.
    This diagram shows the splic lap detail. The upstream rail section overlaps the downstream section.
  6. Set or drive posts to the proper height.
  7. Backfill and compact the soil around the posts.
  8. Check post alignment and height. Correct any major deviations.
  9. Starting downstream and working backwards, loosely hang new rail sections and offset blocks. Lap rail elements in the direction of traffic. In general, do not use washers under the bolt heads of the rail-to-post bolts. When using steel posts with steel offset blocks, a back-up plate is needed at the intermediate posts (the posts between the rail splices).
  10. If necessary, use a drift pin to line up the holes for bolting.
  11. Make sure all 8 bolts are in place in each splice connection.
  12. Leave all connections finger tight to allow for lengthwise adjustment after all sections are installed.
  13. Final assembly – when all rail is hung, go back and snugly tighten all bolts. There is no need to overtighten.
  14. Cleanup – smooth out the shoulder and slope approaching the guardrail so the next vehicle to run into it has a smooth path.
  15. Install guardrail-mounted delineators and, if appropriate, object hazard markers.

Make a final inspection before leaving the site. Complete the suggested checklist at each location to document the work.

Completed Work Inspection Checklist
(Standard Section and Transitions)

  • ____Do all splices have eight bolts; have all bolts–both splice and rail–to–post–been checked to see that each is tightened snug?
  • ____Is a blockout used on each post?
  • ____Guardrail height was checked to make sure it is correct and did not shift up or down out of tolerance during the final assembly?
  • ____Deflection distance is provided from any vertical, rigid object or the W-beam system appropriately stiffened?
  • ____Adequate soil backing is provided behind the posts; if not, are longer posts used?
  • ____ A nail(s) is driven in each wood blockout on wood posts to toenail the block to the post to prevent rotation?
  • ____ If steel blockouts are retained, does each steel post between the splices have a back-up plate behind the rail element?
  • ____ Were all washers between the bolt head and the rail element removed (unless required) from the repaired W-beam length?
  • ____ Is the lap of the rail elements correct?
  • ____ Are guardrail-mounted delineators located properly on the guardrail?
  • For repair including transitions:
  • ____ Are the four (minimum) ⅞-inch-high strength bolts properly anchored and NOT protruding significantly in front?
  • ____ Is the last rail element nested?
  • ____ Are there enough/properly sized posts adjacent to the rigid object?
  • ____ Has a means to prevent wheel snagging (rub rail or curbing) been applied, if necessary?
  • ____ Is the lap of the bridge shoe correct?

Date repair completed: _________________________

Repair completion inspected by:______________________________ (Signed)

END TREATMENT SECTION

The following steps are suggested for end treatments:

  1. Remove the damaged hardware as described for the standard W-beam section. If the end treatment is an energy-absorbing type, and the impact head is pushed down the rail element, cut off the deformed steel and pull off the head – do not cut the rail or unbolt the splice downstream of the head until the head is removed. Guidance for determining whether an impacted head can be reused: Reuse it when there is obviously no damage; replace it if questionable.
  2. For damage meeting criteria that requires replacing the whole end treatment, check the LON to determine if appropriate W-beam length is available to adequately shield the hazard. Add any standard W-beam as deemed necessary before installing the new end treatment. Provide the necessary grading platform prior to constructing any end treatments.

Because of the many possible options that repair/replace damaged end treatments, it is virtually impossible to give detailed instructions for their treatment. However, two items must be discussed.

Many different types of posts are used in the different end treatments, both generic and proprietary. Examples are:

Because of this variety, make a detailed inspection of the type in the existing installation. Replace damaged posts in an installation that is only to be partially repaired with the same type of the original posts. However, several manufacturers have developed steel posts that facilitate repair – be sure to check with each manufacturer for approved variations and mixing of post types before using a post type different than the damaged one(s).

To repair or replace any proprietary types of end treatments, it is imperative that crews have the manufacturer's shop drawings and installation manual on site during repairs. Installation manuals also contain guidance for repairing damaged installations and can be used on generic installations as well, such as removing the wood stub left in a foundation tube.

Completed Work Inspection Checklist (End Treatments)

  • ___Is the anchor cable properly attached to the rail element?
  • ____Is the grading correct under the appropriate standard (including 4-in stub height requirement for post foundations and for struts)?
  • ____ Will post 1 separate from its base on end-on impacts?
  • ____ Has the LON been reviewed for appropriateness?
  • ____ For energy-absorbing end treatments, is the rail element inserted deeply inside the head, and is there NO bolt connecting the rail to post 1?
  • ____ Is the bearing plate properly oriented and restrained from turning?
  • ____ Are all rail-to-post bolts located according to the manufacturer's drawings?
  • ____ Is the anchor cable taut?
  • ____ Are all wood block-outs on wood posts properly toenailed to prevent rotation?
  • ____ Is the object (hazard) marker installed?

Date repair completed: _________________________

Repair completion inspected by: ______________________________(Signed)

IV. REPAIR RECORD

All agencies should maintain work records of maintenance performed. If your agency has an existing system for keeping track of maintenance work, then use it to record work to repair the guardrail, record the parts used, when the repair was made, and verify that work was checked for correctness.

If your agency does not have a complete record system, then consider the following suggestions:

REFERENCES

  1. Manual on Uniform Traffic Control Devices (MUTCD):
    http://mutcd.fhwa.dot.gov/
  2. Standardized Highway Barrier Hardware Guide:
    http://aashtotf13.tamu.edu/
  3. FHWA-accepted roadside hardware:
    http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/
  4. End-treatment manufacturers:
    Road Systems Inc: http://www.roadsystems.com/
    Trinity Industries: http://www.highwayguardrail.com/
  5. AASHTO Roadside Design Guide:
    https://bookstore.transportation.org/item_details.aspx?id=1172
  6. Guidelines for the Selection of W-beam Barrier Terminals: FHWA Publication FHWA-SA-06-19, December 2006 (available from FHWA Report Center; request by email at Report.Center@fhwa.dot.gov)

APPENDIX A: ESTIMATING RESOURCES FOR W-BEAM GUARDRAIL REPAIR

1. EXAMPLE OF DAMAGE INSPECTION REPORT

Damage inspection Report – New York State DOT

Damage Inspection Report - New York State DOT


Calculating Guardrail Radius (to complete form above)

Traffice Face Convex
Diagram. This diagram shows where to acquire the measurements to calculate radius.

Table. This table shows the functions of a 12-foot, 6-inch circular arc.

2. ESTIMATING PARTS AND MATERIALS FOR STANDARD SECTION W-BEAM REPAIR

Typical elements of the W-beam guardrail (a standard 12-ft, 6-in rail length is assumed; if an agency allows a 25-ft rail length, then make appropriate adjustments) include the following:

Diagram. This diagram shows how to mount w-beam rail to wood posts with wood offset blocks.

Arrow pointing to the leftTraffic


W-Beam with Wood Offset Block on Wood Post

Diagram. This diagram shows how to mount w-beam rail to steel posts with approved offset blocks.

Arrow pointing to the leftTraffic


W-Beam with Approved Offset Block on Steel Post

Diagram. This diagram shows how to mount w-beam rail to steel posts with steel offset blocks.

Arrow pointing to the leftTraffic

W-Beam with Steel Offset Block on Steel Post


Checklist of Materials for Repair
Item Compute Number needed

W-beam galvanized steel rail sections

12-ft, 6-in-long, desirably punched @ 3ft, 1½ -in spacing

Tally # of damaged

Sections @ 12ft, 6 in

 

⅝-in by 1¼ -in-long splice bolts with nuts

(# sections x 8) + 8

 

⅝–in rail-to-post bolts with recess nuts and round washers for connecting rail to post and block

(# sections x 2) + 1

 

6-ft , 0-in posts*

(# sections x 2) + 1

 

Offset blocks

Same as # of posts

 

For wood block on wood post:

10 16d galvanized nails
(preferably two per offset block)

2 x # of offset blocks

 

For steel block on steel post:

12-in W-beam back-up plate

Same as # of sections

 

For steel block on steel post:

⅝ -in by 1½ -in hex-head bolts to connect block

2 x # of offset blocks

 

Guardrail-mounted delineators

Same as # of sections

 

Object (hazard) markers

1 for each end

 

* If there is not adequate soil support behind the posts, use 7 ft or longer posts.

This list indicates an exact number of parts. Be sure to take into account additional numbers of each part for damage, loss, etc.

A detailed list like this is not appropriate for end-treatment repair/replacement. The proprietary manufacturers' installation manuals contain bills of material for each model of their products. Check these when conducting a complete replacement installation or for the appropriate quantities based on the amount of repair/replacement.

3. ESTIMATING EQUIPMENT AND TOOLS

The following is a listing of equipment and tools that will be needed for guardrail repair. There are two lists: the first is from a typical state highway agency truck; and the second is from a typical guardrail contractor truck. Make sure you comply with OSHA or your local regulations when using this equipment.

EXAMPLE 1– A TYPICAL STATE HIGHWAY AGENCY TRUCK

Supervisor Truck Supplies

⅜-in drive ratchet and socket set (end treatments have small nuts and bolts)

¾-in drive ratchet and socket set (bridge connections and anchor terminals)

½-in drive ratchet and socket set with 3-in and 10-in extensions

7/16 to 1⅛" sockets

5 to 1¼" bell sockets

4-in to ½-in drive sockets

Four - splice pins, 2 pinch bars / pry bars

Open end and box wrench set 5/16 to 1¼ inch

Two ½-in impact wrench

Two 5/16-in impact sockets

Two 1⅛-in impact socket

Three 1¼-in impact bell socket

Two 1¼-in Impact Deep Bell Socket

One 15-in adjustable wrench

One 20-in adjustable wrench

Four vise grip pliers

Two 4-lb hammers

One 18 lb sledge hammer

One 10-lb sledge hammer

Two flat shovels

Two round shovels

Two post hole digger

Two digging bars

One post puller

Cut-off saw, extra blades

Chain saw, bar oil

Mix oil for saws

2- or 3-gal mix gas can

2 5-gal gas cans

Hilti concrete drill set

Hilti ½, ⅝, ⅞, 1-in bits

3 7/8–inch-hole saws

Epoxy

Long heavy-duty jumper cables

Ink markers

Acetylene torch set

Two chisels

3500-watt generator

Two 100-ft electric cords

Two1/2-in VSR drills

Two 1-in step bits

Paint & cold galvanizer

Penetrating oil / spray

Two- Line levels

String line

Line pins

200-ft steel tape

G/R Standards and Specifications

Construction Log Book

Accident Investigation Reports

Two Pull binders

Maintenance of Traffic Standards

Work zone signs & stands

STOP / SLOW paddles

Cones

Hard hats, safety vests, safety glasses, gloves,
hearing protection, dust masks

MSDS Manual, Hazard Communication, Safety Manuals

First-aid kit

Blood-Born Pathogen Kit

First-Aid Reports

Wasp and bee spray

5-gal water cooler

Quantity sheets

Respirators

Camera

Clipboard

Timesheets

Cell phone

Credit cards

Guardrail-mounted delineators

Object Markers

Post Pounder Truck / Rail Truck

Add to Supervisor Truck Supplies:

Truck-mounted post pounder – holds 30 posts – grease gun

Air compressor, 92 CFM

Two air hoses

Hydraulic cylinder (pulling)

Three chains

Canvas strap for lifting

One 60-lb jack hammer

Two vehicle battery chargers

Two Dewalt 18-volt wrenches

 

EXAMPLE 2– A TYPICAL GUARDRAIL CONTRACTOR REPAIR TRUCK

Foreman Truck Supplies

⅜-in drive ratchet and socket set (end treatments have small nuts and bolts)

¾-in drive ratchet and socket set (bridge connections and anchor terminals)

½-in drive ratchet and socket set with 3" and 10-in extensions

7/16-in to at least 1⅛inch sockets

One 20-in adjustable wrench

Five 1¼-in bell sockets

110-lb sledge hammer

4½-in drive sockets

118-lb sledge hammer

Four splice pins

115-in adjustable wrench

Four vise grip pliers

Combo open end and box wrench set 5/16 to 1¼ inch

Two 4lb. hammers

Post puller

Chain saw

Two flat shovels

Cut-off saw

Two round shovels

Saw blades

Two digging bars

Mix oil for saws

Two- post-hole diggers

Bar oil

Long, heavy-duty jumper cables

Two or three gallon mix gas cans

Two 5-gal gas cans

Acetylene Torch Set

Ink markers

3500-watt generator

Two 100-ft electric cord

Two ½-in VSR drills

Two 1-in step bits

Three ⅞-in hole saws

Two ½-in impact wrenches

Two ½-in impact wrenches

Two ½-in impact wrenches

Four swivel sockets

Two 5/16-in impact sockets

Two 1⅛-in impact socket

Three 1¼-in impact bell socket

Two 1¼-in impact deep bell sockets

HILTI concrete drill set with bits ½, ⅝, ⅞, 1 inch

Clipboard, time sheets, quantity sheets

Epoxy

Dust mask

Line levels

Construction Log Book

Line pins

G/R Standards and Specifications

String line

Cell phone

Credit cards

Paint & cold galv.

Accident Investigation Reports

Two pull binders

Camera

Proper work zone signs & stands

200-ft steel tape

STOP / SLOW paddles / cones

First-aid kit

Blood-born pathogen kit

First-Aid Reports

M.O.T. Standards

5 gal water cooler

Penetrating oil / spray

Wasp and bee spray

MSDS manual, hazard communication, safety manuals

Hard hats, safety vests, safety glasses, gloves, hearing protection

4. ESTIMATING TIME NEEDED FOR REPAIR

General guidelines:

  1. Include travel time to and from the repair site when this is a maintenance activity scheduled from a central garage.
  2. Plan about 30 to 45 minutes to place the traffic control devices. It will take about the same time to gather the control devices after repair work is completed.
  3. Allow 30 minutes for final inspection of guardrail after finishing the repair and for recording the repair job.
  4. The time needed to make ANY repair depends on the experience and skill of the crew. The number of workers for the job and the amount of power-assisted tools available will also affect the time required.

Repairing cosmetic damage to guardrail installations--Should your agency want to repair the very minor type of damage mentioned earlier in this handbook, the actual repair (which may only be painting or minor straightening of a dented rail) should not require more than 30 minutes to 1 hour.

Repairing damage that still permits the guardrail to function --When the inspection of the damage at the site indicates:

Or other conditions exist that permit routine scheduling of the repair (rather than emergency repair), plan for 1 to 2 hours of repair time, plus traffic control, inspection, and recording.

Repairing major damage requiring prompt attention--When the guardrail damage is extensive, such as four or more posts are knocked out or several rail beam sections are broken, plan on one half day time requirement, including the traffic control setup, inspection, and recording.

FOR AGENCIES WITH MAINTENANCE MANAGEMENT SYSTEMS THAT GIVE A MORE DETAILED TIME BREAKDOWN, USE THAT TO ESTIMATE TIME.

5. ESTIMATING CREW SIZE

The crew size will depend upon the extent of the damage and the needs for traffic control. Two workers and a person in charge should be enough to repair minor damage where the guardrail is allowed to remain assuming the guardrail would function satisfactorily while the repair was scheduled. This assumes the work involves only a few posts or rail beam sections. When four or more posts are involved, or more than two rail beam sections are to be replaced, expect to need a crew of four. If a wide range of power-assisted tools is available, then a crew of three should work well.

Traffic control crew needs are as follows:

  1. If no person is to be assigned to flag traffic through the repair work zone, then no additional workers are needed. Workers repairing the rail can place and collect the traffic control devices. There can be situations causing short-term encroachment on the road to move equipment or to make brief repairs. Provide warning to traffic in such cases.
  2. Assign one worker as a flagger when the traffic cones or temporary barricades around the repair site restrict the road or street to alternating one-way traffic. USE ONE FLAGGER WHEN THAT WORKER CAN CLEARLY SEE TRAFFIC APPROACHING THE REPAIR SITE FROM BOTH DIRECTIONS AND THE FLAGGER SIGNAL CAN BE SEEN BY DRIVERS WELL IN ADVANCE OF THE REQUIRED STOP POINT.
  3. ssign two workers as flaggers for any other work zone conditions where traffic cones or barricades create alternating one-way traffic flow around the repair.

IF YOUR MAINTENANCE MANAGEMENT SYSTEM GIVES MORE DETAILED CREW SIZE INFORMATION BY WORK TASK FOR GUARDRAIL REPAIR, THEN USE THAT CREW SIZE ESTIMATE.

6. EXAMPLE W-BEAM GUARDRAIL REPAIR LOG

W-beam guardrail repair log

Image. This is a scanned copy of a sample w-beam guardrail repair log.\ d

APPENDIX B: VIRGINIA DOT REPAIR GUIDANCE

The following Instructional and Informational Memorandum can be found at: http://www.extranet.vdot.state.va.us/locdes/electronic%20pubs/iim/IIM220.pdf

VIRGINIA DEPARTMENT OF TRANSPORTATION

LOCATION AND DESIGN DIVISION

INSTRUCTIONAL AND INFORMATIONAL MEMORANDUM

GENERAL SUBJECT:

GUARDRAIL REPAIR, REPLACEMENT AND UPGRADE GUIDELINES

NUMBER: IIM–LD–220.2

MM – 327 CD – 2003 – 4

SPECIFIC SUBJECT:

DATE:

NOVEMBER 21, 2003

SUPERSEDES: IIM–LD–220.1

TE – 305 CD – 2001 – 9

LOCATION AND DESIGN DIVISION APPROVAL:

Mohammad Mirshahi, P.E.

Approved November 12, 2003

SCHEDULING & CONTRACT DIVISION APPROVAL:

W. Byron Coburn, Jr., P.E.

Approved November 19, 2003

MOBILITY MANAGEMENT DIVISION APPROVAL:

Raymond J. Khoury, P.E.

Approved November 20, 2003

ASSET MANAGEMENT DIVISION APPROVAL:

James R. Smith, Jr.

Approved November 21, 2003


CURRENT REVISION



EFFECTIVE DATE


POLICY


  1. When located within the project limits of a construction project. When the line of rail extends outside the project limits, if more than 60% of the existing substandard line of rail lies within the project limits, then the entire run shall be replaced/upgraded as a part of that project.
  2. When guardrail needs to be repaired/replaced under a maintenance project and/or contract (e.g. guardrail, pavement, etc.).

    During routine maintenance projects and/or contracts of any roadway, all guardrail shall be reviewed, deficiencies identified, costs budgeted, and schedules set for replacement or upgrading to ensure that all existing guardrail meets current VDOT Standards. During these reviews if the guardrail is found to be more than 75 mm (three inches) lower or 75 mm (three inches) higher than current Standard requirements, then replacement or resetting shall be scheduled as soon as possible. For strong post guardrail (Standard GR-2) no metal blockouts are to be replaced in-kind or installed new, and no washers will be used other than those for the last 15.2 meters (50 feet) of a trailing end anchorage.

  3. When located within the project limits of transportation improvements associated with permitted land development projects.
  4. When any road is taken into the State roadway systems, all guardrail must comply with current Standards, and must include NCHRP 350 approved terminals and rail systems.

GUARDRAIL TERMINALS – DAMAGED AND SUBSTANDARD



FIXED OBJECT ATTACHMENTS (FOA'S)



W-BEAM GUARDRAIL



CABLE GUARDRAIL (STANDARD GR-3) DAMAGE


APPENDIX C: MAINTENANCE GUIDANCE

As resources (funding, staff, and equipment) allow, the following best practices are recommended as part of a regular maintenance program. Conduct an annual or biannual review of all W-beam guardrail in a jurisdiction. Keep a record of the inspection by date and person carrying out the inspection. This will be helpful in the event of a lawsuit resulting from a crash. Look for the following features:

Diagram. This diagram shows the placement of guardrail on a slope.

A useful tool for managing this asset is an inventory (with possibly a rating system) of existing W-beam barrier, indicating the type of W-beam (post and offset block material, rail material) and the type of end treatment (model name and materials). The inventory is also useful in setting priorities for improvement projects. The following is an example inventory system being developed by New York State DOT. For additional information on this inventory system, contact NYSDOT's Transportation Systems Maintenance, 50 Wolf Road, Albany, NY 12232; phone: 518-457-6435.

This image shows the New York State DOT guardrail inventory system repot. This is an electron form.
New York State Dot Guardrail Inventory System Report.

APPENDIX D: CLEAR ZONE DESCRIPTION

The concept of clear zone is an approach to minimize the number and severity of crashes involving vehicles running off the road. Simply stated, it is a traversable area that starts at the edge of the traffic lane and extends laterally a sufficient distance to allow a driver to stop or return to the road before encountering a hazard or overturning. The traversable area would be considered safe, if there were no fixed objects, unless they are breakaway, and if the roadside geometry (either the fore slope, back slope, or ditch) was flat enough that a vehicle could safely traverse the area without tipping and rolling over. Roadside safety features include breakaway sign and light posts, and traversable drainage structures. Curbs are not considered a roadside safety feature since they can be easily mounted by errant vehicles; hence, their presence does not alter how clear zone is measured.

Clear Zone Illustration

A safe traversable slope can be either a recoverable slope or a non-recoverable slope with a clear run-out area at the bottom. A recoverable slope is a slope on which a motorist may, to a greater or lesser extent, retain or regain control of a vehicle and recover or stop. Slopes 1:4 (Vertical:Horizontal) or flatter are generally considered recoverable. A non-recoverable, traversable slope is a slope which is considered traversable but on which an errant vehicle will continue to the bottom. Embankment slopes from 1:3 and 1:4 may be considered traversable but non-recoverable if they are smooth and free of fixed objects. A clear run-out area is the flatter area at the toe of a non-recoverable slope available for safe use by an errant vehicle. Slopes steeper than 1:3 are not considered traversable and should not be found in the clear zone.

The objective of roadside safety is to provide and maintain as much clear zone as practical. The design clear zone is the minimum width to be provided on a project and is dependent upon speeds, the roadside geometry, and traffic volumes. Further details on clear zone can be found in the Roadside Design Guide.


[1] Design can be seen at ftp://ftp.dot.state.tx.us/pub/txdot-info/cmd/cserve/standard/roadway/mbgtl205.pdf

[2] See Appendix D for description of clear zone.

Page last modified on March 15, 2012.
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