A Guide for Highway and Street Maintenance Personnel
November
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
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
Boone Boulevard, Suite 700
Vienna, VA -
PerformTech, Inc.
810 King Street
Alexandria, VA
11. Contract or Grant No. DTFH61-05-D-
12. Sponsoring Agency Name and Address
Office of Safety
Federal Highway Administration
U.S. Department of Transportation
New Jersey Avenue, S.E.
Washington, D.C.
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 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 .
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-. 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:
- Edward Denehy, New York State Department of Transportation
- Thomas Nutini, Franklin County (OH) Engineer's Office
- Dennis Randolph, P.E., Calhoun County (MI) Road Commission
- Gary Rohrer, P.E., Washington County (MD) Public Works Department
- Glenn Schulte, Utah Department of Transportation
TABLE OF CONTENTS
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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.
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:
- Standard section-the main section that shields the obstacle.
- Transition section-which applies when the guardrail ties into a bridge rail or other barrier system.
- Terminal(or End Treatment) section-the initialsection at the upstream (beginning) and downstream (end).
d
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.
Return to top
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:
- Guardrail is no longer reasonably functional.
- Guardrail should function adequately under a majority of impacts.
- 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
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.
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.
Rail is bent/pushed out of line less than 12 inches &#; rail element is intact (no tears and full splices).*
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.
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.
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
- Tension capability is intact:
- No tears.
- Eight &#;-in splice bolts in each rail connection.
- No rail subjected to a cutting torch is reused; any new holes are drilled.
- Height is according to standard.
- 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.
- No washers under rail-to-post bolt head.
- 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).
- Lap rail elements in the direction of traffic (upstream {approach} rail is in front of downstream {leave} rail).
- 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.
- 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.
W-beam element is not attached to rigid object.
W-beam is severely pocketed in advance of the rigid object.
2. Damage:
Transition should function adequately under a majority of impacts.
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.
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 s
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:
Traditional transition.
Traditional transition.
- Foremost is a strong tension connection between the W-beam and the rigid object.
- More and/or larger posts close to the rigid object.
- A nested rail element for the last 12½ ft.
- Some means to prevent wheel snagging, such as a rub rail or curbing.
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
- Tension capability is intact:
- a. No tears in rail elements.
- Minimum of four &#;-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.
- All splices are intact (eight splice bolts in each rail connection)
- No rail
subjected to a cutting torch.
- Extra/larger posts &#; the last post spacing in advance of the rigid object should be 1 ft, 6¾ in.
- Nested last rail element.
- Rub rail or curb to prevent wheel snagging.
- Bridge shoe lapped in the direction of the near-side traffic.
- 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.
Non-energy-absorbing end treatment.
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 s, 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.
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
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.
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.
Turndown is obvious.
Breakaway Cable Terminal (BCT) No strut between posts 1 and 2. Standard posts beyond post 2. Bolts attach rail to each post.
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.
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.
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).
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.
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.
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- or requests to .
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).
Repaired/Replaced End Treatment Checklist:
- Use no interchanged parts from different manufacture's systems for parts
unique to the particular end treatment being repaired.
- For energy-absorbing systems, place the head completely onto the rail
element.
- For energy-absorbing systems, the cable anchorage to the rail element allows
the cable to release from the rail if the head slides.
- Post 1's top part will separate from its foundation for end-on impacts.
- 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.
- Grading provides no more than 4 inches above ground to the strut or to what will
remain as a stub.
- Bearing plate is properly oriented.
- Cable is tightened to a taut condition; cannot lift up on the
cable more than 1 inch.
- 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:
- Upon notification of damage and when the damage leaves the
guardrail nonfunctional, and it cannot be repaired immediately, warn traffic of
the hazard by putting out temporary warning devices in accordance with the
MUTCD, such as drums, vertical panels, cones, or other devices.
- Contact your local Dig Safe utility protection well in advance of
going to the site.
- Take enough signs and channelizing devices to the site to properly mark the repair zone. When
your agency uses an arrow board and / or a shadow truck or Truck Mounted
Attenuator (TMA), be certain there is enough equipment and personnel to
handle these items.
- et up the Temporary Traffic Control plan for the work area to
repair the guardrail, and ensure the Traffic Control Plan complies with the Manual
on Uniform Traffic Control Devices (MUTCD) or your agency requirements.
- Ensure all workers wear equipment as provided by the Occupational and Safety Administration (OSHA) or local
requirements, such as safety visibility vests, safety glasses, and protective-type shoes.
- Ensure all equipment and procedures conform to accepted OSHA guidance.
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:
- Disassemble damaged guardrail.
- Spray the connecting bolts with penetrating oil for easier removal. Unbolt the damaged rail-beam sections.
- 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.
- Pull out damaged posts.
- 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.
- 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.
- 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.
- 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.
- Drill or dig holes for the posts, if necessary.
- Set or drive posts to the proper height.
- Backfill and compact the soil around the posts.
- Check post alignment and height. Correct any major deviations.
- 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).
- If necessary,
use a drift pin to line up the holes for bolting.
- Make sure all 8 bolts are in place in each splice connection.
- Leave all
connections finger tight to allow for lengthwise adjustment after all sections
are installed.
- Final assembly
&#; when all rail is hung, go back and snugly tighten all bolts. There is no need
to overtighten.
- Cleanup &#;
smooth out the shoulder and slope approaching the guardrail so the next vehicle
to run into it has a smooth path.
- 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) &#;-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:
- 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.
- 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:
- Weakened wood posts, called CRT posts, that are 6 ft long and have 3½-in-diameter holes
drilled at ground line and 16 inches below the ground.
- Short wood posts 45 inches long with a 2½-in hole, which slip into steel foundation
tubes driven in the ground &#;foundation tubes have different lengths and may or
may not have soil plates attached to them.
- Steel posts that come in two parts and are attached by bolts at the ground line.
- Steel posts having two parts that are plug welded together.
- Steel posts that look like standard 6-ft steel posts, but have four holes in the
flanges at ground line; and more.
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:
- Completed Work Inspection Checklist (provided in Appendix A) is a simple record that
the repair was inspected when performed.
- Keep a copy of the Checklist of Materials for Repair worksheet (see appendix A,
Item 2) filled in with the parts you actually used. Write in salvaged or reused
parts by hand. Sign and date the materials checklist when the repair is
complete.
- If a camera is available, then take pictures of the condition before and after the
completed repair. Note the location and date of the repair on any printed
pictures.
REFERENCES
- Manual on Uniform Traffic Control Devices (MUTCD):
http://mutcd.fhwa.dot.gov/
- Standardized Highway Barrier Hardware Guide:
http://www.aashtotf13.org/Barrier-Hardware.php
- FHWA-accepted roadside hardware:
http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/
- End-treatment manufacturers:
Road Systems Inc: http://www.roadsystems.com/
Trinity Industries: http://www.highwayguardrail.com/
- AASHTO Roadside Design Guide:
https://bookstore.transportation.org/collection_detail.aspx?ID=105
- Guidelines for the Selection of W-beam Barrier Terminals: FHWA Publication FHWA-SA-06-19,
December (available from FHWA Report Center; request by at
)
APPENDIX A: ESTIMATING RESOURCES FOR W-BEAM GUARDRAIL REPAIR
1. EXAMPLE OF DAMAGE INSPECTION REPORT
Damage inspection Report &#; New York State DOT
Calculating Guardrail Radius (to complete form above)
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:
- 12-ft, 6-in steel W-beam rail sections
(matching existing material &#; gauge, galvanizing, treated, or "rusting
steel", etc.).
- Eight each 5/8-in by 1¼-in
galvanized buttonhead bolts with recessed nuts for each rail splice.
- One each, &#;-in rail-to-post
galvanized buttonhead bolt with round washer and recessed nut for
fastening rail to post; length varies depending on the type of offset
block and type of post:
- Wood block to wood post: 18 inches.
- Wood or approved block to steel post: 10 inches.
- Steel block to steel post: 2 inches (no washer on back + 2 each &#;1½-in bolts to connect blockout to post).
- One each, 1-ft, 2-in wood offset
block for wood post or approved offset block for steel post, to space the
rail away from the post to minimize snagging.
- 6-ft, 0-in posts. To agency
standard (6 by 8 or 8 by 8 wood posts or W6 by 8.5 or W6 by 9 steel posts.
- 12-in galvanized W-beam backup
plate at intermediate steel post locations with steel offset block for
placing behind rail where no rail splice occurs.
- 10d to 16d galvanized nail(s) to
keep wood offset block from rotating on wood post.
Traffic
W-Beam with Wood Offset Block on Wood Post
Traffic
W-Beam with Approved Offset Block on Steel Post
Traffic
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
&#;-in
by 1¼ -in-long splice bolts with nuts
(#
sections x 8) + 8
&#;&#;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:
&#;
-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
&#;-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 1&#;"
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 1&#;-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
If you are looking for more details, kindly visit Galvanized Highway W Beam Guardrail.
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, &#;,
&#;, 1-in bits
3 7/8&#;inch-hole saws
Epoxy
Long heavy-duty jumper
cables
Ink markers
Acetylene torch set
Two chisels
-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
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
&#;-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
1&#;inch 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
-watt generator
Two 100-ft electric
cord
Two ½-in VSR drills
Two 1-in step bits
Three &#;-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 1&#;-in impact
socket
Three 1¼-in impact
bell socket
Two 1¼-in impact deep
bell sockets
HILTI concrete drill
set with bits ½, &#;, &#;, 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
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:
- Include travel time to and from the repair site when this is a maintenance activity scheduled
from a central garage.
- 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.
- Allow 30 minutes for final inspection of guardrail after finishing the repair and for recording
the repair job.
- 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:
- Only a few posts are broken.
- Only a few posts are pushed badly off line.
- A rail is bent out of line less than 18 inches.
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:
- 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.
- 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.
- 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
\ 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
&#; &#; 4
SPECIFIC SUBJECT:
DATE:
NOVEMBER 21,
SUPERSEDES:
IIM&#;LD&#;220.1
TE
&#; 305 CD &#; &#; 9
LOCATION AND DESIGN DIVISION APPROVAL:
Mohammad Mirshahi,
P.E.
Approved November
12,
SCHEDULING
& CONTRACT DIVISION APPROVAL:
W. Byron Coburn,
Jr., P.E.
Approved November
19,
MOBILITY MANAGEMENT DIVISION APPROVAL:
Raymond
J. Khoury, P.E.
Approved
November 20,
ASSET MANAGEMENT DIVISION APPROVAL:
James
R. Smith, Jr.
Approved
November 21,
CURRENT REVISION
- This memorandum has been revised for clarification and emphasis in several
areas.
EFFECTIVE DATE
- These instructions are effective upon receipt.
POLICY
- These instructions apply to the Repair, Replacement and Upgrade of Existing Guardrail
Installations Only. New Installations SHALL be in accordance with current VDOT Standards.
- For the following situations all existing substandard guardrail systems and
components shall be upgraded to the latest standard in accordance with
current VDOT Road and Bridge Standards and this memorandum.
- 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.
- 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.
- When
located within the project limits of transportation improvements associated
with permitted land development projects.
- 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
- All terminals shall be installed as they were tested in accordance with
NCHRP 350. Lapping of guardrail must be in the direction of traffic, per
NCHRP 350 testing. DO NOT CHANGE THE DIRECTION OF THE LAPPING.
- When terminal damage occurs, a site investigation shall be made to determine whether
the terminal should be repaired, replaced or eliminated. If a gap exists
between two runs of guardrail and it is approximately 60 meters (200 feet)+ , closing the gap by continuing the run of guardrail is recommended, thereby
eliminating the need for a terminal. If a cut slope is within approximately 60
meters (200 feet) + longitudinal distance from the location of the
terminal and is sufficient to install a Standard GR-6, the guardrail shall be
extended to the cut slope and a cut slope terminal (Standard GR-6) should be
used.
- If
the installation site does not provide at least 22.8 meters (75 feet ) of clear
run-out path in addition to the length of need required for the barrier
(exclusive of the terminal), a parallel terminal (Standard GR-9) shall be used
instead of a flared terminal (Standard GR-7). If an extensive amount of
grading would be required for site preparation to install a flared terminal
(Standard GR-7), consideration should be given to using a parallel terminal
(Standard GR-9) that does not require as much site preparation.
- The site preparation for all installations shall be in accordance with current
Standards.
- Before replacing a damaged or substandard terminal, the location of the existing terminal
should be checked to ensure sufficient length of need has been provided in the
run of guardrail to adequately shield the hazard for which it was installed.
In some cases it may be necessary to extend the guardrail to better shield the
hazard or to provide for a more suitable site that would not require grading.
- Breakaway Cable Terminals (BCT's)
BCT's had concrete footings for the
first two posts, did not have the metal strut at ground level between the first
two posts and all posts were not breakaway.
Completely replace BCT's with new NCHRP 350 approved terminals whenever they are damaged or if
they are within the limits of a construction or maintenance project/contract.
- Modified
Eccentric Loading Terminals (MELT's)
The MELT provides a 1.2-meter (4-foot) offset, a 1.5-meter (5-foot) flat area behind the first post
and a metal strut at ground level between the first two wooden breakaway posts.
If the MELT (Standard GR-7) is improperly installed or when damage includes the nose assembly and
first two posts, replace with new NCHRP 350 approved terminals (revised
Standard GR-7) such as the SRT-350, FLEAT 350, REGENT or other approved NCHRP
350 product. When replacing substandard GR-7 terminals, make sure that the
section of rail and posts adjoining the new terminal installation is at the
proper height.
- Strong Post Turned-down Terminals (Std. GR-5's)
All turned-down strong post terminals
(run-on locations) should have already been removed from roadways on the
National Highway System. Any that have not been removed shall be removed
immediately.
When these terminals that may remain
on non-NHS roadways are damaged, they shall be replaced with NCHRP 350 approved
terminals.
- Weak Post Turned-down Terminals (Std. GR-8, Type II's)
Since no weak post terminals have been
approved in accordance with NCHRP 350 for use in run-on locations, any of these
terminals that are damaged shall be replaced with NCHRP 350 approved strong
post terminals incorporating the appropriate transition required between a
strong post terminal and weak post guardrail (in accordance with VDOT Road and
Bridge Standards), regardless of the design speed of the roadway.
Any weak post run-on terminals within
the limits of a construction project, maintenance project and/or contract shall
be upgraded as part of the project.
For run-off locations, turned down
terminals incorporating a concrete anchor (Standard GR-8, type I or II) are
acceptable, regardless of the design speed of the roadway; however, the Type I
and II terminals shall be outside of the clear zone of opposing traffic on
two-way roadways. This includes existing installations in locations with
design speeds greater than 70 km/h (45 mph) for which new installation of weak post guardrail must be in accordance with the new approved TL-3 weak
post design.
- TERMINALS
BURIED IN THE CUT SLOPE (OLD STANDARD GR-6)
Existing GR-6 installations that are not NCHRP 350 compliant (in accordance with current VDOT Standards) should be evaluated to ensure the following:
- Proper
Height per current standards -
Where existing GR-6
Terminals were installed with the height of rail following the ground line at a
height of 27" to 28", this installation method caused the terminals to be low,
both in front of and behind the ditch line. These low installations may allow
an errant vehicle to vault over the top rail and go behind the guardrail,
failing its intended protection from hazards.
- The
end anchorage is sufficiently buried in the slope 0.3 m (min. 1 foot cover).
Repair or replacement
of either of these situations shall be to current VDOT Standards.
FIXED OBJECT ATTACHMENTS (FOA'S)
- Whenever
a substandard fixed object or BR-GR attachment is damaged, it shall be replaced
or upgraded with current Road and Bridge Standard fixed object attachments including
the nesting of the rail, shortened post spacings and rubrail.
- When
substandard FOA's or BR-GR's exist within the limits of construction projects
or when replacement is required under a guardrail maintenance project and/or
contract; both FOA's and BR-GR's shall be upgraded or replaced in accordance
with the current VDOT Road and Bridge Standard.
W-BEAM GUARDRAIL
- During NEW CONSTRUCTION, always
install to the current Standard heights.
- ALL
W-beam guardrail panels shall be lapped in the direction of traffic. With
two-way traffic, the laps on the right side of traffic are to be in the
direction of traffic or toward the downstream end.
- Any existing guardrail (GR-2, GR-8) that does not meet current VDOT Standards or is identified to be greater than 75 mm (three inches) higher or
lower than the Standard for the system being used, shall be scheduled for
resetting or replacement. For sections of guardrail that are longer than 60
meters (200 feet), if more than 60% of the entire run has been damaged, or does
not meet current Standards, the entire run shall be replaced with current
Standards. If less than 60% of the entire run has been damaged, the damaged
section should be replaced with current Standards.
- Weak post W-beam Guardrail (Std. GR-8)
When substandard GR-8 is damaged, the extent of damage should govern repair/replacement. If the
total run of guardrail is 60 meters (200 feet) or less, the entire run shall be
replaced with the latest GR-8 design (which meets NCHRP 350 Test Level 3
criteria) or if the particular site conditions are appropriate a Standard GR-2
or GR-3 system can be used.
For substandard sections of GR-8 guardrail that are longer than 60 meters (200 feet), if more
than 60% of the entire run has been damaged, or does not meet current
Standards, the entire run shall be replaced with the latest GR-8 design or if
the particular site conditions are appropriate a Standard GR-2 or GR-3 system
can be used.
If less than 60% of the entire run has been damaged, the damaged section should be replaced with
the latest GR-8 design or if the particular site conditions are appropriate a Standard GR-2 system can be used.
When either of these designs is used, the proper transitions MUST be incorporated. Transitions to
the new height, splice locations and backup plates for the GR-8, and for the
GR-2 transitions from GR-8, 8A, 8B to the GR-2 must be done in accordance with
current Standard designs. The latest GR-8 design can be used even for speeds
greater than 70 km/h (45 mph).
Existing weak post W-beam, not meeting NCHRP 350, that is within the limits of a reconstruction or
maintenance project shall be upgraded to the new Standard design. When
resetting or reusing rail, the height of the rail shall be installed to meet
the current VDOT Road and Bridge Standards.
- Strong Post W-beam with 12' 6" Post Spacing and no blockout (Std. GR-1)
All Standard GR-1
guardrail should be identified and replacement schedules set for all roadway
systems so that appropriate funding can be budgeted for upgrades. Standard
GR-1 on any roadway within the National Highway System (NHS) shall receive
first priority for upgrading as soon as possible.
Existing strong post
guardrail (Standard GR-1) and end terminals within the project limits of any
project/contract should always be replaced with a new NCHRP 350 approved
system.
When damaged, the extent of damage should govern repair/replacement. If the total run of
guardrail is 60 meters (200 feet)+ or less, the entire run shall be
replaced with strong post (Standard GR-2) guardrail.
For sections of guardrail that are longer than 60 meters (200 feet), if more than 60% of the
entire run has been damaged, the entire run shall be replaced with strong post
(Standard GR-2) guardrail. If less than 60% of the entire run has been
damaged, the damaged section should be replaced with strong post (Standard
GR-2) guardrail.
- Strong Post W-beam Guardrail with Steel Posts (Std. GR-2)
When damaged, replace in kind in accordance with current standards; NO STEEL BLOCKOUTS
shall be used. Rectangular washers shall be removed on a regular run
of guardrail with the exception that washers should still be retained or added
to the last 15 meters (50 feet) of a trailing end to provide end anchorage on
the run-off end of a one-way roadway. Discard the steel blockouts and use
routed 150x150x360 mm (6"x6") wood or composite blockouts. The wood and
composite blockouts can be used interchangeably within a single run of
guardrail for both NEW or repair,replacement and upgrades. When existing
150x200x360 mm (6x8) wood or composite blockouts are replaced during repairs,
the blockouts shall include routing to prevent blockouts from rotating. When
wood posts with wood blockouts are used, they should have TWO nails (one
on each side) to prevent rotation of blockouts.
When posts are removed and meet current specifications for reuse, they should be reused only if they are 1.75 m (5' 9") or longer with Standard wood or composite
blockouts. When resetting rail, the posts shall be removed and the holes
backfilled prior to reinstalling the posts. The height of the rail should be
measured to ensure it meets the current VDOT Road and Bridge
Standards.
CABLE GUARDRAIL (STANDARD GR-3) DAMAGE
- When
damaged, replace in kind in accordance with current VDOT Road and
Bridge Standards (Standard GR-3).
- Any existing GR-3 that is identified to be more than 75 mm (three inches) lower or
75 mm (three inches) higher than current Standard requirements shall be
scheduled for resetting.
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:
- Continuity of tension is preserved: no tears in the W-beam elements, all eight bolts
are in each splice; all transitions are firmly connected to rigid objects;
anchor cables are firmly attached to rail and posts.
- Rail height is adequate. Erosion
and debris buildup can affect the effective rail height. Identify rail
significantly low &#; 24 inches or less &#;or rail significantly high &#; more
than 30 inches &#;for upgrading or modification, as resources permit.
- Integrity of the material is
sound: no significant corrosion of the steel in the rail elements
(especially watch for rusting steel), the offset blocks, or the
posts, and no significant rotting of wood material.
- The amount of guardrail in
advance of the hazard (length of need) is long enough to adequately shield
the hazard.
- Identify older, nonstandard
W-beam (or other types) systems (such as nonblocked out rail).
- For end treatments, ensure post
#1 is sound and connected to its foundation.
- For energy-absorbing end
treatments, the impact head is attached to post 1.
- The grading around the end
treatment allows a small vehicle impacting on the end to pass over any
remaining foundation/post/strut.
- Ensure adequate, available
deflection distance (generally 3 ft for the standard W-beam system) to
vertical rigid objects.
- Flare (the rate at which the
guardrail moves closer to the travel way going downstream) is not
excessive (not sharper than 7:1).
- Check for adequate soil backing
(1ft of 3:1 or flatter soil for standard 6-ft posts) to provide the
stiffness for the posts.
- Ensure guardrail located on a
steeper slope is in compliance with the figure below in order to prevent
vaulting.
- Ensure the offset blocks are not
rotated.
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 ; : 518-457-.
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.
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.
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