Structures Design Guidelines | July 2007
6 - Superstructure Components |

## 6.7 Traffic Railing [13.7] (07/06) July 2006 Updated References from "Structures Standards" to "Design Standards."

### 6.7.1 General (01/07) Jan 2007 - Revised B. and added C.

A. Unless otherwise approved, all new bridge, approach slab and retaining wall mounted traffic railings, traffic railing/sound barrier combinations and traffic railing/glare screen combinations proposed for use in new or temporary construction, resurfacing, restoration, rehabilitation (RRR) and widening projects must:

1.) Have been successfully crash tested to Test Level 4 (minimum), Test Level 5 or Test Level 6 criteria (as appropriate) in accordance with National Cooperative Highway Research Program (NCHRP) Report 350 and LRFD for permanent installations.

2.) Have been successfully crash tested to Test Level 3 (minimum) in accordance with NCHRP Report 350 and LRFD for temporary installations shielding drop-offs.

3.) Have been successfully crash tested to Test Level 2 (minimum) in accordance with NCHRP Report 350 and LRFD for temporary installations shielding work zones without drop-offs (45 mph or less design speed).

4.) Meet the appropriate strength and geometric requirements of LRFD Section 13 for the given test levels and crash test criteria.

5.) Be upgraded on both sides of a structure when widening work is proposed for only one side and the existing traffic railing on the non-widened side does not meet the criteria for new traffic railings.

6.) Be constructed on decks reinforced in accordance with Chapter 4 for permanent installations on new construction, widenings and partial deck replacements.

7.) Be constructed on decks and walls meeting the requirements of Section 6.7.4 for retrofit construction.

8.) Be constructed and installed in accordance with the crash tested and accepted details for temporary installations.

B. The traffic railings shown on Design Standards Index Nos. 411-414, 420-425 and 470-483 have been determined to meet the applicable crash testing requirements and should be used on structures in Florida. The applicability of each of these standard traffic railings in permanent installations is addressed in the Plans Preparation Manual, Volume I.

C. Evaluate existing installation of superseded FDOT Standard Traffic Railings and supporting bridge decks, wing walls and retaining walls as follows:

1.) All superseded FDOT Standard Traffic Railings shown in the Structures Manual Volume 3, Instructions for Design Standards Existing FDOT Traffic Railing Details are both structurally and functionally adequate. Refer to these drawings for information on existing "New Jersey Shape" and "F Shape" Traffic Railings.

2.) Existing bridge decks, wing walls and retaining walls supporting traffic railings referenced in C.1 are considered to be both structurally and functionally adequate for resisting vehicular impact loads.

3.) Traffic railings and existing bridge decks, wing walls and retaining walls referenced in C.1 and C.2 do not require a variance or an exception for vehicular impact loads.

### 6.7.2 Non-Standard or New Railing Designs (01/06) Jan 2006 Per TDB C05-14, replaced paragraph B. Added Paragraph E. and commentary after Paragraph D.

A. The use of a non-FDOT standard or new structure mounted traffic railing requires the prior approval of the Structures Design Office. Proposed modifications to standard traffic railings also require prior Structures Design Office approval. Such proposed modifications may include but are not limited to reinforcement details, surface treatments, material substitutions, geometric discontinuities, non-standardized attachments, end transition details and traffic face geometry.

B. Submit all proposed non-FDOT standard, new or modified structure mounted traffic railing designs to the Structures Design Office for review and possible approval. Make this submittal early in the design process preferably prior to submittal of the Typical Section Package.

C. A non-FDOT standard or new structure mounted traffic railing design may be approved by the Structures Design Office if it meets the requirements of No. 1 and Nos. 2, 3 or 4 below:

1.) The Structures Design Office has determined that the design will provide durability, constructability, and maintainability equivalent to the standard FDOT traffic railing designs.

2.) It has been successfully crash tested in accordance with NCHRP Report 350 Test Level 4 (minimum) criteria for permanent installations and Test Level 2 or 3 criteria (as appropriate) for temporary installations.

3.) It has been approved for specific uses by FHWA after evaluation of results from successful crash testing based on criteria that predate NCHRP Report 350 Test Levels 2, 3 and 4 (as appropriate).

4.) It has been evaluated by the Structures Design Office and identified as similar in strength and geometry to another traffic railing that has been successfully crash tested in accordance with NCHRP Report 350 Test Level 4 (minimum) criteria for permanent installations and Test Level 2 or 3 criteria (as appropriate) for temporary installations.

Commentary:

The background for this policy is based on the Test Level Selection Criteria as defined in Section 13 of the AASHTO LRFD Bridge Design Specifications and on historical construction costs and in-service performance of standard FDOT Test Level 4 traffic railings used in permanent installations. This background can be summarized as follows:

1. In general, a greater potential exists for overtopping or penetrating a shorter height, lower test level traffic railing versus a similarly shaped Test Level 4 traffic railing. This potential is further aggravated on tall bridges and on bridges over intersecting roadways or water deep enough to submerge an errant vehicle. Vehicle performance during higher speed impacts is also more critical on lower test level traffic railings.

2. Little construction cost savings can be realized by using a lower test level traffic railing. In some cases, particularly with the more elaborate or ornate traffic railing designs, initial construction costs and long term repair and maintenance costs could actually be greater than those for a standard FDOT Test Level 4 design.

3. Aesthetically pleasing and open Test Level 4 designs are available for use where appropriate.

4. On bridges and retaining walls with sidewalks where special aesthetic treatments are desired or required, the use of an aesthetic pedestrian railing located behind a Test Level 4 traffic railing is a more appropriate solution. The aesthetics of the traffic railing should complement the pedestrian railing.

D. For more detailed information on FDOT structure mounted traffic railings, refer to the Design Standards. For additional information about crash-tested traffic railings currently available or about traffic railings currently under design or evaluation, contact the Structures Design Office.

E. Use the traffic railing surface texture guidelines given below for the selection of proposed texturing of the traffic face of 32-inch and 42-inch Vertical Face Traffic Railings and the upper vertical portion of the Traffic Railing/Sound Barrier combination. Maintain SDG 1.4 concrete cover requirements
at the point of deepest relief. Modify standard concrete products to maintain the proper cover but do not modify the geometry of the traffic face of the railing.

1.) Sandblasted textures covering the majority of the railing surface with a maximum relief of 3/8-inches.

2.) Images or geometric patterns inset into the face of the railing 1-inch or less and having 45-degree or flatter chamfered or beveled edges to minimize vehicular sheet metal or wheel snagging.

3.) Textures or patterns of any shape and length inset into the face of the railing up to 1/2-inch deep and 1-inch wide and having 60-degree or flatter chamfered or beveled edges to facilitate form removal.

4.) Any texture or pattern with gradual undulations (e.g. cobblestone) that has a maximum relief of 3/4-inch over a distance of one foot.

F. Patterns or textures must be cast into or otherwise integral with the traffic face or top of traffic railings. Do not specify textures, patterns or features, e.g. brick, stone, or tile veneers, etc. on the traffic face or top of traffic railings that have to be attached a separate element. Such features may be considered for attachment to the back face of traffic railings and pedestrian railings on a project by project basis in locations not over or directly beside other travelways.

Commentary:

The above guidelines for concrete railing texturing will not adversely affect the NCHRP Report 350 test level of the railing to which a texture or pattern is applied. However, it is clear from crash test results that textured railings can result in more vehicular body damage in a crash due to increased friction even if crash performance remains within acceptable limits.

Aesthetic attachments to the back of the traffic railing may become dislodged when the railing is impacted and create a hazard to roadways located under or beside the structure. For this reason, aesthetic attachments shall not be used on the back of railings located over or directly beside other travelways. Railings with aesthetic features generally cannot be slip formed resulting in increased construction time and cost.

The selection of a proposed railing texture or pattern should take into account the overall aesthetic concept of the structure, maintainability of the feature and the long service of the structure. Shapes of traffic railings create the major aesthetic impression, colors, textures, and patterns are secondary. Form liners that try to imitate small scale detail are wasted at highway speeds but may be appropriate for areas with pedestrian traffic.

### 6.7.3 FHWA Policy

A. Since September 1, 1986, the Federal Highway Administration (FHWA) has required highway bridges on the National Highway System (NHS) and the Interstate Highway System to have crash-tested railing. Current policy is stated in the following documents:

1.) Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA).

http://www.fhwa.gov/legsregs/legislat.html

Required that measures to enhance the crashworthiness of roadside features accommodate vans, minivans, pickup trucks, and 4-wheel drive vehicles, as well as cars.

2.) National Cooperative Highway Research Program (NCHRP) Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features.

http://safety.fhwa.dot.gov/programs/roadside_hardware.htm

Provides guidance for testing highway features to assess safety performance of those features. Guidance includes definitions of crash-test levels with specified vehicle, speed, and impact angle for each level.

3.) May 30, 1997, memorandum from Dwight Horne on the subject of "Crash Testing of Bridge Railings."

http://safety.fhwa.dot.gov/fourthlevel/hardware/pdf/bridge.pdf

Identifies 68 crash-tested bridge rails, consolidating earlier listings and establishing tentative equivalency ratings that relate previous testing to NCHRP Report 350 test levels.

4.) July 25, 1997 memorandum from Donald Steinke on the subject of "Identifying Acceptable Highway Safety Features." http://fhwa.dot.gov/legsregs/directives/policy/ra.htm

Clarifies and summarizes policies on bridge traffic railing, points to authorities for requiring testing of bridge traffic railing, and identifies methods for submitting new rails for testing. This document also identifies exceptions, one of which is the replacement or retrofitting of existing bridge traffic railing unless improvements are being made on a stretch of highway that includes a bridge with obsolete railing.

B. On its web site, FHWA provides current information on three general categories of roadside hardware that are tested and evaluated using NCHRP Report 350 criteria; one of those categories is Bridge Railing.

See Bridge Railings at http://safety.fhwa.dot.gov/fourthlevel/hardware/bridgerailings.htm

### 6.7.4 Existing Obsolete Traffic Railings (01/06)

A. General

1.) FDOT promotes highway planning that replaces or upgrades non-crash tested traffic railing on existing bridges to current standards, or that at least increases the strength or expected crash performance of these traffic railings. FDOT has developed two sets of Design Standards, Index 470 and 480 Series, for retrofitting existing structures with traffic railing types that have performed well in crash tests and are reasonably economic to install. Detailed instructions and procedures for retrofitting obsolete traffic railings on existing structures are included in Volume 3 "Instructions for Designers".

2.) For RRR projects, existing bridge traffic railing retrofits constructed in accordance with 1987 through 2000 Roadway and Traffic Design Standards, Index 401, Schemes 1 and 19 Concrete Safety Barrier and Scheme 16 Guardrail Continuous Across Bridge and their accompanying approach and trailing end guardrail treatments may be left in place provided they meet the criteria set forth in the Plans Preparation Manual, Volume I, Sections 25.4.25.3 and 25.4.26.2.

3.) When rehabilitation or renovation work is proposed on an existing structure with traffic railings that do not meet the criteria for new or existing railings as provided above, replace or retrofit the existing traffic railings to meet the crash-worthy criteria unless an exception is approved. Refer to Chapter 23 of the Plans Preparation Manual, Volume 1, for information about exceptions.

Commentary: The obsolete standard entitled Guardrail Anchorage and Continuous Barrier for Existing Bridges, Index No. 401, was included in the Roadway and Traffic Design Standards from 1987 until 2000. Schemes 1 and 19 of this standard entitled Concrete Safety Barrier are based on a design that has been crash tested as documented in Transportation Research Report TRP-03-19-90 and accepted by FHWA at NCHRP Report 350 Test Level 4. Scheme 16 of this standard entitled Guardrail Continuous Across Bridge has been structurally evaluated and has been determined to be acceptable to FDOT and FHWA to leave in place on RRR projects provided the installation meets the criteria given herein.

Specify in the Plans the necessary upgrades to the existing guardrail transitions as follows.

For the w-beam approach transition shown as Detail J in the 1987 edition of the Roadway and Traffic Design Standards, Index 400 without a continuation of curb beyond the bridge or approach slab, use the following Plan Sheet note placed adjacent to bridge ends:

Construct Transition Block, nested W Beam Guardrail and additional Guardrail Posts and Offset Blocks as shown in Interim Design Standards Index 403.

For the nested w-beam approach transition shown as Detail J in the 1987 edition of the Roadway and Traffic Design Standards, Index 400 with a continuation of curb beyond the bridge or approach slab, use the following Plan Sheet note placed adjacent to bridge ends:

Construct nested W Beam Guardrail and additional Guardrail Posts and Offset Blocks as shown in Interim Design Standards Index 403.

For the nested w-beam approach transition shown as Detail J in the 1998 edition of the Roadway and Traffic Design Standards, Index 400 without a continuation of curb beyond the bridge or approach slab, use the following Plan Sheet note placed adjacent to bridge ends:

Construct Transition Block as shown in Interim Design Standards Index 403.

For all trailing end treatments, specify the necessary guardrail upgrades as appropriate.

B. FHWA Policy on Existing Traffic Railings

The FHWA requires that bridge railing on the National Highway System (NHS) meet requirements of NCHRP Report 350:

"all new or replacement safety features on the NHS covered by the guidelines in the NCHRP Report 350 that are included in projects advertised for bids or are included in work done by force-account or by State forces on or after October 1, 1998, are to have been tested and evaluated and found acceptable in accordance with the guidelines in the NCHRP Report 350 " (See Section 6.7.3, Number 4).

However, FHWA softens this requirement somewhat by allowing exceptions:

"Bridge railings tested and found acceptable under other guidelines may be acceptable for use on the NHS." This is a specific reference to the Horne memo titled "Crash Testing of Bridge Railings" (See Section 6.7.3, Number 3.)

"The FHWA does not intend that this requirement (that new safety features installed on the NHS be proven crashworthy in accordance with the guidelines in the NCHRP Report 350) result in the replacement or upgrading of any existing installed features beyond what would normally occur with planned highway improvements."

This statement is qualified by a requirement that states have a "rational, documented policy for determining when an existing non-standard feature should be upgraded."

C. Traffic Railing Retrofit Concepts and Standards

Existing non-crash tested traffic railings designed in accordance with past editions of the AASHO and AASHTO Standard Specifications for Highway Bridges will likely not meet current crash test requirements and will also likely not meet the strength and height requirements of the AASHTO LRFD Bridge Design Specifications. The retrofitting of these existing non-crash tested traffic railings reduces the separate but related potentials for vehicle snagging, vaulting and/or penetration that can be associated with many obsolete, non-crash tested designs.

The Thrie Beam Guardrail Retrofit and Vertical Face Retrofit Design Standards, Index 470 and 480 Series, respectively, are suitable for retrofitting specific types of obsolete structure mounted traffic railings. These retrofits provide a more economical solution for upgrading obsolete traffic railings when compared with replacing the obsolete traffic railings and portions of the existing bridge decks or walls that support them. As these retrofits do not provide for any increase in clear width of roadway, and in a few cases decrease clear width by approximately 2 inches, they should only be considered for use on structures where adequate lane and shoulder widths, sight distances and transition lengths are present. The potential effects of installing a retrofit should be evaluated to ensure that the accident rate will not increase as a result. Detailed guidance and instructions on the design, plans preparation requirements and use of these retrofits is included in Volume 3 of the Structures Manual.

When selecting a retrofit or replacement traffic railing for a structure that will be widened or rehabilitated, or for a structure that is located within the limits of a RRR project, evaluate the following aspects of the project:

1.) Elements of the structure.

a.) Width, alignment and grade of roadway along structure.

b.) Type, aesthetics, and strength of existing railing.

c.) Structure length.

d.) Potential for posting speed limits in the vicinity of the structure.

e.) Potential for establishing no-passing zones in the vicinity of the structure.

f.) Approach and trailing end treatments (guardrail, crash cushion or rigid shoulder barrier).

g.) Strength of supporting bridge deck or wall.

h.) Load rating of existing bridge.

2.) Characteristics of the structure location

a.) Position of adjacent streets and their average daily traffic.

b.) Structure height above lower terrain or waterway.

c.) Approach roadways width, alignment and grade.

d.) Design speed, posted speed, average daily traffic and percentage of truck traffic.

e.) Accident history on the structure.

f.) Traffic control required for initial construction of retrofit and for potential future repairs.

g.) Locations and characteristics of pedestrian facilities / features (if present).

3.) Features of the retrofit designs

a.) Placement or spacing of anchor bolts or dowels.

b.) Reinforcement anchorage and potential conflicts with existing reinforcement, voids, conduits, etc.

c.) Self weight of retrofit railing.

d.) End treatments.

e.) Effects on pedestrian facilities.

D. Evaluation of Existing Supporting Structure Strength for Traffic Railing Retrofits.

The Thrie Beam Guardrail and Vertical Face traffic railing retrofits are based on designs that have been successfully crash tested in accordance with NCHRP Report 350 to Test Level 4 or have been previously tested and then accepted at Test Level 4. The original designs have been modified for use with some of the wide variety of traffic railings and supporting deck and wing wall configurations that were historically constructed on Florida bridges. In recognition of the fact that the traffic railings and supporting elements were designed to meet the less demanding requirements of past AASHO and AASHTO Bridge Codes, modifications have been made to the original retrofit designs in order to provide for better distribution of vehicle impact force through the traffic railing retrofit and into the supporting bridge deck or wing wall. For Thrie Beam Guardrail Retrofit installations on narrow curbs and or lightly reinforced decks or walls, a smaller post spacing is used on bridge decks. In addition, through-bolted anchors are used for some Thrie Beam Guardrail Retrofit installations. For the Vertical Face Retrofit, additional longitudinal reinforcing steel and dowel bars at the open joints are used within the new railing.

Existing bridge decks and walls that will support a traffic railing retrofit must be evaluated to determine if sufficient strength is available to ensure that the retrofit will perform in a manner equivalent to that demonstrated by crash testing. Existing structures may contain Grade 33 reinforcing steel if constructed prior to 1952 or Grade 40 reinforcing steel if constructed prior to 1972. Use 90% of the ultimate tensile strength of these materials when determining the existing capacity for both tension and moment from traffic railing impacts (f s = 49.5 ksi for Grade 33, f s = 60 ksi for Grade 40). For existing structures containing Grade 60 reinforcing steel, only use the yield strength of this material (f s = 60 ksi). For bridges with varying spacings and sizes of transverse reinforcing steel in the deck or curb, the average area of transverse steel for the span may be used.

Existing cast-in-place reinforced concrete bridge decks shall be analyzed at a section through the deck at the gutter line for the appropriate FDOT traffic railing retrofit Standard Indexes using the following design values:

Traffic Railing Type | Structures Index No. | Design Std Index No. | Mg | Tu
Thrie-Beam Retrofit | 772, 776 & 777 | 471,475, & 476 | 5.8 | 4.7
Thrie-Beam Retrofit | 773 & 775 | 472 & 474 | 8.3 | 6.7
Thrie-Beam Retrofit | 774 | 473 | 9.7 | 7.9
Vertical-Face Retrofit | 782-785 | 481-483 | 12.9 | 7.5

M g (kip-ft/ft) - Ultimate deck moment at the gutter line from the traffic railing impact.

T u (kip/ft) - Total ultimate tensile force to be resisted.

The following relationship must be satisfied at the gutter line:

(T u / Φ P n )+ (M u / Φ M n) ≤ 1.0 | (Eq. 6-1)

Where:

Ø = 1.0

P n = A s f s (kips/ft) - Nominal tensile capacity based on the areas of transverse reinforcing steel in both the top and bottom layers of the deck (A s) and the nominal reinforcing steel strength (f s). This reinforcing steel must be fully developed at the critical section through the deck at the gutter line.

M u = Total ultimate deck moment from traffic railing impact and factored dead load at the gutter line. (M g+1.25*M Dead Load) (kip/ft/ft).

M n = Nominal moment capacity at the gutter line determined by traditional rational methods for reinforced concrete (kip-ft/ft). The bottom layer of steel must not be included unless a strain compatibility analysis is performed to determine the steel stress in this layer with the compressive strain in the concrete limited to 0.003.

Decks constructed of longitudinally prestressed, transversely post-tensioned voided or solid slab units generally only contain minimal transverse reinforcing ties. Retrofitting bridges with this type of deck will not be permitted after January 1, 2010. For these type bridges, the strength checks of the deck at the gutter line will not be required. Only Design Standards 475 or 480 series retrofits should be used to retrofit these bridges.

In addition to checking the existing deck capacity at the gutter line, the following minimum areas of reinforcing steel per longitudinal foot of span must also be satisfied unless a more refined analysis is performed to justify a lesser area of steel at these locations:

Minimum Steel Area (in2/ft) for Design Index No. (previously Structures Index No.)
Reinforcing Steel | 471,475 & 476 (772,776 & 777) | 472 & 474 (773 & 775) | 473 (774) | 481 - 483 (780 Series)
Transverse in top of curb beneath post: Grade 33 reinforcing | 0.32 | 0.40 | 0.40 | NA
Grade 40 & 60 reinforcing | 0.25 | 0.31 | 0.31 | NA
Vertical in face of curb for thickness "D" Grade 33 reinforcing | 0.20 | 2.25/(D-2)** | 2.65/(D-2)** | 3.30/(D-2)**
Grade 40 & 60 reinforcing | 0.20* | 1.80/(D-2)** | 2.10/(D-2)** | 2.60/(D-2)**
* 0.16 sq inches/foot is acceptable for D equal to or greater than 15-inches. ** Minimum area of reinforcing steel must not be less than 0.16 square inches/foot. Where: D (inches) = Horizontal thickness of the curb at the gutter line.

If the minimum areas of reinforcing in the curb given above are not satisfied, the following design values may be used for a refined analysis of the existing curb beneath the post for the Index 770 Series retrofits:

Traffic Railing Type | Structures Index No. | Design Index No. | Mp | Tu
Thrie-Beam Retrofit | 772, 776 & 777 | 471, 475 & 476 | 9.7 | 7.9
Thrie-Beam Retrofit | 773, 774 & 775 | 472, 473, & 474 | 12.0 | 9.9

M p (kip-ft/ft) - Ultimate deck moment in the curb at centerline of post from the traffic railing impact.

T u (kip/ft) - Total ultimate tensile force to be resisted.

The following relationship must be satisfied in the curb at centerline of post:

(T u / Φ P n )+ (M u / Φ M n) ≤ 1.0 | (Eq 6-2)

Where:

Ø = 1.0

P n = A s f s (kips/ft) - Nominal tensile capacity based on the areas of transverse reinforcing steel in both the top and bottom of the curb (A s)and the nominal steel strength (f s). This reinforcing steel must be fully developed at the critical section.

M u = Total ultimate moment in the curb from traffic railing impact and factored dead load at centerline of post (M p + 1.25*M Dead Load) (kip-ft/ft).

M n = Nominal moment capacity of the curb at centerline of post determined by traditional rational methods for reinforced concrete (kip-ft/ft). The bottom layer of steel in the curb must not be included unless a strain compatibility analysis is performed to determine the steel stress in this layer with the compressive strain in the concrete limited to 0.003.

The ultimate moment capacity of existing wing walls and retaining walls supporting the traffic railing retrofits must not be less than 9.7 kip-ft/ft for Index 470 Series retrofits (3'-1½" maximum post spacing) and 12.0 kip-ft/ft for Index 480 Series retrofits. Wing walls for Index 480 Series retrofits must also be a minimum of 5 feet in length and pile supported. For Index 480 Series retrofits only, wing walls that do not meet these criteria must not be used to anchor the ends of guardrail transitions and must be shielded by continuous guardrail as shown on the Design Standards. For both 470 and 480 Series retrofits, retaining walls must be continuous without joints for a minimum length of 10 feet and adequately supported to resist overturning.

An exception will be required for bridges or components of bridges that do not meet the preceding strength requirements. The potential for damage to the existing bridge deck or wing walls due to a very severe crash, such as that modeled by full scale crash testing, may be acceptable in specific cases. Contact the Structures Design Office for additional guidance and assistance in these cases.

### 6.7.5 Historic Bridges

A. Federal Law protects Historic Bridges and special attention is required for any rehabilitation or improvement of them. The Director of the Division of Historical Resources of the Florida Department of State serves as Florida's State Historic Preservation Officer (SHPO). The SHPO and FDOT are responsible for determining what effect any proposed project will have on a historic bridge. See the PPM Chapter 26.

B. Bridges that are designated historic or that are listed or eligible to be listed in the National Register of Historic Places present a special railing challenge because the appearance of the bridge may be protected even though the historic railing may not meet current standards. When a project is determined to involve a historically significant bridge, the District should contact the Structures Design Office for assistance with evaluating the existing bridge railings.

C. Original railing on a historic bridge is not likely to meet:

1.) Current crash test requirements.

2.) Current standards for railing height (a minimum of 32-inches for Test Level 4) and for combination traffic and pedestrian railings,

3.) Current standards for combination traffic and pedestrian railings, e.g. a minimum height of 42-inches and the limit on the size of openings in the railing (small enough that a 6-inch diameter sphere cannot pass.)

D. Options for upgrading the railing on historic bridges usually include the following:

1.) Place an approved traffic railing inboard of the existing railing, leaving the existing railing in place. This is sometimes appropriate when a pedestrian walkway exists on or is planned for the bridge.

2.) Replace the existing railing with an approved, acceptable railing of similar appearance.

3.) Remove the current railing and incorporate it into a new acceptable railing. This may be appropriate in rare instances where an existing railing is especially decorative.

4.) Design a special railing to match the appearance of the existing railing. It may not be necessary to crash test the new railing if the geometry and calculated strength equal or exceed a crash tested traffic railing.

### 6.7.6 Requirements for Test Levels 5 and 6 [13.7.2]

A. Consider providing a traffic railing that meets the requirements of Test Levels 5 or 6 when any of the following conditions exist:

1.) The volume of truck traffic is unusually high.

2.) A vehicle penetrating or overtopping the traffic railing would cause high risk to the public or surrounding facilities.

3.) The alignment is sharply curved with moderate to heavy truck traffic.

B. Contact the SDO for guidance if a Test Level 5 or 6 traffic railing is being considered.

### 6.7.7 Exceptions

A. In the rare event that an upgrade to the traffic railing on an existing bridge could degrade rather than improve bridge safety, during the early phases of a project consult the Structures Design Office about a possible design exception.

B. Factors to consider include the following:

1.) Remaining time until scheduled replacement or major rehabilitation of structure.

2.) Design speed and operating speed of traffic in the structure location, preferably no greater than 45 mph.

3.) Resistance to impact of the existing railing.

4.) Whether the structure ends are intersections protected by stop signs or traffic signals.

5.) Whether the geometry is straight into, along and out of the structure.

6.) Overall length of the structure.

7.) Whether traffic on the structure is one-way or two-way.

8.) Accident history on the structure, including damages to and repairs of the existing railing.

9.) Risk of fall over the side of the structure.

10.) Whether the bridge has an intersecting roadway or railroad track below.

11.) Whether a railing upgrade will further narrow an already narrow lane, shoulder or sidewalk.

12.) Load rating of the existing bridge.

13.) Special historic or aesthetic concerns.

C. Exceptions to the requirements of this Article must be approved in accordance with Chapter 23 of the Plans Preparation Manual, Volume I.

### 6.7.8 Miscellaneous Attachments to Traffic Railings (07/06) July 2006 - Revised per TDB C06-05.

A. Outside Shoulder Traffic Railings

Provide setback distances as shown in Figure 6-1 to non-crash tested discontinuous items, e.g. light poles, sign supports, traffic signal controller boxes, flood gauges, etc., that are attached to or located behind outside shoulder traffic railings. Discontinuous items located within these setback distances must be crash tested to, or accepted at, NCHRP Report 350 Test Level 3 minimum as attachments to traffic railings.

Fender access ladders are exempt from this requirement. Sign panels may be placed within the given setback distances, however the setback to the sign support may have to be increased to assure sign panels do not extend past the top inside face of the traffic railing. Motorist aid call boxes may be placed within the setback distances to allow for proper access and to meet ADA requirements, however the call box must not extend past the top inside face of the traffic railing.

Provide a setback distance of 5' -0" minimum from the face of outside shoulder traffic railings at deck or roadway level to non-crash tested continuous items, e.g. sound barriers, glare screens, fences, etc., that are attached to or located behind the railings. Sound barrier / traffic railing combinations located within this setback distance must be crash tested to, or accepted at, NCHRP Report 350 Test Level 4. Other continuous items located within this setback distance must be crash tested to, or accepted at, NCHRP Report 350 Test Level 3 minimum as attachments to traffic railings.

B. Median Traffic Railings

Do not place sign supports on median traffic railings unless AASHTO or FDOT standard design requirements for sign visibility cannot be met by placing the sign supports on the outside shoulder of the roadway or outside shoulder bridge or roadway traffic railing as described above. If sign supports must be attached to or placed within a median traffic railing, utilize a standard FDOT or ,other crashworthy detail specifically developed for that item as an attachment to a traffic railing. Discontinuous items located on median traffic railings for which no FDOT standard detail or design is available for must be crash tested to, or accepted at, NCHRP Report 350 Test Level 3 minimum as ,attachments to traffic railings.

Continuous items, e.g. glare screens and fences, located on median traffic railings must be crash tested to, or accepted at NCHRP Report 350 Test Level 3 minimum as attachments to traffic railings.

These requirements also apply to back-to-back outside shoulder traffic railings that are located so close together that the required setback distances as defined in paragraph "A" cannot be provided for both railings. See also the requirements stated in PPM Vol. 1, Table 2.11.2.

C. Existing Attachments to Traffic Railings

Evaluate existing attachments to traffic railings on existing facilities on a case by case basis as the facility is incorporated into a project. Evaluate the type of attachment and any crash history at a given location, number of attachments on the structure, ease of relocation, etc. to determine if the attachment needs to be removed or relocated. Large sign support structures should be relocated if possible.

COMMENTARY

These criteria are intended to improve crashworthiness of traffic railings and the miscellaneous attachments that are made to them while still meeting minimum standards for accessibility and roadway signing and lighting. No specific guidance on this issue is provided in LRFD or NCHRP Report 350. These criteria are based on findings and recommendations from ongoing research that began as a result of this lack of guidance.

These criteria are subject to being changed and or supplemented as further studies are completed.

### 6.7.9 Sidewalks (01/06) Jan 2006 Added Section per TDB C05-12.

Design bridges with sidewalks located behind traffic railings for the governing of the following two cases:

1. The initial design configuration with traffic load, pedestrian load, traffic railing and pedestrian railing loads present, or,

2. The possible future case where the traffic railing between the travel lanes and the sidewalk is removed and vehicular traffic is placed over the entire deck surface (no pedestrian loads present).

Commentary:

In the future, the sidewalk could be simply eliminated in order to provide additional space to add a traffic lane. For this case two options are viable:

1. Construct a second traffic railing at the back of the sidewalk instead of a standard Pedestrian / Bicycle Railing as part of the original bridge construction. A vertical face traffic railing is preferred for this application if ADA compliant handrails are required due to the grade of the sidewalk. Design the cantilever within the sidewalk deck area to resist vehicle impact forces and wheel loads.

2. Construct a standard Pedestrian / Bicycle Railing as part of the original construction of the bridge and then demolish it and replace it with a traffic railing when necessary. If the deck cantilever is adequately reinforced to resist vehicle impact forces and wheel loads, only the railing needs to be replaced. Dowel the new vertical steel into the deck.