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Testing criteria and test levels for bridge railings are the same as previously discussed for roadside barriers (Art. 6.4). The FHWA maintains a list of designs that have been tested to NCHRP Report 350 levels, as well as designs that were tested to earlier guidelines and have been assigned an equivalent Report 350 test level. […]

The first step in an upgrading project is to identify potentially deficient systems. Bridge railing designs prior to 1964 are particularly suspect. Strength and performance should be documented. Verify critical details such as base plate connections, anchor bolts, material (strength, toughness, and condition), welding details, reinforcement development, etc. Open-faced railings may cause snagging. Curbs or […]

Bridges should provide a full, continuous shoulder that maintains uniform clearance with approaching roadside elements. However, if the bridge is narrower than the AASHTO Designation Test Level: Nominal Barrier Height: Maximum Dynamic Deflection: Remarks: This proprietary portable barrier system is suitable for both permanent (unbalanced traffic flow) and temporary applications. It is composed of a […]

Bridge railings are longitudinal barriers intended to prevent vehicles from running off the edge of a bridge. A metal post-and-rail system, a concrete safety shape, and various combinations have been used. Bridge railings are attached to the structure and designed to have minimal deflection under impact. The AASHTO Standard Specifications for Highway Bridges require that […]

Either roadside barriers or median barriers may be appropriate for sloped medians, depending on conditions. If a relatively flat median (slope of 1:10 or flatter) free of rigid objects is available, a median barrier can be placed at the center. When such desirable conditions are not available, some additional guidelines should be considered. Figure 6.36 […]

Transition sections are used between adjoining median barriers having significantly different deflection characteristics, between a semirigid median barrier and a rigid barrier (such as a bridge rail), and in similar situations. The transition sections should provide impact performance similar to standard sections, and emphasis should be placed on designs to avoiding vehicle snagging. Structural details […]

Median barriers, similar to roadside barriers, should be introduced and terminated with safety in mind. Openings or breaks in barriers should be kept to a minimum to negate the need for end treatments. Where openings are required, shield barrier ends or, if the median SGM04a (with non­steel blocks) TL-3 W6x9 6ft-3 in Two steel W […]

Like roadside barriers, median barriers can be classified as flexible, semirigid, or rigid as indicated in Table 6.7. Figures 6.26 through 6.35 show details of these various types of median barriers and factors to be considered in selection and application. Additional comments on several of the systems follow. In many of their characteristics they are […]

Table 6.6 provides a checklist that can be used to review existing barrier installations and determine adequacy for either structural or functional (design or placement) causes. Factors to be considered in determining the scope and extent of upgrading include the nature and extent of the deficiency, past accident history, and the cost-effectiveness of the recommended […]

The total length of a longitudinal barrier needed to shield an area of concern is referred to as the length of need. Figure 6.23 illustrates the variables that must be con­sidered, particularly the runout length LR and the lateral extent of the area of concern LA. The runout length is the theoretical distance needed for […]