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Utility supports represent a serious hazard that accounts for about 10 percent of all fixed-object fatal crashes. Elimination, relocation, and burying the lines are preferred options. Increased spacings or multiple use may reduce the number of poles. A breakaway device has been tested and may be considered for vulnerable locations. A breakaway device for utility […]

Supports for traffic signals are not usually of the breakaway type, because of the potential consequences of the loss of the signal at an intersection. Supports in the clear zone should be shielded. Call boxes can often be located behind existing barriers, but a breakaway support is an option. The call box should be securely […]

Breakaway supports for luminaires are usually a cast-aluminum transformer-type fran­gible base, a slip base, or frangible couplers. These devices have been developed to activate when loaded in shear by impacts at a bumper height of about 20 in (500 mm). If the supports are located so that they may be impacted at a greater height, […]

Roadway signs include overhead signs, large roadside signs (area over 50 ft2 or 5 m2), and small roadside signs. Overhead signs include sign bridges and cantilevered signs. Their supports are generally too large to adapt to a breakaway design. When possible, install overhead signs on existing bridges or other structures. Otherwise, supports within the clear […]

Approximately 15 percent of all fixed-object fatalities involve sign and luminaire supports or utility poles. The options available to the highway engineer to improve on this recordare similar to those presented earlier: remove or redesign, relocate, use a breakaway device, shield, or delineate. Although it is desirable to have an unobstructed roadside, it is not […]

The drainage system should be designed, constructed, and maintained with considera­tions for both the hydraulic function and roadside safety. (See Chap. 5.) In addition to channels, elements of the system include curbs, cross-drainage (transverse) structures (pipes and culverts), parallel drainage structures, and drop inlets. The following three options, listed in order of preference, are applicable […]

Except for flat roadsides, a motorist leaving the roadway may encounter a foreslope (negative grade such as on an embankment), a backslope (positive grade such as in a cut section), a transverse slope (such as caused by an intersecting side road), or a drainage channel (change from negative to positive grade). Foreslopes parallel to the […]

The clear roadside concept has a direct and obvious application to the selection of slopes and design of drainage features such as ditches, curbs, culverts, and drop inlets. A traversable, unobstructed roadside zone should extend beyond the edge of the driving lane for an appropriate distance so that the motorist can generally stop or slow […]

The roadside is defined as that area beyond the traveled way and shoulder. Thus, road­side safety is concerned with treatments that minimize the likelihood of serious injuries when a vehicle runs off the roadway. Roadside safety design has received particular emphasis since the 1960s. The increased awareness of its importance and the development of improved […]

Roger L. Brockenbrough, PE. President R. L. Brockenbrough & Associates, Inc.Pittsburgh, Pennsylvania One of the most important and most challenging aspects of highway engineering is designing to enhance life safety. This chapter focuses on roadside safety, which encompasses the safety of vehicles that leave the roadway and shoulder. This material is based largely on the […]