In general, the roadside terrain should be such
bility of highway engineers. Conventional con-
that it can be safely traveled by an out-of-control
struction materials for these devices include steel,
vehicle for a distance sufficient to bring the vehicle
concrete, aluminum, and wood. Fiber-reinforced
under control.
plastics are a recent addition, and this report will
The safety aspects of the roadside environment
deal with this material in detail in the following
deal primarily with the interaction of the vehicle
chapters. The selection of materials for these
with impact attenuation devices, such as guard-
safety elements must be judicious, taking into
rails, bridge rails, median barriers, utility poles,
consideration the modes of failure, impact resis-
sign posts, and embankment slopes. Their design,
tance, energy absorption, stiffness, durability, and,
construction, and maintenance are a major responsi-
of course, cost.
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