Guardrail and median barrier design information is presented which will permit the safest highways consistent with current state-of-the-art barrier technology. Since guardrail and median barrier installations are hazardous in themselves, emphasis is placed on reducing the number of installations to those which can be clearly justified. The design procedure presented involves two steps: (1) determination of points and length of need for the installation, and (2) selection and layout of appropriate guardrail or median barrier system. Specific warrants for an installation are determined from the roadway properties (such as shoulder embankment geometry) and the location and type of roadside obstacles. Guardrail and median barrier designs evaluated by full-scale crash tests and satisfactory service performance are presented together with a selection procedure. Median barrier warrants are determined by median width and traffic volume. These warrants are based on ran- off-the-road and across-the-median type of accident statistics and dictate use of installation only where accident severity would be less for a vehicle's striking the barrier than permitting it access to the screened area. Procedures for examining, classifying and delineating servicing action for existing guardrail and median barrier installations are described.
Samenvatting