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4 in this research was the lateral encroachment distance neces- Traffic characteristics, including speed, vehicle mix, and sary for a vehicle to stabilize after impacting a curb at high- volume. way speeds. Roadway alignment. Facility type (e.g., parkway, arterial, or freeway). Cross-section (e.g., median, number of lanes, shoulder, PROJECT OBJECTIVES and roadside). The primary goal of this research was to develop design guidelines for using curbs and curbbarrier combinations on There were essentially two complementary objectives of roadways with operating speeds greater than 60 km/h. The this research: (1) determining the safety effectiveness of dif- guidelines took into account the following factors: ferent types of curbs and (2) determining the proper combi- nation and placement of curbs and barriers such that traffic Curb type, height, configuration, material, vertical reveal, barriers remain effective. and distance from edge of traveled way. The first phase of the project involved an in-depth review Purposes of curb: aesthetics, hydraulics, delineation, of published literature in order to identify information perti- access control, pedestrian refuge, protection of local envi- nent to the design, safety, and function of curbs and curb ronment, water quality, and historical preservation. barrier combinations on roadways with operating speeds For curbbarrier combinations, barrier type (i.e., flexi- greater than 60 km/h (37 mph). Computer simulation meth- ble, rigid, and semirigid), height, configuration, distance ods were used in a parametric investigation involving vehi- from edge of traveled way, distance from curb, and end cle impact with curbs and curbbarrier combinations to deter- treatment. mine which types of curbs are safe to use on higher-speed Roadside characteristics, including the surface behind roadways and to determine proper placement of a barrier with curbs, such as grass, sidewalks, pavement, or sideslope. respect to curbing such that the barrier remains effective in Environment. safely containing and redirecting the impacting vehicle. The Area characteristics (e.g., suburban or rural). results of the study were then synthesized and guidelines for Climatic conditions (e.g., snow or heavy rains). the use of curbs and curb-and-barrier systems were developed.