A current state of the knowledge is presented with respect to service requirements for bridge rail systems. Examination of accident information shows that approximately 20% of fixed-object fatal accidents involve bridge barrier rail systems. The hazardous conditions identified are: (1) vehicle penetration of bridge or approach barrier rails, (2) snagging of a vehicle by components of bridge or approach barrier rails, (3) vehicle collisions with the approach end of bridge or approach barrier rails, and (4) collisions in which a vehicle is redirected by a railing system. Full- scale dynamic tests conducted on new and modified barrier railing concepts indicate that the first three hazardous conditions can be eliminated by providing adequate strength, by attention to details of design, and by providing a satisfactory transition between approach rails and bridge rails. The Texas transportation institute produced a simple mathematical model to predict the reactions of a vehicle-guardrail collision. A barrier rail capable of lateral displacement produces a lower impact force than a rigid barrier, with a corresponding reduction in the severity of damage to a colliding vehicle. Design criteria for rigid and flexible railing systems can be developed by employing the rational analytical approach and other information presented. Careful consideration must be given to providing adequate connections. To assist the practicing highway engineer in the design of a bridge barrier rail system, ten service requirements are defined and listed. However, design criteria must be subject to continual review and revision.
Abstract