Curb and Guardrail Placement
On high-speed roads, avoid using guardrail-curb combinations due to the potential for vehicle vaulting. Where curbing is absolutely necessary to control drainage, the curb should be no higher than 4 inches and the guardrail should be semi-rigid to reduce potential deflection. The face of the guardrail and the face of the curb should align. The use of guardrail with curbs should be evaluated by a qualified engineer.