Flexible rail for floor level guardrail systems is made from polypropylene copolymer so that it flexes and then rebounds to its original position upon impact. By flexing to absorb the impact, it reduces damage to the vehicle, floor, and the guardrail itself on direct impacts or glancing blows. Rails mount into end posts, corner posts or middle posts that are anchored to the floor and have rubber dampeners to help absorb the energy of an impact.