 As the center of gravity and bumper heights of SUV’s and light trucks increased, pre-1990 guardrails that based their designs on low bumper height vehicles were no longer sufficient.Larger vehicles began to exhibit a tendency to rollover, vault, or rupture guardrails.Sicking led his team to develop a guardrail system that addressed the needs of all vehicle, increasing the rail mounting height, moving rail splices from the posts to the midspan, and increasing blockout depth by four inches.