Armed with a handful of anecdotal case reports of brain injuries, the U.S. Congress has recently proposed legislation to regulate the level of G forces of roller coasters. However, high G forces are well tolerated during many activities and, therefore, are a poor measure for the risk of brain injury.

Yes, roller coaster G-forces are generally safe for the healthy general public because they are engineered to stay well within the limits of human physiological tolerance. Most modern coasters subject riders to positive G-forces (pushing you into your seat) ranging from 3G to 4.5G, which is comparable to what astronauts feel during a shuttle launch. While these forces can cause "greyouts" (a brief loss of color vision) if sustained, engineers design tracks so that the highest forces last only for a fraction of a second, preventing blood from pooling too far from the brain. Negative G-forces (the "airtime" feeling) are kept even lower, usually not exceeding -1.5G, to prevent discomfort. For perspective, the human body is incredibly resilient; even a strong sneeze can generate nearly 3G. Safety is ensured through strict ASTM (American Society for Testing and Materials) standards that mandate "jerk" limits—the rate at which G-forces change—to prevent neck and back strain. However, because these forces place stress on the heart and spine, individuals with pre-existing cardiac conditions, high blood pressure, or recent surgeries are always advised to follow the posted health warnings at the ride entrance.