CHICAGO (AP) — Illinois officials say a safety feature that slows trains traveling dangerously fast is one of the last components that must be installed before a Chicago-St. Louis high-speed line becomes operational. Springfield’s State Journal-Register cites a state Department of Transportation spokesman as saying the system’s required under an agreement with the U.S. government. The GPS-reliant system was in the news recently following an Amtrak derailment in Philadelphia. Safety experts say the system could have helped prevent the crash that killed eight. Positive train control is already installed on a central Illinois section of the line. Mike Stead is a manager of an Illinois Commerce Commission safety program. He says once the system’s installed, the Chicago-St. Louis line will be among the first major routes with positive control outside the Northeast.