Following the 1994 San Marino Grand Prix, which saw the deaths of Ayrton Senna and Roland Ratzenberger, the FIA formed an Expert Advisory Safety Committee to research and improve safety in motor racing. Chaired by Formula One medical chief Professor Sid Watkins, the committee worked with the Motor Industry Research Association to strengthen the crash resistance of cars and the restraint systems and to improve the drivers personal safety. The recommendations of the committee led to significantly more stringent crash tests for racing vehicles, new safety standards for helmets and race suits, and the eventual introduction of the HANS device as compulsory in all international racing series. The committee also worked on improving circuit safety. This led to a number of changes at motor racing circuits around the world, and the improvement of crash barriers and trackside medical procedures.