This work presents a study to improve the safety of experimental autonomous vehicles in the Heudiasyc laboratory. This work presents risk analyses showing that the use of our vehicles involves significant risks during experiments, and that integrating an Independent Safety Component called Safety-Bag in the vehicle architecture can significantly reduce these risks. The Safety-Bag carries out the on-line verification of safety necessities by checking the vehicle's current state with safety rules and taking or disabling actions to ensure a safe behavior. In our work, we present and we apply two methods for risk analysis (FMEA and HazOp-UML) to design these safety necessities in the case of experimental autonomous vehicles. We also present the validation of two safety necessities through fault injection experiments with a robotized Fluence vehicle and a vehicle in the loop testbed.