There is a joint regime to manage passenger safety. LUL retains responsibility for passenger safety, and its safety case must be accepted by the Health & Safety Executive (HSE). The Infraco is generally liable if one of its assets is delivered to LUL in an unsafe state. Each Infraco has its own Safety Case that it must comply with, but it must also co-operate with LUL to allow it to meet its statutory Safety Case responsibilities. The HSE takes high level assurance that the Infracos are adhering to health and safety law from the regime imposed by London Underground and the existence of a range of industry standards to regulate the work of the Infraco. In 2003-04, all Infracos maintained compliance with the Safety Case requirements and safety outcomes are consistent with recent years, with roughly two derailments per year prior to, and under, the PPPs - see Case example 4 on page 40.