On 24th March 1999 a transport truck caught fire while driving through the Mont Blanc tunnel between Italy and France. Other vehicles travelling through the tunnel became trapped and fire crews were unable to reach the transport truck. The fire burned for 53 hours and reached temperatures of 1,000°C producing toxic smoke. Authorities compounded the problem by pumping air from the Italian side, feeding the fire and forcing poisonous black smoke through the length of the tunnel. A total of 39 people were killed. In the aftermath, major changes were made to the tunnel to improve its safety. This paper analyses the accident from a Services perspective, examining which critical services were in use (fire alert service, tunnel control service, ventilation service, etc), and which contributed in some way .The Safety Critical Systems Club (SCSC) Service Assurance Guidance v3.0 is used to guide the analysis and provide structure to the work, producing a service hierarchy map, criticality levels and identification of assurance needs. The improvements put in place after the accident are assessed to see the effect on the service assurance involved.