When process disturbances occur, workers on the Tunnel Boring Machine (TBM) will need to operate outside safe zones, reducing or eliminating the safety barrier ‘distance’ between them and potential sources of risk. Consequently, disturbances have a higher risk potential than regular TBM operations. By comparing the risks of registered process disturbances with regular TBM process, we try to predict accident scenarios. The exposure risk is defined by the exposure time and the injury severity. Exposure times have been determined from case histories, where on average 11% of the construction period is attributed to disturbances. The potential number of casualties, including less common incident scenarios, have been determined using an accident scenario building toolkit. We find that factors that contribute most to occupational risk reduction are the (correct) use of available risk prevention measures, correct design of safety barriers and making these barriers available to personnel, as well as detailed planning of procedures such that specific tasks are performed in a uniform and predetermined manner.@en