Risk assessment for tram traffic on tramway bridges

Promoted by many cities to meet the commute needs of their residents (for work, education, etc.), urban rail transport is a spatially expanding system. The safety of rail passengers and road users is one of the most important factors to consider when designing the infrastructure and assessing the operation of the urban tram system. One of the unsolved issues in the functioning of tram transport are sections of tramways with large longitudinal slopes. The article presents an attempt to use risk management for assessing the operational safety of tramways located on road sections with large longitudinal gradients. This particular problem occurs on a tram route in Gdansk. It runs along a street (partly on an overpass) with a gradient above 5% and a small horizontal curve. Risk was assessed using TRANS-RISK, a risk management method. In the first stage, a risk analysis was carried out using the Bow-Tie methods and error trees. The main risks of serious accidents on the analysed section of the tramway were identified. Three sub-concepts were used to assess risk: individual, societal and collective. Although not generally used for assessments of urban transport infrastructure, the latter was found most useful for assessing the safety of the analysed infrastructure. The results of the analyses and assessments helped to formulate design and maintenance principles for tram infrastructure located on sections with steep gradients.