The contribution from asphalt pavement to road tunnel fire risk

This study investigates fire safety in road tunnels, focusing on the contribution of road pavements and the impact of their combustion on evacuation conditions during fire incidents. Asphalt, a material widely used in road pavements, can contribute to fire development. In particular, its combustion may increase fire load, smoke emissions, and the release of toxic gases, complicating self-evacuation efforts. To address these concerns, some European countries require or recommend the use of concrete for road tunnel pavements, given its non-combustible properties. The objective of this research is to assess the contribution of asphalt pavement to road tunnel fire risk. Specifically, the study evaluates the effective heat release rate (HRR) of burning asphalt and employs a risk-based design approach to analyze hazard flow scenarios. Two scenarios are considered: a 50 MW fire in a 999-meter-long tunnel with asphalt pavement and one with concrete pavement. The methodology combines an analysis of previous experiments on the fire reaction of various asphalt mixtures with computational fluid dynamics (CFD) simulations to estimate the additional risks posed to evacuation in tunnels with asphalt pavements. The results indicate safer evacuation conditions, with fewer fatalities, in scenarios involving concrete pavements.