Abstract: To investigate differences in evacuation environments in tunnels following fires involving electric vehicles (EVs) and internal combustion engine (ICE) vehicles, a case study is conducted on a tunnel project in Shanghai. Numerical simulation is employed to examine the heat and smoke generated by the combustion of EVs. Key environmental parameters, including tunnel visibility, temperature, and smoke distribution after fires involving the two vehicle types are systematically analyzed and compared under the effect of the existing exhaust system. The deterioration rate of the fire environment for EVs relative to ICE vehicles is quantified. The results demonstrate that: (1) EV fires significantly worsen the tunnel evacuation environment. When an EV catches fire, the relative deterioration rates of the hazardous visibility range length and the safe evacuation time within the tunnel are 58.3% and 51.8%, respectively. (2) A critical point exists at which the intensity of high-temperature hazards shifts between EV and ICE vehicle fires. Before this point, the environmental temperature of EV fires is lower; beyond it, the temperature significantly increases, reducing the temperature-safe evacuation time for EVs by at least 25% compared to ICE vehicles. Therefore, additional firefighting and rescue measures should be implemented promptly during the early stages of an EV fire. (3) In the event of an EV fire, the range where the smoke layer height is less than 2 m is 31.6% greater than that for an ICE vehicle. Moreover, the longitudinal spread length of the smoke increases by 30.8%, resulting in more extensive and severe smoke hazards.

Key words: urban tunnel, tunnel fire, electric vehicle, internal combustion vehicle, smoke extraction efficacy