SAFETY ANALYSIS OF NATURAL GAS VEHICLES TRANSITING HIGHWAY TUNNELS

A safety analysis was performed to assess the relative hazard of compressed natural gas (CNG) fueled vehicles traveling on various tunnels and bridges in New York City. The study considered those hazards arising from the release of fuel from CNG vehicles ranging in size from a passenger sedan to a full size 53 passenger bus. The approach used was to compare the fuel hazard of CNG vehicles to the fuel hazard of gasoline vehicles. The risk was assessed by estimating the frequency of occurrence and the severity of the hazard. The methodology was a combination of analyzing accident data, performing a diffusion analysis of the gas released in the tunnel and determining the consequences of ignition. Diffusion analysis was performed using the TEMPEST code for various accident scenarios resulting in CNG release inside the Holland Tunnel. The study concluded that the overall hazard of CNG vehicles transiting a ventilated tunnel is less than the hazard from a comparable gasoline fueled vehicle. 134 refs., 23 figs., 24 tabs.