A deluge fire protection system for tunnels having vehicle traffic including a main water supply pipe and a horizontal spray nozzle arrangement. The horizontal spray nozzle arrangement includes a nozzle device having an inlet portion defining an internal diameter and an external nominal diameter. The horizontal spray arrangement includes a coupling arrangement between the main water supply and the nozzle device. The coupling arrangement defines a multi-direction flow path between the main water supply and the nozzle device. The multi-direction flow path has an effective length of at least eight times a diameter of the inlet portion, and a cross-sectional area along the effective length greater than the cross-sectional area defined by a diameter of the inlet portion of the body of the nozzle device. The coupling arrangement provides for water delivery to the nozzle device at a working pressure ranging from about 10 psi. to about 30 psi.