Vehicle fires in road tunnels present a serious risk to the structure of the tunnel. In many countries it is mandatory for road tunnels to be protected by Linear Heat Detection. Maintenance access tunnels are often found in all manner of major infrastructure projects. They are infrequently used and can be damp, humid, and hot. Signaline HEAT Linear heat detection performance is unaffected in these enviornments and makes for a perfect detection solution in unmanned areas.