LIOS Technology’s fibre optic linear heat detection system FibroLaser II® forms an integral part of the fire detection system at the Mrazovka tunnel, which is part of the Prague city ring road. This project as a whole was designed so as to yield maximum benefits in terms of road safety and, as construction progressed, it even came to incorporate new experience deriving from accident analysis of French and Austrian tunnels. All assessments indicate that the Mrazovka tunnel will rank among the safest underground roadway projects.