sentences:  It consists of measuring (of both traffic and weather), control (e.g., variable speed limits), and signalling devices located in zones where driving conditions may vary, such as at the interchanges, viaducts, bridges, and zones where fog or strong wind are known to occur.The system uses variable-message signs to communicate changing driving conditions, possible restrictions, and other information to motorway users.In the Učka Tunnel there are 83 security cameras, 538 fire detectors, 39 fire hydrants, 74 emergency stations, and five vehicle emergency lay-bys; the speed limit is .