A real time information system (1) provides real time comprehensive information to drivers on roads. It has short-interval units (5) for mounting on a roadside barrier (B) at intervals of 100m and lower-density master control units (2) at 1km separations with more comprehensive displays. The short-interval units (5) communicate with a master unit (2) in a local area group. Local sensing of weather and traffic conditions at the master control unit allows advance warnings to drivers with a fast response time in an autonomous manner. The short-interval units have a saddle frame (50) for fitting to the top of a central reservation barrier (B) to allow low-level simple display of LED colour arrangements (66) in a coordinated linear pattern when viewed in sequence by a driver. A subset of the short-interval saddle units (5), such as every tenth one may additionally have a display screen (80).