Solar Message Signs (also known as Solar Portable Message Signs) are electronic traffic signs often used on roadways to give travelers information about upcoming special events. Such signs warn of traffic congestion, accidents, incidents, roadwork zones, or speed limits on a specific highway segment. They are seen in Left 4 Dead 2 in the Dead Center and Hard Rain campaigns, displaying messages to the Survivors about locations and objectives they should reach. They are simply environmental elements and props to give players a more realistic atmosphere and guide them to the main objectives; however, players can choose to ignore them completely if desired as they are not a necessary objective to complete like their counterpart, the Power Generator, is.