There are many types of portable electronic message boards. These are usually used on roads, by contractors to divert traffic or display warning information to road users.  Some are simple arrow boards which will delivery traffic into a merging lane or away from a road obstacle. Others are more sophisticated and can display a message with scrolling text. 

Light boards can be seen at day or night. They are controlled by a controller in the cab, so you do not need a separate controller, laptop or other type of controller to change the displayed messages.  The LED displays have a very long life around fifty thousand hours or more.  The brightness will automatically change according the day or night conditions.  This helps to save energy and prevent.