Guide signs require simplicity and clarity because drivers of moving vehicles are unable to read lengthy or complicated messages on signs. For this reason, sign messages should not exceed three lines.
On freeways, high traffic speeds demand that the number of signs be limited to those absolutely essential for the guidance of the motorist. Freeway exits are identified by the exit number, the route number or the name of the intersecting road. Certain additional messages may be provided where justified.
In rural areas signs may be installed to direct travelers to services such as roadside rests, gas, food and lodging.