Some principles for communicating with drivers through the use of variable-message displays.

It must be ascertained whether motorists have learned the message content of signs and responded with appropriate behaviour. According to the studies cited and current research, motorists tend to disregard the signs if the signs of the signed information blends into the background and if the regulations of certain traffic movements are in conflict with perceived time savings. Respectively, a brief discussion follows on (1) interpretation; (2) reliability; (3) advance notice; and (4) prominence.