Implementing Graphic Route Information Panels ( GRIPs ) in the United States

decisions. Introduction Providing dynamic roadside information to travelers for improved decision making is a key element of congestion management.1 Currently, this is achieved on highways through the deployment of electronic variable message signs (VMS). The theory behind the use of VMS is that enabling drivers to make better route decisions will lead to less congestion delay and better utilization of the road network. However, these signs have limited display capacities. VMS are usually restricted to three lines of up to 20 alphanumeric characters and no more than two displays within a message cycle in order to convey a single thought.2 Under normal driving conditions at 120 km/hr (≈ 75 mph), drivers have only 5 to 6 sec. to interpret signs. As a result, given the complexity of roadway environments and traffic patterns, text-based electronic signs are simply unable to present all relevant information necessary for drivers to make efficient route decisions.3 Graphic Route Information Panels (GRIPs) represent the next step in dynamic traveler information sign evolution. Based on the principle that graphics are processed faster than written language, GRIPs improve on traditional text-based VMS by providing drivers with real-time, color-coded congestion information in a graphical format for specific segments of the local transportation network. Trial deployments and studies of GRIPs originated in Japan in the 1980s and have taken place in Australia, China, Japan, and the Netherlands. The basic GRIP is composed of an inactive component and an active component. The inactive component is a reflective sheet containing a road network outline, road or landmark names, and a driver orientation arrow. The active component consists of a twoor threecolor light-emitting diode (LED) array that lights up to display the congestion levels of the specific network links outlined in the inactive component. Adhering to the traditional traffic color scheme, many international GRIPs use green to represent light or free-flow traffic, yellow for medium congestion, and red for heavy congestion or stop-and-go traffic. Others use a two-color scheme of yellow/orange for medium congestion, red for heavy congestion, and black (unlit LEDs) to indicate that the traffic situation is normal. The road network outlines displayed in GRIPs can vary from an all-encompassing regional map to a single roadway. Advanced GRIPs may also contain additional information features, such as travel times between exits, accident locations, and lane closures.