Objective

The work zone (WZ) is a key location of attempts to improve the California highway transportation system. It is also the location of a disproportionate number of collisions. Safety authorities are thus naturally interested in pursuing means of improving safety in this setting. The changeable message sign (CMS) is potentially a useful tool on California highways. Messaging in this medium can be used to enhance safety and reliability on the highway by assisting motorists to gracefully alter travel patterns around the WZ and to reduce delays that presently spring from this cause. The CMS is one of a series of ITS tools that has the potential to assist in these efforts. But recent study of CMS effectiveness has revealed a number of areas requiring additional research. This proposal directly attacks such questions both in the context of the WZ and for general use. Results of the studies proposed should enable CMS users to more nearly optimize CMS effectivity, thereby making meaningful improvements in safety, reliability and performance.

Methodology

In the first year, the proposed research consists of (1) a literature review covering such topics as CMS guidelines, visibility, legibility, attention, and serial text messaging, and (2) a laboratory study of the ability of human observers to discern CMS-like messages while engaged in a task like lane keeping. We plan to study the speed and accuracy with which CMS-like messages can be acquired as a function of various manipulations of the structure and presentation qualities of the CMS messages. Speed is measured in a reaction time task, and accuracy is measured in a forced-choice task where text of a CMS message is briefly displayed and the observer must identify from a list of many possible messages the one that was presented. Accuracy is estimated by percent correct identification.

Observers, include both young adults and older drivers, will be positioned a fixed distance from the CMS-like display, structured to appear the same size as it would at the specification distance for 55 mph travel. The display color and font will simulate contemporary CMS design. A lane-keeping-like task will be presented and the observer will have to keep his 'vehicle' within lane boundaries while at the same time looking for messages on signs at the 'side' of the road. The sign will increase in size over time as if the observer were passing by it at the design speed of 55mph.

At the end of the first year, we plan to deliver a set of suggested guideline additions (to complement existing MUTCD guidelines) based on the results of studies conducted in that year. In the second year, we propose to test one or more of these suggested guidelines in the field. We would choose a CMS that is near permanent loops that allow traffic speed and volume monitoring. Different message versions would be tried while traffic was monitored, allowing measurement of the effect of the proposed guideline.