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This report presents data using multiple-choice questionnaires to learn how drivers respond to traffic information in the form of advisory messages. Two experiments, comprising 112 participants, were conducted using the same technique and yielding similar results. The traffic information messages presented to participants varied in three respects; quantitativeness of information, imperativeness of advice, and timeliness of information. Two additional factors were examined; the amount of traffic congestion stated to be directly observable on the route and the stated accuracy of messages received in the past. Results obtained from the questionnaires indicate that the structure of the traffic message did influence the driver behavior. The propensity to depart from the planned route ahead of schedule was greater when respondents had; few exit options remaining, been told traffic levels were high, received accurate traffic information in the past, and had received messages which contained quantitative and/or imperative information. Traffic controllers with this knowledge of driver behavior could act to further reduce trip times and congestion by using the control tools currently available to them. The major conclusion we can draw from this study is that when possible and appropriate, advisory messages should contain accurate, timely, quantitative and imperative information.

Drivers often perform tasks alone or in combination that don't relate to control of their vehicle. This experiment evaluates the impact on simulated driving of performing non-driving tasks. The results showed that some of these tasks significantly degraded driving performance. The task that required drivers to use the map device caused the greatest problem. In addition, older drivers performed less well than younger drivers. The study shows objective reasons for evaluating the trade-offs between maximizing traffic safety and providing drivers with information that requires a high degree of visual attention. In the experiment, drivers performed the following secondary tasks alone, as pairs, or all three simultaneously: talking on a simulated cellular telephone, finding an object in an enclosed container, and using a special radio with head-up map and text displays. The experiment required drivers to maintain speeds of 25 to 30 miles per hour, keep the car centered in their traffic lane, and respond quickly to the appearance of simulated brake lights. Researchers divided subjects into four groups of 10 members each: young females and males with an average age of 31 and older females and males with an average age of 70.