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
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.