Information Processing
The concept of
positive guidance
is often
used as a guiding principle for providing information to drivers.
Positive guidance consists of creating and maintaining a driving
environment that has the following characteristics:- Motorists are provided with the maximum amount of useful visual information.
- Information is presented in such a way that it is prioritized in importance.
- Information is presented uniformly, allowing drivers to develop expectations about the location of information.
- Information is visible under most, if not all, environmental conditions.
If the principles of positive guidance are applied consistently,
drivers will subconsciously develop expectations about where to
seek information. In applying the concepts of positive guidance,
it is important to understand the demands that are placed on the
driver during the driving task. The driving task is made up of a
number of subtasks that require varying levels of time and cognitive activity.
The three most basic subtasks are control, guidance, and navigation.
These subtasks are explained in the following table.
Subtask | Explanation |
|---|---|
Control | Consists primarily of steering
control and speed control. |
Guidance | Consists of maintaining a safe
and efficient path relative to all factors in the roadway environment.
Some examples of actions included in the guidance subtask are car
following, passing, and response to traffic control devices. |
Navigation | Portion of the driving task
most directly affected by freeway guide signing. Consists of planning a trip from beginning to end and then
executing the trip plan. The navigation subtask can be broken down
into trip preparation and planning, and direction finding. Trip preparation
and planning can consist of anything from drivers using their own
mental map of an area to consulting maps or knowledgeable persons
in order to plan a trip. Direction finding occurs while drivers
are en route and attempting to reach their destinations. This portion
of the subtask involves interpreting direction guidance on signs
to obtain information about the appropriate path. |
Performance of these subtasks allows drivers to maintain their
positions in the lane and find their way to their destinations.
Drivers perform these subtasks continuously at various cognitive
levels, although the amount of attention and cognitive resources
allocated to each task may vary depending on the specific conditions
present at a given point and time. The following table describes
the characteristics of each of these subtasks.
Characteristics | Control Subtask | Guidance Subtask | Navigation Subtask | ||
|---|---|---|---|---|---|
Steering Control | Speed Control | Trip Preparation and Planning | Direction Finding | ||
Priority | High | High | Varies depending on conditions,
but usually intermediate between control and navigation | Performed pre-trip, so no demands
on driver while en route | Usually lowest of all subtasks, although demands
may increase in complex or unfamiliar situations |
Driver Level of Effort | Varies depending on geometrics | Varies depending on geometrics
and traffic | Higher than control subtask, with
more conscious decision-making necessary | Varies depending on driver familiarity
with route | Guide signs, Route signs, Street
Name signs, landmarks, etc. |
Information | Vehicle response characteristics, relative
position of vehicle | Vehicle braking and acceleration characteristics, road
conditions ahead of driver | Traffic conditions, road geometry, weather
conditions, and other information that impacts the road environment | Location or origin and destination,
and physical or mental map of alternative routes | Guide signs, Route signs, Street
Name signs, landmarks, etc. |
Demand on Drivers | Usually low because subtask is
overlearned | Greater than steering since driver
must look farther down the road | Varies depending on the driver’s
previous experiences and prior knowledge | Usually low | Usually low, except in unusual circumstances |