AGE-RELATED DISABILITIES THAT MAY IMPAIR DRIVING AND THEIR ASSESSMENT: LITERATURE REVIEW.

measures. Instructions for each task are given in audio form by means of an audio overlay card installed in the computer. Tests and scoring are computerized. Functions measured include: visual acuity—tested by means of differently oriented white Es against a black background; orientation indicated by moving a joystick. low-contrast acuity—same, but with light gray Es against a darker gray background. dynamic acuity—a moving letter E in one of four different orientations, to be identified by moving the joystick in the direction of the E's opening. target detection—a small white square in one of 10 locations is shown until the subject reacts by pushing a button on the joystick. form detection—an arrow in one of 10 positions and pointed in one of four directions is shown until the subject reacts, moving the joystick in the direction indicated by the arrow. motion detection—a square moves in one of four positions, starting from one of five positions; direction of motion to be indicated with joystick. simple reaction time—small white square appears in screen center for 500 ms, variable intertrial intervals; response is to push button on joystick. choice reaction time—arrow pointing in one of four directions appears in screen center, variable intertrial intervals; direction to be indicated by moving joystick. visual tracking—a small square appears in one of five positions; simultaneously a small cross appears in one of four positions with respect to square and moves toward the square; subject to push button on joystick exactly when cross reaches square. attention sharing—while cross moves toward square, arrow appears in one of four positions; subject performs visual tracking task as well as indicating direction of arrow. digit-span short-term memory—digit strings of increasing length are followed by three probe digits; subject deflects joystick to indicate whether a probe was in the string. AGE-RELATED DISABILITIES THAT MAY IMPAIR DRIVING AND THEIR ASSESSMENT 159 selective attention—arrow appears in one of four locations and oriented in one of four directions; subjects indicate, in alternate blocks of trials, orientation or location of arrow. perceptual speed—matrix of Es appears; all but one are vertical; subject indicates direction of opening in odd E. information processing—matrix of Es appears; one of four possible orientations is not represented; subject indicates unrepresented orientation with joystick. information processing—8-digit number appears in center of screen; around it are four more 8-digit numbers, one of which is the center stimulus rearranged; subject identifies it. embedded figures—four target screens are a circle with line, octagon, inverted triangle, and diamond; for each target screen there is a probe screen with complex pattern in which target shape is embedded; subject indicates corner of screen where target shape is embedded. Driving-related measures. Subjects use the joystick to "drive" through scenes presented on video. They are told that if they see a sign, "Route 22," they should turn right at the next intersection. static acuity—vehicle approaches a sawhorse; subject must detect obstacle. target detection—vehicle emerges from subject's blind spot and cuts across path; subject must detect by swerving or braking. form detection—form of car, boat, or plane appears at random locations; subject presses joystick button when form of car appears. angular motion detection—stimulus car rolls out of driveway on hill into path of subject's vehicle with increasing speed; subject must react. in-depth motion detection—vehicle ahead of subject's slows; no brake lights; subject must react. simple reaction time—in video, subject follows a car that puts on its brakes; must react. Also, using computer-generated stimuli, car ahead of subject's brakes; subject must brake. choice reaction time—subject's vehicle is in center of three lanes; one car ahead in each lane; brake lights on some of these come on. Subject must go left if two right cars brake, right if two left cars brake, and stop if all three brake. visual tracking—subject approaches intersection at same time as car coming from right, with stop sign at right. Other car may or may not slow to stop, or it may be too far away to matter. Subject must react appropriately. selective attention—subject drives along a section of roadway that includes unimportant distractions plus a hazard or stimulus requiring a reaction. Important stimuli and unimportant distractions occur together; subject must react to former. attention sharing—similar to the above, but hazards and direction signs compete for attention, and subject must react appropriately to both. perceptual speed—scenes are presented involving developing hazards which subject must anticipate and avoid. icon short-term memory—for each of five sign types (e.g., regulatory), a cluster of three signs is presented as target followed by four clusters in different corners of screen as AGE-RELATED DISABILITIES THAT MAY IMPAIR DRIVING AND THEIR ASSESSMENT 160 probe. Subject indicates matching type. Then five different probes are presented, one for each sign type; subject indicates corner that previously contained type-matching cluster. information processing—similar to icon short-term memory above. Target and probe screens are combined into one; subject matches central icon cluster. These tests will be field-evaluated in four states (one being California) during 1994-1997. They are all in the public domain, according to NPSRI. • Neurobehavioral Evaluation System (NES). A computer-based Neurobehavioral Evaluation System (NES) was developed for use in epidemiological field studies of human populations exposed to neurotoxic agents in the workplace or the general environment (Baker, Letz, Fidler, Shalat, Plantamura, and Lyndon, 1985). It is described here because the functional abilities assessed are, for the most part, the same ones tested in driver competency assessment. Table 9 gives an overview of the functions measured in the NES battery, the tests contained in it, and their administration time.