Andrew W. Gellatly

SPEECH RECOGNITION AND AUTOMOTIVE APPLICATIONS: USING SPEECH TO PERFORM IN-VEHICLE TASKS

An experiment was conducted to investigate the effects of automatic speech recognition (ASR) system design, driver input-modality, and driver age on driving performance during in-vehicle task execution and in-vehicle task usability. Results showed that ASR system design (i.e., recognition accuracy and recognition error type) and driver input-modality (i.e., manual or speech) significantly affected certain dependent measures. However, the differences found were small, suggesting that less than ideal ASR system design/performance can be considered for use in automobiles without substantially improving or degrading driving performance. Several of the speech-input conditions tested were statistically similar, as determined by the dependent measures, to current manual-input methods used to perform identical in-vehicle tasks. Further research is warranted to determine how extended exposure to, and use of, ASR systems affects driving performance, in-vehicle task usability, and driver opinion compared with conventional manual-input methods. In addition, the research should investigate whether prolonged exposure to, and use of, ASR systems results in significant improvements compared to the current research findings.

Influence of truck driver eye position on effectiveness of retroreflective traffic signs

The amount of light reflected from a retroreflective traffic sign decreases with an increase in the observation angle—the angle between the headlamp, the sign, and the eyes of the driver. Mainly because of the increased seated eye height of truck drivers, the actual observation angles are greater for them than they are for car drivers. Consequently, there is concern about the impaired night-time detection and legibility of retroreflective signs for truck drivers. The present study evaluated the relative amount of light reaching drivers of different types of vehicle by using survey data collected in 1989 by the Transport and Road Research Laboratory (TRRL) in England. The TRRL data included driver eye heights and headlamp mounting heights for 445 vehicles. The present analysis considered three sign locations on a straight roadway: left shoulder, centre, and right shoulder. Two viewing distances were included: 152 m (500 feet) (typical of a sign-legibility distance), and 305 m (1000 feet) (typical of a sign-detection distance). The analysis considered both the differential amount of illumination impinging on the signs from headlamps of trucks and cars, as well as the differential amount of the light reflected from the signs in the direction of truck drivers and car drivers. The main results are that for the viewing distance of 152 m, the amount of light reaching a truck driver can be as low as 25% of the light reaching a car driver; the corresponding percentages for the viewing distance of 305 m are as low as 68%. These reductions were then related to the expected effects on sign legibility and detection. The results imply that the increased eye height of truck drivers could have a major effect on the legibility of retroreflective traffic signs, but only a modest effect on their detection.

Reaction times to high-contrast brake lamps

University of Michigan, Ann Arbor, Industry Affiliation Program for Human Factors in Transportation Safety

Visual Aiming of European and U.S. Low-Beam Headlamps

This study evaluated the effect of the sharpness of the cutoff (the transition between the lighter and darker portions of the beam) of low-beam headlamps on visual vertical aiming. Out of ten lamps tested, seven had a U.S. type beam pattern and three had a European type beam pattern. Twenty younger and middle-aged subjects of both sexes, along with an experienced lamp aimer, were asked to adjust the aim of the lamps in such a way that the cutoff of the beam was coincident with a horizontal line on a vertical surface. The subjects were instructed to make the alignment using the illumination gradient to the right of vertical for the U.S. type lamps and to the left of vertical for the European type lamps. Each person aimed each lamp ten times. There were two main results. First, the location of the perceived cutoff was near the location of the maximum contrast between adjacent vertical parts of the beam pattern. Second, the variability of the aiming performance was systematically related to the magnitude of the maximum contrast.