Biomedical subjects

Samuel G Charlton

Publications and source records attributed to Samuel G Charlton.

5 recordsLinked to original sources

PubMed2007

The role of attention in horizontal curves: a comparison of advance warning, delineation, and road marking treatments.

Horizontal curves have been recognized as a significant safety issue for many years, a more important factor than road width or sight distance. The research literature suggests that driver errors associated with horizontal curves result from three inter-related problems: failures of driver attention, misperceptions of speed and curvature, and poor lane positioning. To examine the roles of attentional, perceptual, and lane placement factors in driver behaviour at curves, two groups of curve treatments were identified for testing with a driving simulator. The first group of treatments consisted of four combinations of warning signs designed to alert drivers to the presence of curves and produce a reduction in curve approach speeds. The second group was comprised of several types of road markings designed to affect drivers' speed and lane position as they drove through curves. The results indicated that advance warning signs by themselves were not as effective at reducing speeds as when they were used in conjunction with chevron sight boards and/or repeater arrows. Of the road marking treatments only rumble strips produced any appreciable reductions in speed. A herringbones road marking was found to produce significant improvements in drivers' lane positions, effectively flattening the drivers' paths through the curves. A treatment combining the herringbones treatment with chevron and repeater arrow signs produced both a reliable reduction in speed as well as improved lane positions. The results are interpreted as evidence that treatments that highlight perceptual cues are the most effective means of moderating drivers' curve speeds.

Acceleration↗

PubMed2006

Explicit and implicit processes in behavioural adaptation to road width.

The finding that drivers may react to safety interventions in a way that is contrary to what was intended is the phenomenon of behavioural adaptation. This phenomenon has been demonstrated across various safety interventions and has serious implications for road safety programs the world over. The present research used a driving simulator to assess behavioural adaptation in drivers' speed and lateral displacement in response to manipulations of road width. Of interest was whether behavioural adaptation would occur and whether we could determine whether it was the result of explicit, conscious decisions or implicit perceptual processes. The results supported an implicit, zero perceived risk model of behavioural adaptation with reduced speeds on a narrowed road accompanied by increased ratings of risk and a marked inability of the participants to identify that any change in road width had occurred.

Acceleration↗

PubMed2005

Conspicuity, memorability, comprehension, and priming in road hazard warning signs.

This study assessed driver reactions to 16 road hazard warning signs of various formats by projecting life-sized video of road scenes to drivers in a driving simulator. A range of measures, including attentional and search conspicuity, implicit and explicit recognition, dynamic and static comprehension, and sign priming were collected. Of the signs tested, road works and school warning signs were most often detected, remembered, and understood. Slippery surface warnings were associated with some of the lowest detection and comprehension rates. The effectiveness of the different formats depended on the type of hazard sign. In the case of road works warnings, a flashing variable message format was only slightly more conspicuous than the large dimension format, equal in comprehensibility, and perhaps somewhat worse in terms of memorability. For the school warnings, however, the flashing variable message format appeared to convey a greater sense of potential hazard, produced superior search conspicuity and priming, and was equal in terms of memorability and comprehensibility. The range of measures worked well as a whole with the two measures of conspicuity and the measure of static comprehension showing the greatest consistency.

Accidents, Traffic↗

PubMed2004

Perceptual and attentional effects on drivers' speed selection at curves.

This paper describes an experiment comparing the relative effectiveness of various types of warnings on drivers' speed selection at curves. The experiment compared three types of curve warnings across three different curve types in a driving simulator. All of the warnings worked reasonably well for severe curves (45 km/h), regardless of demands from a secondary (cell phone) task. For less demanding curves, only those warnings with a strong perceptual component (i.e., implicit cues) were effective in reducing drivers' curve speeds in the presence of the cell phone task. The design implications of these data appear straightforward; curve warnings that contain perceptual components or emphasise the physical features of the curve work best, particularly in cognitively demanding situations. The cell phone task added to driver workload and drivers became less responsive to primary task demands (i.e., speeds were elevated and reaction times were longer).

Adolescent↗

PubMed2003

Restricting intersection visibility to reduce approach speeds.

This paper reports the field test of a visual restriction treatment for a rural intersection with a high rate of injury crashes. A human factors analysis of the asymmetric pattern of crashes at the site suggested that most of the crashes were the result of anticipatory decision-making occasioned by visual characteristics of the eastbound approach to the intersection. The field test examined the effectiveness of a visual restriction treatment directed at eliminating drivers' anticipatory decision-making. The treatment consisted of a hessian screen erected along the eastbound approach to the intersection beginning 125 m prior to intersection and ending 25 m prior to intersection. Over 2 days of testing, approximately 300 drivers' reactions at the intersection were observed and their responses to a brief survey recorded. The test indicated a 23% reduction in the 80th percentile and mean approach speeds and elimination of all approach speeds over 57 km/h following introduction of the treatment. Survey results showed that the treatment was visually acceptable to the majority of drivers using the intersection and did not affect its perceived safety. Follow-on analyses compared speed data before the treatment, and 2, 21, and 37 weeks after installation of the treatment. These analyses showed that approach speeds remained low; 30% lower than pre-treatment speeds for both the 80th percentile and the average approach speeds. Of perhaps the greatest significance, no crash resulting in serious injury or death has occurred at the intersection since installation of the treatment to the present time.

Acceleration↗