Objective: The few observational studies of the prevalence of high beam use indicate the rate of high beam use is about 25% when vehicles are isolated from other vehicles on unlit roads. Recent studies were limited to 2-lane rural roads and used measurement methods that likely overestimated use. The current study examined factors associated with the rate of high beam use of isolated vehicles on a variety of roadways in the Ann Arbor, Michigan area.
Methods: Twenty observation sites were categorized as urban, rural, or on a rural/urban boundary and selected to estimate the effects of street lighting, road curvature, and direction of travel relative to the city on high beam use. Sites were selected in pairs so that a majority of traffic passing one site also passed through the other. Measurement of high beams relied on video data recorded for 2 nights at each site, and the video data also were used to derive a precise measure of the proximity of other traffic. Nearly 3,200 isolated vehicles (10 s or longer from other vehicles) were observed, representing 1,500-plus vehicle pairs.
Results: Across the sample, 18% of the vehicles used high beams. Seventy-three percent of the 1,500-plus vehicle pairs used low beams at each paired site, whereas 9% used high beams at both sites. Vehicles at rural sites and sites at the boundaries of Ann Arbor were more likely to use high beams than vehicles at urban sites, but use in rural areas compared with rural/urban boundary areas did not vary significantly. Rates at all sites were much lower than expected, ranging from 0.9 to 52.9%. High beam use generally increased with greater time between subject vehicles and leading vehicles and vehicles in the opposing lane. There were mixed findings associated with street lighting, road curvature, and direction of travel relative to the city.
Conclusion: Maximizing visibility available to drivers from headlights includes addressing the substantial underuse of high beam headlamps. Advanced technologies such as high beam assist, which switches automatically between high and low beam headlamps depending on the presence of other traffic, can help to address this problem. 相似文献
ABSTRACT: Six years (1989–1994) of data from New Zealand's National Rivers Water Quality Network were used to characterize the optical water quality regime of river waters as regards: visual clarity (black disc visibility), turbidity, and light-absorbing aquatic humic material (referred to as ‘yellow substance,’ measured as light absorption at 440 nm). Quantitative relationships between optical water quality variables and flow in rivers are well-described by power law expressions. Visual clarity usually decreases strongly with increasing flow in individual rivers. There is a strong, inverse relationship between turbidity and visibility, but, because of differences between sites, turbidity is not a good general predictor of visual clarity (the attribute of real interest) in rivers. Yellow substance tends to increase with increasing flow, probably because during rainstorms, soil water high in yellow-colored humic material, rather than rain water or ground water, dominates discharge. Therefore, rivers are typically clear and low in humic matter at low flow, and turbid and yellow-colored at high flow. 相似文献
Several approaches can be used to define and construct visual buffer strips around proposed new facility sites in a forested
environment. A visual buffer strip of a given value, defines a region around an object within which the probability of an
unblocked view of all or portions of it by an observer are less than the buffer strip probability value. Two primary approaches
are used to define visual buffer strips that take into account the size of the vegetative elements and their individual effects
on visibility. Several variations and combinations of the approaches are possible. One approach defines a visual buffer strip
based on the average probability of a clear view of points along the object by an observer; the other approach is based on
the visibility of the feature as a whole. The computation and construction of visual buffer strips based on these two concepts
are presented. Comparisons of the two approaches for specific feature shapes are also described. 相似文献