Search Results

This report provides updated information regarding the market-weighted prevalence of various headlamp design attributes in the U.S. and a summary of recent trends for these design attributes. The main findings were as follows: (1) there was a general transition from dual-filament light sources in 1997 to single-filament sources in 2007; (2) the preferred optics changed from lens-based in 1997 to mostly reflector-based optics in 2007; and (3) while mechanical aim was the most frequently specified aiming method in 1997, the 2007 sample made nearly exclusive use of visual/optical aiming (with visual/optical right side as the most common specific type).

This study evaluated the relative effects of horizontal and vertical misaim of low-beam headlamps. The approach involved analyzing light-output matrices of 150 production low beams, manufactured for sale in the U.S., Europe, and Japan. The specific analysis involved computing, for 225 locations in the central part of each beam pattern, the ratios of nominal intensity and intensity for vertical and horizontal misaim of up to 1.5°. The ratios greater than 1 log unit were considered to be of practical significance in terms of changes in visual performance and discomfort glare, and those greater than 0.5 log unit of likely significance. Only changes relative to visual performance and glare under nominal aim were considered; absolute levels were not examined. Furthermore, simultaneous horizontal and vertical misaims were not considered.

We collected photometric data, concerning the simultaneous levels of rearview mirror glare and luminance of the forward scene, in order to characterize the night driving environment for rearview mirrors. An instrumented vehicle was used to collect photometric data for each combination of three road types (urban, expressway, and rural) with two pavement conditions (dry and wet). We then used these data to quantify the benefits of variable-reflectance rearview mirrors relative to (1) fixed-reflectance mirrors, and (2) two-level prism mirrors. The performance of the various types of mirrors was quantified in terms of a figure of merit. The figure of merit is simply the percentage of the time that all of three mirror-performance measures are met: (1) discomfort glare, (2) forward visibility, and (3) rearward visibility.

This study evaluated the SAE J1735 Draft Proposal for a low-beam headlighting pattern in relation to the current standards in the U.S., Europe, and Japan. The approach consisted of the following steps: (1) identifying a set of 15 important visual performance functions (including seeing and glare) for low-beam headlamps; (2) defining the relevant geometry relative to the visual performance functions; (3) setting criterion values of illumination for each of the visual performance functions based on the available empirical data; and (4) evaluating the standards relative to the criterion values by using the worst-allowed-case approach (evaluating the minima specified by the standards for seeing functions, and the maxima for glare functions). The results indicate that the SAE J1735 Draft Proposal tended to require better performance than the current U.S., European, and Japanese standards.

The goal of this study was to provide information about the frequency of installation and use of fog lamps. Two surveys were performed. In the first one, installation of fog lamps was estimated by a survey of parked vehicles in two iarge shopping centers. The second survey studied the usage of fog lamps during daytime and nighttime, under clear, rainy, or foggy conditions. In this survey, an observer in a moving vehicle noted the types of lamps that were energized on the fronts of oncoming vehicles, and whether fog lamps were installed at all. The main findings are: (1) The best estimate of the current frequency of installation of fog lamps in southeast Michigan is about 13%. (2) During daytime, the usage of fog lamps increased with deterioration in atmospheric conditions, with the usage reaching 50% of all installed fog lamps during moderate-to-heavy fog.

A class of heavy truck vehicles, characterized primarily by high centers of gravity, was studied using analysis and computer simulation to identify and understand the relationship between directional and roll stability of such vehicles during steady turning maneuvers. Findings of the computer-based study suggest: (1) directional instability (yaw divergence) is possible for such vehicles during steady turning while operating at elevated speeds on horizontal road surfaces, (2) yaw divergence will lead to rollover in the absence of corrective steering action and/or reduced speed, and (3) the primary mechanism responsible for precipitating yaw divergent behavior in such vehicles is the nonlinear sensitivity of truck tire cornering stiffness to vertical load acting in combination with typical heavy truck fore/aft roll stiffness distributions. In addition, the influences of roadway superelevation and driver steering control as contributors to vehicle stabilization are examined and discussed.

This paper presents examples of passenger car crashes with 3-point restrained front seat occupants. Detailed case capsule descriptions that include car make and model, injury descriptions and severity, and contacts producing the injuries.

A nationwide survey was conducted of the condition of vehicle lighting equipment. Twenty different sites were visited and a total of nearly 1, 000 vehicles included in the sample. Headlamp aim and dirt levels were measured and the condition of marker and signal lamps noted. The results of the survey indicate that many vehicles have headlamps that are badly aimed. The condition of front and rear marker and signal lamps is generally good, with more than 98% of such units functioning. Side marker lights were in poorer shape, hut more than 90% of these were operating. Consistent differences were found between areas with and without vehicle inspection programs. It appears that such programs are effective in improving the condition of vehicle lighting systems.

Suggestions for pictographic symbols for identifying automotive controls and displays were obtained from 32 drivers. A total of 142 symbol candidates were developed from these suggestions for 25 functions. Subsequently, 104 people at a driver licensing office ranked these candidates and corresponding symbols in ISO Standard 2575 from best to worst. The criterion was how well the candidates represented the functions of interest. Based on those data the authors recommend replacing the ISO symbols for the lighter, fog lights, hood release, master lighting switch, and temperature and continuing to seek alternatives for the front defrost, hazard, headlamp cleaner, high beam headlamps, unleaded fuel, parking lights, rear defrost, windshield washer, and windshield washer/wiper.

Physical prototypes of two forms of intelligent subsystems for increasing a truck driver’s ability to maintain stable operations with an articulated heavy-duty vehicle have been designed, constructed, and demonstrated. The two systems deal, respectively, with (1) quasi-steady-state rollover and (2) rearward amplification of lateral acceleration (especially in multi-articulated trailer combinations). Both forms of instability have been documented through prior research and both are known to influence the crash record. Results from testing show that both systems are viable from a technical point of view.

Many traffic accident cases involve questions of driver visual perception. It is common for one or both sides to employ experts in such matters. These individuals often make use of reconstructions in an effort to arrive at an opinion concerning driver perception. While such reconstructions can be helpful, they can also be very misleading. The purpose of this report is to review basic information concerning visual perception, to lay a foundation for understanding how the visual system works under nighttime driving conditions. Applied research on night driving will be covered as well, with a particular focus on detecting conditions in the forward field. The report concludes with a section on problems that can degrade visual performance at night.