A speed limit of 55 mph (88 km/h) is typically used on rural highways in the U.S. For locations where curbs are installed along these roadways, some transportation agencies have suggested the use of a reduced 45 mph (72 km/h) speed limit because, according to AASHTO, running into curbs at high speeds may cause significant vehicular damage and even severe injuries. However, it has also been argued that lowering the speed limit after the installation of curbs may cause confusion in drivers, who do not perceive the risk associated with the newly installed curbs and tend to operate their vehicles at the same, higher, speed as before. To better understand driver behavior on rural highways before and after curb installation and with different speed limits, researchers at the University of Tennessee conducted a series of experiments in two-lane and four-lane highways respectively on a high fidelity driving simulator. This paper presents the findings of the four-lane study and compares these to the results from the previous two-lane study. The scenario matrix consists of several dimensions including posted speed limit (45 and 55 mph, or 72 and 88 km/h), curb installation, lateral clearance between the edge of travel lane and the curb (2ft, 6 ft, and no- curb, or 0.6 m, 1.8 m, and no-curb), weather (clear and fog), traffic conditions in the next lane (1400 veh/hr and 400 veh/hr), etc. For each subject under different experimental scenarios, detailed driving parameters, such as driving speed and vehicle position in the travel lane, were recorded and analyzed subsequently. Results of the study suggest that driver behaviors are influenced by the various factors in a complex and interrelated manner. It is likely that drivers do not perceive the risk from the curb in determining their speed on four-lane rural highways. However, it is found that curbs may provide certain guidance to drivers, especially in selecting lane position. Comparing to the previous research in two-lane conditions, it is found that drivers are more likely to choose driving speeds according to posted speed limits, rather than roadway configurations. It is also found that the relative speed between driver’s vehicle and ambient traffic or curbs is an important factor determining drivers’ perception of risk and thus their driving behavior. The influence of subjective effects of these factors to their driving behavior is also observed in the study.
The speed limit of 55 mph (88 km/h) is typically used on rural highways in the U.S. For locations where curbs are installed along these roadways, some transportation agencies have suggested the use of a lower 45 mph (72 km/h) speed limit because, according to AASHTO, running into curbs at high speeds may cause significant vehicular damage and even severe injuries. However, it has also been argued that lowering the speed limit after the installation of curbs may cause confusion in drivers, who do not perceive the risk associated with the newly installed curbs and tend to operate their vehicles at the same speed as before. To better understand driver behavior on two-lane rural highways before and after curb installation and with different speed limits, researchers at the University of Tennessee conducted a series of experiments on a high-fidelity driving simulator. The scenario matrix consists of several dimensions including posted speed limit (45 and 55 mph, or 72 and 88 km/h), curb installation, lateral clearance between the edge of travel lane and the curb (2ft, 6 ft, and no-curb, or 0.6 m, 1.8 m, and no-curb), weather (clear and fog), visibility (day and night) conditions, traffic conditions in opposing lane (1400 veh/hr and 400 veh/hr), etc. For each subject under different experimental scenarios, detailed driving parameters, such as driving speed and vehicle position in the travel lane, were recorded and analyzed subsequently. Results of the study suggest that driver behaviors are influenced by the various factors in a complex and interrelated manner. It is likely that drivers do not perceive the risk from the curb or actually perceive more risk from the opposing traffic in determining their speed or lane position. In addition, the available space between the curb and the opposing traffic is crucial and has significant impact on driving behaviors.
Results are presented of various studies related to extended oil drain intervals in diesel truck engines. In a field test program, performance comparisons were made on two drain intervals in three different engines using both mono- and multi-grade oils. Three typical customer operations were monitored. Laboratory evaluations were made of typical and severely stressed used oils, and oil filter life and durability were assessed. It was concluded that proper engine installation and maintenance are the most significant factors in extending drain intervals and ensuring normal engine life. Efficient combustion and well-filtered air are essential in extending drain intervals. Abrasives are the major problem in such extension. High Total Acid Number (TAN) correlated with wear. Further investigation is needed to determine the TAN, Total Base Number (TBN) and wear relationship. Some of today's commercial oil filters have limited service life due to poor construction. The economics suggest that drain intervals of 30,000 to 40,000 km. provide the best cost/risk relationship for the Canadian environment.
Driving may be an important factor in self-care, autonomy and self-efficacy in elderly individuals. Thus, it is essential to determine what degree of impairment compromises safety for the preservation of autonomy. The objectives of this project were to determine the most reliable neurocognitive model to predict impaired driving ability in patients with early Alzheimer's disease (AD), and to determine specific interventions that may preserve safe driving in patients with early AD. We collected data from 60 participants in three groups: 20 undergraduate students (18–25), 20 normal elderly volunteers (55–90); and 20 patients with early AD. All participants completed a battery of neurocognitive measures. The participants then completed two driving tasks in a driving simulator (DriveSafety DS-600c) along with a 10-item screening adapted from actual driving test questions. The study monitored 10 driving parameters: adherence to stop signs and signals, sign recognition, following distance, pedestrian crossing, animal crossing, merging, gap acceptance, average speed, percent time exceeding posted speed limit, collisions, and ability to memorize new routes. AD patients performed less well than other groups on all neurocognitive measures. While AD patients maintained a larger average following distance and were compliant with signals, signs, and gap junctions with fewer collisions than other participants, they drove at a significantly lower average speed than other groups. Executive functions show the highest correlations with driving parameters. Data collection is ongoing and perceptible differences between groups and correlative strengths between neurocognitive domains are indicated. Driving is a process that relies heavily on all neurocognitive domains with a special emphasis on executive functions. This study found that one of the most important factors affecting driving safety in early AD patients is significantly reduced average speed, increasing the risk for accidents in urban areas. Another pressing issue for drivers with early AD is a reduction in the ability to learn new routes due to memory impairment. Significant deficits in numerous cognitive domains, visual-spatial deficits, or lack of awareness may indicate a need to cease driving.
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