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judgment, expectancy, information processing, and sensing), which may differ by age, gender, and experience. These lead to rules (e.g., drivers should be confronted only with one simple decision at one time). Human factors should influence design geometry, alignment, signs, signals, etc. Personal characteristics like eye height, vision range, etc., need to be identified. Generally, we design for the 85th percentile, to ensure both safety and economic performance.
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Vehicle
Vehicles operate in road environments and their characteristics need to be considered to ensure that they can safely operate. Vehicle dimensions such as length, width, and weight need to be identified and considered for safe road design and management. Performance of vehicles, such as acceleration, cornering, and braking, also needs to be considered.
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1. The Traffic System
The traffic system comprises three major components: humans, vehicles, and roads (Figure 1). Both human (drivers or controllers) and vehicle (moving parts) characteristics are essential elements for road design and management. The properties of both elements should heavily influence the design and safety of roads.
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Road crashes occur when a number of adverse factors combine to cause a failure of the traffic system. Although the dominant f actor in road crash causation is often the driver, the road environment often significantly contributes to likelihood and severity of road crashes.
The road element is the primary concern of the traffic engineer, but familiarity with the other components is essential. All three elements must be fully compatible for the system to operate without failure.
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Road
The road environment is the main concern of transport engineers. Road design and operational management are important areas that have a large influence on road safety (Underwood 2006; Ruediger and Mailaender 1999; Ogden 1996). Although driver and vehicle factors are often identified as the cause of crashes, a significant proportion of road crashes is attributable to the road environment.
Unit Nineteen
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Road Safety
Although the road system offers a high degree of mobility in Asian cities, a large amount of personal trauma is experienced through crashes. The term “crash” is preferred to “accident” since accident implies accidental and these events are unavoidable and nonpreventable. Crashes are considered a failure of the system that can be eliminated through good engineering.Leabharlann TextHuman
Humans control the vehicle, taken as given (static), but there must be detailed knowledge of the characteristics (e.g., vision, memory, reaction time,