I. VEHICLE AND HUMAN FACTORS
Three major components affect driving: the vehicle, the roadway/environment, and the driver. In this chapter, vehicle and driver characteristics and how they are affected by the environment and physical properties of the roadway are identified. The characteristics and performance of motor vehicles play a major role in defining the fundamentals of traffic flow and capacity. Human behavior also contributes to the characteristics of traffic flow on a facility.
MOTOR VEHICLE CHARACTERISTICS
This ction summarizes the operating characteristics of motor vehicles that should be considered in analyzing a facility. The major considerations are vehicle types and dimensions, turning radii and offtracking, resistance to motion, power requirements, acceleration performance, and deceleration performance. Motor vehicles include pasnger cars, trucks, vans, bus, recreational vehicles, and motorcycles. The vehicles have unique weight, length, size, and operational characteristics. The forces that
must be overcome by motor vehicles if they are to move are rolling, air, grade, curve, and inertial resistance. The weight/power ratios are uful for indicating the overall performance in overcoming the forces. Exhibit 8-1 summarizes typical motor vehicle weight and power for different vehicle types.
Vehicle acceleration and deceleration rates are factors in designing traffic signal
timing, computing fuel economy and travel time values, and estimating how normal
traffic flow is resumed after a breakdown. Vehicle acceleration rates of pasnger cars ac开学典礼主题标语
celerating after a stop range between 3 and 13 ft/s2, while pasnger car deceleration
rates range between 7 and 26 ft/s2 (1).
DRIVER CHARACTERISTICS
Driving is a complex task involving a variety of skills. The most important of the skills involve taking in and processing information and making quick decisions bad on this information. Driver tasks are categorized into three main elements: control,guidance, and navigation. Control involv张智霖的老婆
es the driver’s interaction with the vehicle in terms of speed and direction (accelerating, braking, and steering). Guidance refers to maintaining a safe path and keeping the vehicle in the proper lane. Navigation means planning and executing a trip.
The perception and processing of information are important driver characteristics. About 90 percent of the information a driver receives is visual. A significant component in the successful processing and u of information is the speed with which this processing is done. One of the parameters that is ud to quantify the speed of processing information is perception-reaction time, which reprents how quickly a driver can respond to an eme
rgency situation. The parameter called sight distance is directly associated with reaction time. There are three types of sight distance: stopping, passing,and decision. This parameter is ud to d哪一个的英文
etermine geometric features of transportation facilities.
Other factors like nighttime driving, fatigue, driving under the influence of alcohol and drugs, elderly drivers, and police enforcement contribute to driver behavior on a transportation facility. All the factors can affect the operational parameters of speed,delay, and density.
PEDESTRIAN CHARACTERISTICS
Pedestrian speed is probably the most important characteristic of a pedestrian facility that is affected by individual pedestrian behavior and habit. Among veral factors that influence walking speed are density, gender, size of platoon, percentage of elderly population, handicapped pedestrian population, and child pedestrian population. An average walking speed of 40-ft/s is appropriate for typical groups of pedestrians. The amount of space required by a queued or standing pedestrian is 8.0 ft2. At signalized int
erctions pedestrian crossings must be assigned an amount of effective green time bad on average walking speed.
BICYCLE CHARACTERISTICS
The bicycle and the bicyclist have very different characteristics and exhibit different operation than do drivers of motor vehicles. The typical speed of bicycles is about 15 mi/h. Among other factors that affect bicycles are the type of bicycle, the bike path surface type, weather conditions, the grade of the path, and the mix of other nonmotorized urs on the bike path.
BUS AND LIGHT RAIL CHARACTERISTICS
Bus and light rail capacity are affected by vehicle type, loading area performance, and dwell time of the bus or light rail vehicle. Each bus requires a certain amount of rvice time at stops that varies with the number of boarding and alighting pasngers,
door configuration, and fare collection method. The minimum safe spacing between
bus in motion and the number of loading areas available at any stop also influence the total number of bus and persons that a given facility can carry. The total pasnger flow rate varies with bus capacity and the trade-off between ated capacity and standees. The largest number of ats and lowest number of standees should occur on longer suburban bus routes or on intercity bus routes where higher levels of comfort are esntial. A typical 40-ft urban transit bus can normally at 43 pasngers and carry up to 37 standees if the aisle circulation space is filled. Similarly, a 60-ft articulated bus can carry 65 ated pasngers and 55 standees. However, bus operator policy often limits the number of standees to levels below this theoretical capacity.
