大学六级-421及答案解析.doc
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1、大学六级-421 及答案解析(总分:703.00,做题时间:90 分钟)一、BPart Writing(总题数:1,分数:106.00)_二、BPart Reading (总题数:1,分数:70.00)B Intelligent Transport System/BToday, there are many ways to travel around a large metropolitan area, for work or pleasure. You could walk, although the range is admittedly low. You could bicycle, b
2、ut you still do a lot of work, and its dangerous. You could drive a car, which takes concentration and sobriety and a license. You could ride a bus, and let someone else drive. You could take a train, and let a computer drive you. Or you could fly, and wait a long time for the plane to take off and
3、land.All modes of transportation have advantages, and disadvantages. However, in recent decades, the single system that has won over all others is the private automobile. This allows you to go from your starting point to your destination point, with your complete control, at a reasonable speed in a
4、reasonable time. Unfortunately, apart from the pollutants created by the vehicle itself, the fact that so many other people seem to enjoy its perceived freedom causes major traffic jams, and the requirement for traffic control devices.Too many people using too little road space at the same time caus
5、es traffic jams. It is most profound on large grade separated roads, that have limited access. There have been various solutions tried out, including high occupancy vehicle lanes, ramp metering, or road widening. Unfortunately, they simply dont solve the problem of lack of capacity.Traffic control d
6、evices impose certain controls on the flow of traffic. Most common are traffic lights. These meter the flow of traffic between two or more roads so that at no time is any vehicle in conflict with any other. However, they also impose that traffic comes to a complete stop, requiring vehicles to stop a
7、nd then start again. This not only slows vehicles down, but also is the prime cause of wasted energy in urban settings.Unfortunately, cities are very reluctant to spend money. Therefore any future transport system has to be cheap for cities. This implies that current infrastructure is kept as much a
8、s possible, or improved. Using roads, the prime infrastructure available today would mean the form factor for vehicles would stay the same, but each individual vehicle could be made more intelligent.So for tomorrow, we need to design a transport system that uses roads or a very slight improvement on
9、 roads to provide a high capacity system that provides service for everyone. This could be achieved by implementing the following eight systems, each of which provides more of a burden on the car manufacturer, but would eventually provide a system, which is automatic, safe and efficient.Firstly, all
10、 cars should have intelligence brakes and cruise control. These would remove the driver from the responsibility of having to follow along behind somebody. By pressing a button, the driver would give control of the distance between his car and the car in front. If the car in front slowed down, you wo
11、uld not have to wait for the brake lights to light up, the driver to see them, Wen press the brake pedal the right amount, and continuously monitor the distance. Instead the car would be programmed to continuously monitor the distance to the car in front and instantly alter its speed to match and ma
12、intain the distance.By speeding up the feedback circuit, you can close the distance of cars, and therefore increase the capacity. You also remove driver error so reducing the number of accidents. Also, cars could communicate locally with each other and ware ahead of time that following cars need to
13、slow down.Next, you need to remove the driver from the responsibility of steering the vehicle. Having complex vision systems on a car seems over the top as they not only dramatically increase the cost of the car, but also the complexity of the control software. Instead you could build detector into
14、the front of the car that detect the middle of a lane of traffic. The car would try and keep the vehicle in that lane. Junctions could be built by having the centerline split. The operator or route planning software would decide which of the two or more signals to follow.Separating lanes of automati
15、c cars from those driven by humans especially on high speed highways, would give an incentive to not only purchase an automatic car but also to purchase the road space which it uses. Since these separate lanes would have not only fast moving traffic but also safer traffic, they could be marked and s
16、old by cities to create a revenue stream to allow the building of more augmented roads.Having a device in the car that does route planning is a great help for people who dont know the way around your city. But what if you lived in the city for many years? Its not going to be that much use, is it? By
17、 linking route planning with real time information on traffic levels in the city, you can quickly divert your journey to use the most efficient roads. This information could be relayed to vehicles using broadcast radio. Roadside sensors that determine the flow of traffic on a road would detect the s
18、peeds.The ability to remove the parking requirements from near a building would allow more compact cities, which are better pedestrian environments. However, people dont like to walk from a parking structure that is a long way from their destination. The solution is to allow the car to drop off the
19、passengers where required and then drive itself to the nearest parking structure that is known to have a space.By automatically controlling the speed and location of all traffic, you can make junctions work very efficiently. At the moment, some traffic has to stop, and when it resumes, the cars spre
20、ad out into a large disperse volume. Instead you could move each group of cars as a packet, adjusting its speed so that it arrives at an intersection at just the right time so that it never has to stop. This could be achieved by changing the speed of a section of road so those cars slow down gradual
21、ly. The speeds of road segments would be set by nearby junction computers each linked to the other. This would create a holistic traffic control system. If one section lost power, the system would revert to a normal junction.When a group of people move from one location to another, it would make sen
22、se to allow them to travel together instead of having to each use a separate vehicle. On demand group transport would allow the request of a large vehicle which can automatically move people from one location to another. These vehicles would be stored at strategic locations, and then sent to the req
23、uesting site as quickly as possible. Vehicles could be booked in advance, and you pay by the time used in minutes, not the distance traveled or destination.At the other end is the replacement of the taxi. This would be similar to the group transport but for smaller groups. Again these vehicles would
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