Despite the doubts, and despite complaints from shop owners, London’s congestion charge --introduced in February 2003 -- has managed to ease the gridlock in the city centre. Traffic is down by 18%, jams by 30%. The scheme’s biggest weakness is that it is crude: drivers pay ￡ 8 ($14) to enter the zone between 7am and 6:30pm, regardless of how congested the roads are, or how long they stay.
So road-pricing fans are watching trials by Transport for London (TfL) of a new detection system, called tag-and-beacon, with interest. Under such a scheme (used in Singapore and on some European roads) cars are fitted with electronic tags that are read by roadside masts. If the trial is successful, TfL says that the city could switch to the system once the contract to run the congestion charge is re-let in 2009.
Currently, cameras are used to read license plates and track motorists. They are not always reliable: an individual camera identifies only around 70% of cars
A. has got much support from shop owners.
B. has reduced 18% of traffic jams.
C. asks $14 for entering the city center after 7pm.
D. demands same charges from drivers in spite of road conditions.
Despite increased airport security since September 11th, 2001, the technology to scan both passengers and baggage for weapons and bombs remains largely unchanged. Travellers walk through metal detectors and carry-on bags pass through x-ray machines that superimpose colour-coded highlights, but do little else. Checked-in luggage is screened by "computed tomography", which peers inside a suitcase rather like a CAT scan of a brain. These systems can alert an operator to something suspicious, but they cannot tell what it is.
More sophisticated screening technologies are emerging, albeit slowly. There are three main approaches: enhanced x-rays to spot hidden objects, sensor technology to sniff dangerous chemicals, and radio frequencies that can identify liquids and solids.
A number of manufacturers are using "reflective" or "backscatter" x-rays that can be calibrated to see objects through clothing. They can spot things that a metal
A. Their efficiency.
B. Their brand.
C. Their output.
D. Their component.
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