A、By giving alarming when the drivers drink. B、By measuring alcohol levels manually. C、By making the drivers unable to use their

It is remarkable how risk-conscious people have become, especially on the road. Sure, some motoring maniacs (疯子) will always push their luck, causing harm for themselves and others, and everyone makes mistakes from time to time, gets distracted, becomes impatient and is, perhaps, not as mindful of other road users as he ought to be. Nevertheless, (26)the statistics for traffic accidents, at least in developed parts of the world, reveal an encouraging downward trend. In the United States, for instance, the latest figures from the National Highway Traffic Safety Administration (NHTSA) show that 33 808 people died on American roads in 2009, the lowest level since 1950. For that, (27) traffic authorities everywhere can thank the wholesale introduction of safety belts and airbags, as well as tougher drunk-driving laws. As could be expected, the recession has played its part in reducing the deathly toll on the road, especially among the most vulnerable group, 16- to 24-year-olds. They have suffered most from unemployment and hence have been exposed to less harm on the road. (28)The NHTSA worries that there could be a rebound in accidents once the recovery gets seriously underway and the young resume their careless driving habits. But the technologies NHTSA is putting greatest emphasis on are those that keep drunk motorists off the road. Across America, a third of traffic accidents these days are related to the use of alcohol. One system uses sensors developed by QinetiQ North America that can measure a person’s blood-alcohol content through the skin. (29)Attached to the steering wheel or the door handle, the device would stop anyone over the limit from driving home.
26. What can we learn from the statistics for traffic accidents?
27. What caused the decline of the number of people who died from traffic accidents?
28. What do the officials of NHTSA worry about?
29. How does the sensor work to keep drunk drivers off the road?