CIn January 2004, a 20-year-old woman ran a red light while talking on a cell phone. Her car knocked into another car crossing with the green light directly in front of her. The police found the driver never touched her brakes（刹车）and was traveling 48 mph when she hit the other car. The police were told that the driver was not looking down, pressing buttons. She was looking straight out of the windshield（挡风玻璃）talking on her cell phone as she passed four cars and a school bus.Vision is the most important sense for safe driving. Yet, drivers using cell phones are likely to "look at" but not "see" objects. It is said that drivers using cell phones look but fail to see up to 50 percent of the information while driving. Drivers are looking out of the windshield, but they do not really deal with the situation on the road.Although the public appear to be turning against cell phone use while driving, many admit they regularly talk or text while driving. The police say that nine percent of the drivers at any given time are using cell phones, and about one in four car accidents are directly related to cell phone use.Using cell phones while driving has become a serious public health threat（威胁）. A few states have passed laws making it unlawful to use a handheld cell phone while driving, but these laws give the false message that using hand-free phone is safe.What do we know about the laws making it unlawful to use a handheld cell phone while driving?