cnn s alex anner hill is working the story for us. whenever i m on a freeway and i m passing a bus, i m wondering, who is looking after these things? now i hear about this crackdown. why now? what happened? how many people are getting shut down and for what reasons? that s a lot to throw at you. a lot of these people have been asking these questions. a federal agency oversees these passenger buses. this is a big industry we re talking about. the federal motor carrier safety administration says that there are 700 million passenger bus trips every year and there are 4,000 different bus companies. big industry to regulate. it gets most exhaustive crackdown, most in-depth investigation. they started by looking at 250 of the most at-risk passenger bus lines, the most at-risk companies based on their records. eight-month long investigation with 50 investigators as a result of the investigation.