Roy Trenton used to drive a taxi. A short while ago, however, he became a bus driver and he has not regretted it. He is finding his new work far more exciting. When he was driving along Catford Street recently, he saw two thieves rush out of a shop and run towards a waiting car. One of them was carrying a bag full of money. Roy acted quickly and drove the bus straight at the thieves. The one with the money got such a fright that he dropped the bag. As the thieves were trying to get away in their car, Roy drove his bus into the back of it. While the battered car was moving away, Roy stopped his bus and telephoned the police. The thieves' car was badly damaged and easy to recognize. Shortly afterwards, the police stopped the car and both men were arrested.

# Read and answer this question: How did Roy stop the thieves?