"Bus Driver" joke

John was on his way to work. He got on his bus and sat down. After a while there is a small bump.
John; "What was that?"
Driver; "It was a cat"
John; "Why did you run it over?"
Driver; "Well it was either that or swerve into the tree at the side of the road and kill us all!"
John; "Oh, fair enough"
A little farthur down the road the bus swerves suddenly and a bigger bump shakes the bus.
John; "What was that!!?"
Driver; "It was a dog"
John; "Why did you run it over?"
Driver "I couldn't help it, I tried to swerve but I hit it by accident"
John; "That's awful but I suppose you did try to swerve"
The bus continued on its journey but later on it swerved again and there was a small bump followed by a large thud.
John; "What is it this time?"
Driver; "I hit an old lady"
John; "Oh my god. Is she alright?
Driver; "No she's lying in a pool of blood by the side of the road."
John; "I can't believe this! Why did this have to happen on my journey."
The driver called for an ambulence and the bus set off again. When John got off the bus, he asked the driver: "If the big bump was the old lady, what was the small one?"
The driver simply replied "I had to go on the pavement to get her!"