My dad said he was driving on a road miles away from the nearest town. he said he saw a glowing green ball fly by the side of the car.When he noticed it was following his car, he tried to get rid of it. He turned, went over hills, and it went right in front of him. As he went up another hill, it curved up and dissapeared over the horizon.

perfect desciption of what happens with what i call roadside abductions, did he have any missing time associated with it, even a few minutes is enough 

he said he didn't remember any time being lost.

He said he was driving so he couldn't check his watch.

hmm,  i will stick by what i have said above,  was it at night, although that doesnt sometimes matter as it happened to my mum mid afternoon on a packed road and area,  they can abduct you without you knowing anything as they erase your mind anyway has he had any other wierd experiences or any of the family? 

my grandma pratt saw a huge bright light behind her. their was no car.

hmm again, if it was i am saying these things occur in families[ occasionally it is one person from the whole family] and if you dig around i would think these are not isolated incidents, where was you're nan when she saw the bright light?

I don't know.sorry.