Anyone else who tried to harness train their cat?

I tried to harness train my recent shelter adoption, she was born in a cage at the shelter. I had her a good month before I tried this--she was used to staying inside the house and never tried to go outside. Therefore, I thought it would be good to try her with the harness because I didn't want her freaking out about cars, or if she did, she wouldn't run out in front of them.

It was an epic fail. I tried so many times and she just really didn't take a liking too it. I had her on it one day as I was going to check the mail, (she tended to follow me to the mail box and play in our busy road) and this big diesel truck drove by and she ran up my back and onto my shoulder, but left horrible claw marks on the way up.

I know she didn't mean to hurt me but it was something she just wasn't ready for. The harness or the traffic. But after that day, she stayed out of the road.