Am i doing something wrong?

Cassie came to us never properly lead trained and we have worked hard to get her walking to heel by keeping her guessing which way we are going like changing direction, just stopping and waiting till she comes back to heel. But Cassie now seems to have developed a habit/fear i don't know which since i had been away, but now i walk her all the time again she has started to become obsessed with cars, i can't tell if she skips forward because she is scared of the cars or running to try to chase them. It is becoming a real issue as i have stood on her paw a few times and i nearly fell over her just now and it could be dangerous for the both of us. When there are few cars like the 5am walks are not an issue as she walks superbly well. I have tried distracting her with treats,running when cars are coming,talking to her lots and making her sit and watch them while i stroke her, i may look stupid but it's safer for us both if we just sit and watch the traffic. It is getting rediculous now with the lead training and now sitting and waiting for cars and I don't know how to change it can anybody advise me please

The skipping forward is almost certainly fear. Do you know if anything happened while you were away?

Next time you're out, keep an eye on her & try to watch her body language when she does it - ear position, body shape, tail position etc.

Thanks Caryll, i never even thought of asking if something had happened i would hope they would tell me since i have mentioned the problem a few times. Sometimes she does cower ears/tail down and she tries to bend herself around my legs to see. I did actually think it could be sound based because tractors and 4x4 seem to have a whining noise and she seems worse. Is that a silly notion? I am pleased we only have a short road walk but i am at a loss as to how to make the walk better for Cassie

Take some treats with you next walk. Is she's spooked just stand still & call her back to you in a normal voice & treat her when she comes back. It may take a while, but hopefully it'll start to lessen.