Free Traffic Legal Advice

I arrived at the UK last year, and bought a car last month. I use my car to take my children to their school. There is one street that I was not sure that I can go through it, but I saw 3 cars passing the street, so I thought the street is open to public vehicle. After a month using that street, comes penalty charge notices stating that I was being in a bus lane. So I know it's my fault and maybe the other cars were local residents and they have the right to go through that street. My question is, is it possible to reduce the charge? Because one charge is £70, and I have been passing that street for like 30 times 😭

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