It very much depends on your national and local by-laws.
Certainly in the UK it is rarely worth fighting unless you can produce very strong evidence in your favour. Especially if a fixed-penalty imposed by a Council (typically parking, emission-area or bus-lane infringement).
You may have more right on your side if the ticket is from a private parking company acting for a supermarket, motorway service-area or the like: they are ruthless, bullying and often only just within the law. Commonly these companies will use pseudo-legal language and threats of debt-collectors (bailiffs) if you stand up to them, even though they know they have no legal right to do so unless first authorised by a County Court judgement in their favour - something that is not automatic.
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Watch for City Council tricks too, such as in Bristol.
Bristol city centre has Bus Lanes - so we all know we avoid driving in them. Only, it calls some, Bus Gates... pardon? By the time you've realised that's also a bus lane, not a junction-priority marking as I'd guessed wrongly, your car has been photographed. The traffic conditions at the time, including no buses running anyway, make no difference. The fine is £75 reduced to £35 for prompt payment - but if you appeal they will then charge the full balance, right or wrong, for your impudence!
Friends living near Bristol also tell me of motorists fined for entering a bus lane to allow an emergency-services vehicle to pass, and even of at least one main road where you are almost always forced into the bus lane anyway.
The city also has a low-emission area but like most of Bristol's inordinately tangled road network anyway, it is poorly sign-posted. Luckily the UK Government web-site has a section linked to the DVLA* records, so you can ascertain if your motor-vehicle (including a motorcycle) is compliant or not for any city with such a scheme.
If it's Glasgow, your vehicle won't be let in on payment of an emission-area charge, as in London, Bristol, etc. It won't be let in full-stop!
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*Driver & Vehicle Licensing Authority.
