With Manchester being given the all clear to proceed with plans for a congestion charge, it brings in to the open that only one other city has expressed a clear and definite interest in joining London in having a congestion charge.
There is, the aspect of political self interest. Any council, and party, likely to introduce a congestion charge will see the fate that befell Ken Livingstone and will no doubt take heed. This is going to be the biggest disincentive of all. But there are more important issues.
Manchester has more than one public transport network, with the city being bless with the Metrolink light railway "tram" system, in addition to buses. This means Manchester commuters have more choices and Manchester itself has more avenues through which to channel the cash they will receive from motorists. But what of other cities ?
Cambridge has applied to the government to introduce a charge. However apart from buses and their park and ride system, there are few alternatives. The same could be said of virtually every other town and city in the UK except for a handful.
So in truth, even if you are a fan of congestion charging, in reality it is a non starter for most of the country and always will be.