The Climate Action website (associated with the UN Environment Programme) has published an article by Alan Bouquet reviewing congestion charging. Given the website's primary interest is reducing CO2 emissions, it understandably take a fairly limited view of congestion pricing as a tool, but I am glad that it is promoting it as a positive. Given congestion pricing simply reduces traffic flows on congested routes by pricing some vehicles off the road, it is understandably popular with those seeking to reduce use of cars.
The article states the obvious ways of introducing congestion charging as:
• A cordon area around a city center, with charges for passing the cordon line
• Area wide congestion pricing, which charges for being inside an area
• A city center toll ring, with toll collection surrounding the city
• Corridor or single facility congestion pricing, where access to a lane or a facility is priced.
• Area wide congestion pricing, which charges for being inside an area
• A city center toll ring, with toll collection surrounding the city
• Corridor or single facility congestion pricing, where access to a lane or a facility is priced.
The cordon and toll ring examples aren't exactly different, and it ignores multi-zonal or distance based pricing - the option with the best potential to target roads with optimal pricing.
The negatives it cites are that it is "not equitable" (but doesn't explain why), that it "puts a burden on neighbouring communities" (only if it is a blunt badly designed cordon), that it "affects retail businesses and the economy and is another form of tax" (which can be true if badly designed and if the revenue collected is not wisely used).
The article claims there are "many unanswered questions". These are worth testing:
"Significant investment in public transport is required to offset the loss of commuters using cars. For the system to work, viable alternatives must be in place"
I disagree. For a start not everyone priced off the roads at peak times are commuters, but people who can travel at other times. Secondly, it can price people onto other routes and to other destinations. Estimates in London are that a third of motorists changed time of travel or route (some simply avoided driving through the centre), a third changed mode and a third didn't travel at all (combining multiple trips into one trip). Public transport needs to be able to operate more efficiently and meet increases in demand, but often it is also underpriced as well. Congestion pricing raises the bigger issue as to addressing the fundamental pricing problems in urban transport.
"The funds raised from the charge are not always put back into improving transport, which is a major criticism of the scheme."
Given there are only three major schemes (Singapore, London and Stockholm), this criticism is only valid in Singapore, but isn't a big issue there. The funds could be used to offset other motoring taxes quite legitimately. It does help for money raised to be used to improve transport or reduce other taxes, rather than simply be a windfall.
"The process of charging raises inequality questions. Middle class and high earners are more likely to be able to afford the charge, possibly raising unemployment among the lower classes."
This is why part of revenue raised should be used to offset cutting other taxes, which can address this. However, any charge which raises unemployment is poorly designed indeed.
"Referendums on whether to implement charging or not, like in Stockholm, show that those outside the city are against the charge, while those in the city are for it."(sic)
There have been three referenda on congestion charging. Stockholm's result was as described, but in Edinburgh and Manchester the vote was overwhelmingly negative, with majorities against across the board. That statement has little validity.
The article concludes that congestion charging can work "it also enables a cleaner flowing city, if implemented with masses of investment in alternative methods of transport."
However, that is a narrow way of looking at congestion pricing. It is only partially about promoting mode shift, but also significantly about time and route shift. Congestion pricing can enhance the viability of existing services, and can justify improvements, but it requires a deeper investigation of impacts than simply assuming mode shift.