Has the congestion charge been a success? Would you like to see any changes?

Norris: No. I would scrap it on day one. And I would cancel all outstanding fines. It's good public policy. You don't want to pay a lot to chase relatively small sums of money. Proving that you can reduce traffic is proving nothing. And the damage to business has been immense. The CBI, London First, have all been saying to Ken, Look this is really bad for business.'

Livingstone: The most this zone could expand would be to three times its size. It will take us up to 2006 to double its size. By then, we will be so close to the Government's national road pricing that we would want to wait for that. It's appropriate to a heavily congested centre. In the suburbs you have some roads that are congested and many others are relatively free. At the North Circular Road (NCR) it would be disproportionate a lot of people have to use their cars and can't afford to pay £5 a day.

Johnson: I think it has been a fantastic success. There are 50,000 fewer cars coming into London and most people have seen dramatic cuts in traffic. Congestion charging has always been a Green policy. We want to extend it and have one policy for the whole of London with three different zones: the centre, up to the NCR, and outer London, up to the M25. There would be a 90 per cent reduction for people travelling within their own area. So the £4 charge for outer London would only cost 40p for those travelling in their area. It would stop a lot of people who are driving through London. I also want to put a levy on company car parking and out of town shopping centres. The first few spaces would be free because we don't want to hurt small businesses.

Hughes: It is something I have always supported. There should be a buffer zone for people who live close to the zone and more exemption's for people such as social workers and postmen. I would make it more user-friendly. You would be able to pay in advance easily and if you forget to pay by before 10pm, you shouldn't get clobbered, you should get until the following day. To help visitors: no charge between Christmas and New Year because that is when the sales start and every car would have five free journeys before they start clocking up their charge. It is not the time to expand westward. The only place it could be extended in the foreseeable is any of the five boroughs where it already covers part of the borough and if the rest of the people in the borough wanted it.

Should we have tolls on the North Circular Road?

Johnson: In terms of charging, the congestion zones would be my man aim. With my plan, the NCR would be part of the congestion charge, but you wouldn't have tolls on top.

Norris: No, because it would act as a deterrent to people using the road. But we ought to get rid of the bottleneck between Staples Corner and the M11. The answer to orbital congestion is to improve public transport and encourage more cycling and walking, with possible Tube extensions.

Livingstone: I have no proposal for tolls on the NCR.

Hughes: In the immediate future that is not going to happen. The NCR does get congested, but it is the outer ring road for London and there is no orbital public transport, so it would be quite unfair to add further costs to people. I want to improve the rail services and bus services that go around the towns from the Harrows to the Barnets round to Wansteads.

And tolls for Heathrow?

Johnson: As with the NCR, Heathrow would be part of the Greens' congestion zone.

Norris: No, it's more about managing transport. I'm very much against a third Heathrow runway.

Livingstone: Not in Heathrow. We did some research and found it would actually be cheaper to do a deal with the British Airports Authority and increase parking charges at Heathrow.

Hughes: No tolls, and no charging in Heathrow. Everyone is looking at road tolls. In five or ten years we might allow for all cars to be linked to a GPS (global positioning system). In certain areas or times, such as rush hour, you will be charged.

What do you think of the west London Tram Link?

Livingstone: If we can't make it work on the Uxbridge Road it won't work anywhere. Of course there will be disruption. Everyone now thinks Trafalgar Square is a stunning new addition to London but it was hell doing it. If someone can find a way to create new things without causing disruption they should get the Nobel prize.

Hughes: I am against it, not because I am against trams. I would cancel it immediately. It would produce unacceptable effects on the residential side streets up and down the Uxbridge Road. The money could go into other plans.

Norris: I would scrap it on day one. The cure is worse than the disease. I wish Ken Livingstone had thought about the fundamental issue where does the money come from to build the tram? He has practically bankrupted Transport for London (TfL). He has no idea how to get value for money. He has spent £15million on consultation and that's just the waste you know about. He throws your money around like a drunken sailor.

Johnson: We are in favour of electric trams. I want trams to be liked and successful. In Croydon they have been successful. In Europe they are absolutely everywhere, it has been accepted as part of the way of life. I am sure the same will happen here. But the consultation has been handled very badly.

Do you support Barnet's policy of road hump removal?

Hughes: I have only one overriding view on how local councils deal with their traffic management: we have got to bring down the number of deaths on the road. Road humps are not necessarily better at dealing with that than other things. The Greater London Authority (GLA) report on traffic calming, made clear that road humps are not the panacea. Personally, I would prefer other things to road humps. Where there are alternatives that is a good thing.

Johnson: I don't think that road humps are the answer to everything and I don't think they should be inserted everywhere. But Barnet & Camden GLA member Brian Coleman seems to be on an ideological mission. I would also have withdrawn the funds from Barnet. I think we can be more inventive. We want cameras in home zones to implement 20mph limits.

Livingstone: I would much rather see traffic speeds in residential areas enforced by speed cameras but until we can change the law to do that, it is wrong to remove the only thing we've got. Eventually someone will be killed. When there is a fatality the relatives may take legal action for criminal negligence against Barnet and we would support them in that. Over the year there has been a clear divergence between what has happened in the average London borough and what's happening in Barnet, which is settling into the pattern of having an extra accident a week. It's criminally irresponsible for what is essentially a political gesture.

Norris: The whole question of being for or against speed humps is the wrong question. I approve of much of what is being done in Barnet. Areas where drivers will be driving at 30mph are the wrong place for speed humps. Coleman is right to say they should come out. But I don't think that having high speeds in residential areas is desirable. In home zone areas where the presumption is 20mph then point-to-point camera technology can be employed. But in continental Europe they do a lot more around tree planting, chicanes and removing road markings. By planting trees you block drivers' sight lines and it means they will not accelerate.

What policies are important for the Tube and trains?

Johnson: I think we are only going to have a sensible Tube and rail network if we bring it back into public ownership. Tube privatisation will be a disaster. I am pushing for full accessibility of Tube and rail network for disabled people by 2020. I am also very keen on the East London Line extension. It is a scandal that it has been neglected. I would link it up as part of an orbital rail network: an outer circular line. Most of the existing track is in place so it is possible. The Government has indicated the Mayor of London will have strategic powers over the commuter rail service. I totally agree, but when the franchises end they shouldn't be farmed out for privatisation.

Hughes: Although the Mayor doesn't yet have responsibility for suburban railway stations, making those more pleasant and safe is a priority. I would like the Mayor to have control over them. Every station should have a facility for you to buy all the tickets you need. We need a police presence at rush hour. We want late-night running Tubes on Thursday, Friday and Saturday. In return we are agreeing that there would be a week in summer, in August, when you close the line to the public in order to do all the maintenance in one go. You will need an overground or bus service, but we will have a much more reliable service in London if we can do that. I want a cheaper fare for people who finish their journeys before 7.30am.

Norris: I would install air conditioning on Tubes to make journeys more pleasant, run Tubes until 3am at weekends and establish a guards carriage after 10pm for people to feel safer travelling home at night, especially women. The Mayor should have responsibility for London's transport system and work to ensure passengers get the best service whether on Tube, train or bus.

Livingstone: Control over the Tube was passed to me in spring 2003. During this short period London Underground has made a priority of reducing average waiting times, improving customer information, including straightforward displays in every station showing services on every Tube line. Crime on the Underground was down by 55 per cent last year. One of my key pledges for the next term is to run the Tube later on Friday and Saturday nights, which means negotiating changes to the working hours of the private contractors. Control of overground rail services in London remains with the Strategic Rail Authority. However, I have set out a strategy for a London Metro service and will continue to argue that London should have a strategic rail body to oversee commuter services.