Public transport has taken centre stage in campaigning for London's mayoral elections as London mayor Ken Livingstone and his main rival, Boris Johnson, published transport manifestos.

With the May 1 election now just six weeks away, Johnson unveiled a range of policies relating to bus, rail and tube services.

Much of the attention was attracted to his pledge to scrap London's 400 articulated buses and launch a competition to produce a new "21st century Routemaster" with conductors.

Johnson said that articulated buses blocked junctions and caused collisions. When routes that operate articulated buses come up for renewal, Johnson said that his administration would specify a different type of bus.

Commenting on his plans for a 21st century Routemaster, he said: "Londoners want an iconic bus that they can identify with. Public transport is about more than just a series of numbers or targets. Londoners deserve buses that are reliable but also enjoyable to ride, safe, and moreover emblematic of our great city."

He said that his administration would aim to have new Routemaster, with conductors, running in London by the end of its first term.

Livingstone challenged his rival to reveal how many buses he planned to run with conductors. He claimed that it would cost £112m to introduce conductors on routes currently operated by articulated buses.

The mayor said: "Articulated buses are only 5% of the bus fleet in London and therefore Boris Johnson has pledged to increase the cost of running LondonÕs bus fleet by over £100m a year, requiring a 15% bus fares increases, in order to replace 400 buses."

Johnson also made other pledges relating to buses, including a trial of orbital express coach routes linking key rail stations in south London. He meanwhile promised to use London's bus tracking system to create an online, real time map of the location of every bus in London. Although £117m is being spent on the iBus project, Johnson said Londoners were being denied access to a live map of London's buses.

Bus operators will be concerned at Johnson's plans to enable motorcycles to use bus lanes, and his pledge to consult residents on whether to keep the western extension of the congestion charge zone. However, they will welcome his pledge to seek the power to fine utility companies that cause delays.

Turning his attention to rail services, Johnson said he would summon London's train operators to an emergency summit "to demand longer trains, manned stations at night, more frequent services and lower fares".

On the tube he promised longer opening hours on Fridays and Saturdays and a no-strike deal with the trade unions.

Meanwhile, he attacked the mayor's record on safety, pledging "police officers not press officer". He said he would introduce 440 extra PCSOs and 50 extra British Transport Police officers. He also attacked Transport for London commissioner Peter Hendy for claiming that buses are safe.

Speaking at the launch of his transport manifesto, Boris Johnson said: "We have had to sit and watch as fresh thinking and vital reports have been suppressed - all while this Labour mayor has pursued far-flung projects which are completely out of touch with Londoners' concerns.

"My vision is of a London that is not subject to the same old rigid approach, but is run according to new ideas and fresh thinking." Livingstone countered that his rival's proposals are misleading. "Boris Johnson's transport manifesto is unravelling every day," he said. "It has been shown to be completely uncosted, and must therefore be withdrawn.

"A new document with honest and accurate costs must be issued so Londoners can know what policies the Conservative candidate for mayor is presenting to them."

Unveiling his own transport manifesto, Livingstone said: "The biggest task confronting the mayor over the next four years is to successfully deliver the huge transport projects that are now under way in London - because these are the key not only to moving around the city but to the entire finances of London.

"Delivering the £16bn Crossrail project successfully, carrying through the £1bn a year tube modernisation, continuing the expansion and improvement of London's bus system seen in the last eight years and completing the upgrades and extensions to overground rail services, will transform London's publictransport for the better."