Ken Livingstone says the fear of crime is overstated, violent crime is coming down and blamed a hardcore of gang members for the 26 teen murders in the capital last year.

He said the 26 murders had to be kept in perspective of the capital's population of more than one million young people.

Mr Livingstone said the capital had enough police and the neighbourhood beat bobby system was working well.

He said he was working hard to bring down crime.

He pointed to measures including issuing police with hand-held crowd scanners to detect concealed weapons in the next six to nine months.

The scanners will mean police can arrest weapon carriers without thousands of personal searches.

"There will be teams of armed police who will be able to arrest them there and then," Mr Livingstone said.

Answering questions posed by readers on yourlocalguardian ahead of the May 1 mayoral election, Mr Livingstone said he was tackling heat on the Tube by air-conditioning carriages and cooling platforms.

He said new District Line carriages would be air-conditioned.

Deep lines like the Northern Line could not carry air-conditioning units on the outside of carriages so engineers were instead testing pumping ground water under platforms to cool the whole system.

"Most of the heat is from the braking system," Mr Livingstone said.

The underwater cooling is now being trialed at Victoria station.

He said Transport for London was looking at improving Northern Line services by using a loop at Kennington to turn trains around.

The quicker turnaround would allow for more services, he said, but the scheme will not be in place until around the Olympics in 2012.

Mr Livingstone said the congestion and emission charges would not increase traffic through Wimbledon, Wandsworth and other areas across south-west London.

He said most drivers hit by the emission charge lived within the zone and drove within it.

"The people with the four-wheel drives are in the centre and they stay in the centre," Mr Livingstone said.

"You don't get people jumping in their Ferraris and coming down to Sutton for a Friday night rave."

He also denied small businesses would suffer because of the emission charge due to hit vans in 2010.

He said vehicles built after 2002 would be exempt from the charge and the phase-in gave business owners enough time to update their vehicles.

Asked when train operators would be installing Oyster readers, Mr Livingston said it was "a scam" that train operating companies (TOCs) had failed to install them earlier.

But he said there was agreement from TOCs to set a date in early 2009.

He said Oyster was available on the London Overground, which is run by Transport for London, which had doubled revenues on the line.

He said he offered to pay £25million to TOCs to help put the Oyseter in. He said: "For too long the train companies have been concentrating on people who make genuine mistakes on their fares. It is a scam."