He travelled by train to York to visit the Switch Mobility factory on the outskirts of the city, which has provided 67 electric buses to the capital, with a further 30 being built.
Mr Khan said the purpose of his day-trip was to “build bridges” between London and the regions and showcase the capital’s role in the “levelling up” agenda.
But some observers suspected it was also part of his wider aspiration to eventually become Labour party leader by building support nationwide.
Mr Khan also penned a column for the Yorkshire Post – a week after Greater Manchester mayor Andy Burnham, seen as his main long-term rival to make it to Downing Street, agreed to become an Evening Standard columnist.
There are more than 500 electric buses in the capital, and this is expected to increase to 700 - out of a fleet of 9,000 mainly diesel vehicles - by the end of the year.
Mr Khan wants to make all London buses zero-emission by 2030 but needs substantial Government funding to enable this to happen.
Mr Khan said: “When I was signed-in for my second term I pledged to build bridges between London and the rest of our country and to showcase how London can help the national recovery and the levelling up agenda.
“This Yorkshire factory, which is manufacturing state-of-the-art electric buses for London, shows how investment in our capital can help create quality green jobs across the country.
“Too often, the need to ‘level-up’ cities and regions across the UK is wrongly presented as a need to ‘level down’ other parts of the country, such as London – but that is in nobody’s interest. When London succeeds, the UK succeeds and vice versa. London is ready and willing to play its part in ensuring a strong and green national recovery from this terrible pandemic.”
Switch Mobility estimates that around 50 per cent of its revenue last year was from TfL contracts. About 85 per cent of its order book this year is with TfL.
All London buses now meet the Euro VI emissions rules following a retrofitting programme to replace engines in older buses with cleaner ones.
Electric buses are cleaner, quieter and have fewer vibrations. They are expected to be introduced this month on route 200, which operates between Raynes Park and Mitcham, and 65, which operates between Ealing and Kingston.
Single decker electric buses were first introduced in 2016 on routes 507 and 521, while electric double decker buses began to be introduced in autumn 2019 on routes 43 and 134, followed by route 94 in February last year.
The problem with fully electrifying London’s bus fleet is the need for bus depots to upgrade their power supplies.
This is costly and the private firms operating London’s buses typically need to win a new electric bus contract, rather than just having an existing diesel route upgraded to electric vehicles, to make it financially viable.
TfL says the cost of this is approximately £180m, which would ultimately have to be paid through the tendering system over time if the entire bus fleet is to be electrified.
However the electrification of the network is estimated to deliver fuel savings of more than £200m annually by 2030.