TfL applies cautious assumptions to plug-in hybrid emissions in London modelling as push for zero-emission taxis and PHVs

Transport for London (TfL) uses real-world emissions factors in its emissions inventories and only recognises emissions benefits from petrol plug-in hybrid cars at lower speeds, the Mayor has said, citing uncertainty over how the vehicles perform in practice.

The response came after City Hall Green Zack Polanski asked Mayor Sadiq Khan how the Greater London Authority and TfL account for the risk that plug-in hybrids emit more carbon dioxide in real-world use than manufacturers’ official figures suggest.

Polanski’s question referred to an International Council on Clean Transportation study, Fair game: Restoring technology neutrality through plug-in hybrid utility factor adjustment. It found that newer plug-in hybrids in Europe had higher average real-world CO₂ emissions despite offering longer electric ranges.

The Mayor said TfL’s emissions inventories use industry-standard factors based on real-world testing known as COPERT. He added that TfL continues to review emerging evidence, including the ICCT study.

In response to the uncertainty, the Mayor said the “best way to remove uncertainty is accelerating the transition to fully electric vehicles”, which he described as central to London’s air quality and net-zero ambitions.

For the taxi and private hire vehicle sector, the response points to a commitment in TfL’s Taxi and Private Hire Action Plan 2025 to consult on zero-emission requirements for newly licensed vehicles.

The policy could affect future vehicle choices for taxi and private hire drivers and operators, depending on the scope and timing of any requirements. The response did not identify how existing licensed vehicles would be treated.

The Mayor also said London has a third of the UK’s charging points and that more than 3,000 London buses are fully electric. He said the GLA and TfL are enabling EV charging infrastructure on their land where possible.

The Mayor added that his actions to tackle air pollution had helped deliver an estimated 40 per cent reduction in deaths linked to air pollution between 2019 and 2024.

Sadiq Khan said: “I am proud of my actions to tackle air pollution, helping deliver an estimated 40 per cent reduction in deaths linked to air pollution between 2019 and 2024.

Transport for London (TfL) uses industry-standard emissions factors in emissions inventories, based on real-world testing (“COPERT”) and only considers emissions benefits of petrol plug-in cars at lower speeds, reflecting uncertainty. TfL continues to review emerging evidence, including the ICCT study. 

“The best way to remove uncertainty is accelerating the transition to fully electric vehicles, which is central to my air quality and net zero ambitions. I am supporting London’s electric vehicle revolution by enabling EV charging infrastructure on GLA and TfL land for EV charging where possible. Already London has a third of all UK charging points, more than 3,000 London buses are fully electric, and TfL committed in the Taxi and Private Hire Action Plan 2025 to consult on zero-emission requirements for newly licensed vehicles.”