Transport for London is consulting on a proposal that, from 1 March 2027, it would no longer accept applications for new exhaust abatement systems, or for new alternative-fuel conversions such as liquefied petroleum gas and compressed natural gas, for taxis and private hire vehicles. The consultation runs until Wednesday 2 December 2026. It is not a decision.
The proposed stop applies to new systems. The consultation states: "Existing system approvals will remain valid and available to vehicle owners."
A vehicle already fitted with an approved system would continue to be licensed until it reaches the age limit that applies to it, provided it still meets the conditions of that approval and the other licensing requirements. Approvals already granted would remain in place, and vehicles already fitted with them would be unaffected. Because an existing approval would remain available to owners, the proposal does not set a final date for fitting a system TfL has already approved.
The TX4 approval
TfL's emissions standards for taxis, and TPH Notice 08/25 dated 18 December 2025, record that in July 2025 it approved a selective catalytic reduction exhaust system developed by HJS Emission Technology Ltd for London Taxi Company TX4 taxis that meet Euro 5. The approval followed two independent emissions tests and a 10,000-mile durability trial replicating a typical London taxi duty cycle.
A London-licensed Euro 5 TX4 fitted with that system, and delivering Euro 6 emissions, can remain licensed until it reaches a maximum age of 15, in accordance with other Euro 6 taxis. The emissions page sets the maximum for an eligible TX4 without the retrofit at 12 years.
One hundred retrofits
HJS Emission Technology reported on 24 September 2026 that it had completed 100 successful Euro 5 to Euro 6 TX4 retrofit installations. That total is the company's figure.