What Is the Difference Between a TX4 and a TX5 Black Cab?

Two generations of London cab share the city’s streets today. The older TX4, built by LTI between 2007 and 2017, runs a diesel engine sourced from Ford or VM Motori that drives the wheels directly. Its successor, the LEVC TX5, works differently: an electric motor handles propulsion, while a Volvo-built petrol generator tops up the battery as a mobile power station. That single change drops emissions sharply and sidesteps London’s congestion charges.

Engineering and Powertrain Shifts

Classic London motoring lives on in the diesel cab. You see these vehicles everywhere near Victoria Station or Heathrow. Most units built between 2007 and 2017 by LTI rely on diesel combustion, paired with a heavy gearbox to manage torque. The engine note is distinctive. It vibrates through the chassis when idling at a red light on Oxford Street.

These cabs are loud. Drivers put up with real vibration during long shifts across South London. Frequent maintenance keeps the diesel engines inside tightening Euro emission limits. Reliability stays high. Mechanical simplicity, though, cannot match a modern electric drivetrain.

Everything changed in 2017, when the electric model arrived with a range-extender system. A petrol engine generates electricity rather than turning the wheels. That setup allows near-silent cruising through quiet residential areas like Richmond, and the electric motor takes the strain in stop-start traffic.

Efficiency is where the gap shows. Where the older cab burns diesel constantly, its replacement routes energy through a battery pack. Cost per mile falls sharply for professional drivers. We find the fuel savings often offset the steeper purchase price.

Quietness is the first thing passengers notice.

Visual Design and Economic Realities

Spotting the difference takes a second. The diesel cab carries a rugged, boxy silhouette, with visible rivets and separate headlight units that make it look like a working tool. Its successor wears flush body sides and integrated headlight clusters for a much smoother profile, closer to a modern passenger car.

Interiors tell the same story. Passengers get a more refined cabin in the newer cab compared with the utilitarian feel of an older LTI model. The doors even close with a different weight. Light catches the curved panels in a way the flat diesel-era surfaces never managed.

Economics drive the whole transition. A used TX4 might cost a driver £10,000 to £15,000 on the second-hand market, an accessible entry point for new operators. A new LEVC, by contrast, runs to roughly £60,000, a figure that demands serious financing or high daily takings to justify.

Regulation sets the clock. A 15-year age limit applies to most diesel cabs under current rules, which means the majority of these icons retire by 2026. Drivers either adapt or leave the trade.

The changeover is already well underway.

Frequently asked questions

Does the TX5 run entirely on electricity?

No, it uses a range-extender. The petrol generator kicks in to charge the battery when levels get low. This prevents the driver from running out of power during long trips to places like Gatwick. It functions as an electric vehicle with a safety net.

Is the TX5 exempt from the Congestion Charge?

Yes, it currently qualifies for exemptions that the diesel TX4 does not. This saves a driver roughly £15 every single day they enter the central zone. These savings are vital for maintaining a profitable business in London.

Which taxi is better for wheelchair users?

Both models are fully wheelchair-accessible. The TX5 offers more modern interior space and easier ramp deployment due to its newer chassis design. However, the TX4 has a long history of reliable service for passengers with mobility needs.

Can I buy a new TX4 today?

You cannot. LTI stopped production of the diesel TX4 years ago to make way for LEVC models. You can only find them as used vehicles through specialist dealers or private sales. Most remaining units are quite old.

Why did LEVC switch to electric?

The shift responds to London's Ultra Low Emission Zone (ULEZ) requirements. Diesel engines struggle to meet these strict environmental standards without expensive modifications. Electric powertrains allow drivers to operate in any part of the city without extra penalties.

How much does it cost to fuel a TX5?

Fuel costs are lower per mile than the diesel TX4. Because the petrol engine acts only as a generator, it operates at its most efficient RPM. This reduces wasted energy compared to a traditional engine idling in heavy traffic.