Company Car

Your Independent source of fleet news, reviews & interviews

CCT Knowledge Roundel - In association with ToyotaAn independent study by researchers from Imperial College London has highlighted the zero-emission capabilities of self-charging hybrids

A detailed new study by researchers from Imperial College London has unearthed surprise figures regarding the amount of time hybrid vehicles spend in a zero-emission state.

The research was carried out across a 33-mile test route in north London encompassing urban, semi-urban and motorway roads. Itfound that on 133 of the journeys conducted by a variety of male and female drivers totalling over 300 hours, the three latest-generation Toyota Prius and three Toyota Corolla models used in the study were in zero-emission mode for on average 77.1% of time and 51.6% of distance. Those numbers rose to 81.8% of time and 66.7% of distance in urban use.


As powertrains develop and all manufacturers look to electrify, the different types of technology increase.

Traditionally, fleets had a choice of petrol or diesel power. Now that ranges across hydrogen power, pure electric, plug-in hybrid, self-charging hybrid and mild-hybrid petrol or diesel – as well as the internal combustion engine.

Mild hybrids in particular, which use a very small battery to run ancillary operations, are considered by some brands as electrification of their models, even though the battery isn’t actually capable of running the car in isolation.

“I think there’s a bit of confusion in the market where there are so many vehicles called hybrid, and we’ve still got some way to go to make sure that everyone understands how our hybrid works,” says Toyota and Lexus fleet boss Stuart Ferma.

As far as regular full hybrids are concerned, these models don’t need plugging in, and are capable of powering the vehicle on their own for short periods, before recharging via brake regeneration or using the car’s engine to replenish the battery.


The electric motor powers the car at low speed and on light throttle, such as when in a city.

Some hybrids are more hybrid than others: 1 - Pulling away from a stop

Pulling Away

This is where the petrol engine is most efficient, so it is used at higher speeds. At cruise, the engine also powers the generator, producing electricity that is stored in the battery for later use.

Some hybrids are more hybrid than others: 2 - During normal cruising

At crusising speed

The petrol engine and electric motor work together to give maximum power.

Some hybrids are more hybrid than others: 3 - Under heavy acceleration

Under heavy acceleration

When the accelerator is left alone, the system’s regenerative braking system takes energy from the rotating wheels to power the generator, topping the battery back up for use later.

Some hybrids are more hybrid than others: 4 - During braking and cruising

Under braking or freewheeling

Both the petrol engine and electric motor switch off and the car uses battery power to operate lights, radio, air conditioning etc.

“We gleaned some really powerful information from this,” Toyota and Lexus’s general manager fleet Stuart Ferma (pictured below) tells Company Car Today. “While diesel still has its placae, we would argue in light of this data that the same now applies to hybrid.

Stuart Ferma, Toyota & Lexus General Manager - Fleet

“That’s why we believe that hybrid is the absolute answer for fleets and company cars, certainly for the next number of years, because you don’t have to plug it in, you don’t have to worry about infrastructure, it delivers low CO2, which helps with benefit-in-kind and it helps to assist in cleaning up cities because it’s a lot cleaner in the city environment than would be a diesel engine,” he adds.

Toyota’s hybrid system works by combining a small 1.3kWh battery with a petrol engine, deploying only the electric motor when pulling away in city driving, up to 15mph, but using the petrol engine during normal cruising, when it’s at its most efficient. The battery can power the car for up to around a mile at a time, replenishing either using the engine or via regenerative braking.

Knowledge - Study Reveals Hybrid Benefits - Graphic - Zero Emission Usage Average Results

On 133 circuits of a 33-mile test loop in London, the three Toyota Prius and three Toyota Corolla hybrid models returned the following average results for zero emission usage.


The speed at which the battery charges and is available to redeploy has previously been debated, and the study by Imperial’s researchers laid bare the system’s efficiencies. That study also backs up the results previously observed in similar trials in Rome, Paris, Dublin, Madrid and Darmstadt.

“The results show that full hybrid vehicles are extremely effective at reducing emissions, and our results were robust to sensitivities including time of day, driving style and use of air conditioning,” says Dr Marc Settler of Imperial College London, working independently via Imperial Consultants. “When considering all the times when the engine is off during a given journey this demonstrates a really significant effective zero emissions range that’s ideal for urban driving.”

A Toyota spokesman adds: “We’re now on the fourth-generation system, and if you go back to say 2000, if you needed to cover distances then diesel was probably the better choice, but what we’ve seen in these tests is that parity is much closer with hybrids; we now say it’s comparable.”

Knowledge - Study Reveals Hybrid Benefits - Graphic -Independent Research Results Carried Out in Other European Countries

The results echoed similar independent research already carried out in other European cities. The figures represent the amount of time and distance undertaken with zero emissions.

The brand recently announced it was discontinuing the petrol versions of the Corolla and C-HR models, taking them petrol-hybrid only, as is already the case with the RAV4. “Toyota isn’t just going down the hybrid route, but it is a core part of our strategy and has been for a number of years because it’s a practical solution that delivers great cost of ownership,” says Ferma. “Hybrid has fewer components that need to be replaced so needs less maintenance and saves money for the driver because of the BiK element. And you don’t have to charge it. It delivers everything you need today; it’s a normal car, it just has different technology.”

Toyota’s fleet boss admits that in the early days of hybrid, having launched the first Prius as far back as 1997, the company struggled to earn the place in the company car sector that it believed hybrid technology deserved.

“It was a challenge selling hybrid into a diesel market for a number of years, and what we got during that period was fleets that wanted to be green, rather than thinking they had to be green,” explains Toyota’s fleet boss. “We’ve seen it expand from fleets that really took their green message very seriously and now we’re seeing opportunities with company car drivers, essential need fleets and salary sacrifice. Across the board people are coming to talk to us about hybrid now.”

Ferma also says the public sector is one area of particular interest in hybrid tech. “They’re in a really interesting place. They’ve got a really big diesel fleet and they’ve been told to electrify it. That’s the journey and we’re helping them with it. They have pressures on cost, so not all of them can adopt an electric vehicle.”

Toyota uses the example of first responder or paramedic fleet deployment, which need four-wheel drive and plenty of space. That’s why the RAV4 off-roader works well because it provides a hybrid solution compared with the traditional diesel options.

And that trend is, Toyota says, continuing off the back of the current social and political climate, primarily around the focus on local air quality and low emission zones; both Toyota and Lexus have enjoyed significant recent true fleet growth.

“With air quality and all the problems in cities, it seems that the planets have aligned,” says Ferma. “Hybrid is an answer for today, and you can see from the studies that it really does help in terms of the time and distance on zero emissions mode.

“Clearly, air quality is going to be helped where there are no emissions coming out of the vehicle. We see hybrid as the right answer for today.”


Toyota has nearly doubled sales of its hybrid models over the past four years, and the brand accounted for two-thirds of the 97,850 hybrid electric vehicles registered in 2019, according the Society of Motor Manufacturers and Traders.

Knowledge - Study Reveals Hybrid Benefits - Graphic - Toyota's Hybrid Sales TrajectoryAnd while the overall new car market was down 2.4% year-on-year, hybrids were up 17.1% on 2018.

That popularity is also feeding through to the used market. “We have seen a rise in demand for used hybrids and alternatively fuelled vehicles (AFV) over the past few years as drivers are looking at their impact on the environment,” says Chris Plumb, senior valuations editor at Cap HPI. “The demonisation of diesel, the introduction and talk of clean air zones and lower running costs has put AFV and hybrids on the used buyer’s consideration lists.”