Last reviewed 14 May 2019

On 8 April 2019, the London Ultra-Low Emission Zone (ULEZ) came into effect covering the same area as the Congestion Charge and with stricter emissions standards for heavy vehicles than the existing Low Emission Zone (LEZ).

In other towns and cities, Clean Air Zones (CAZs) with differing restrictions are supposed to be introduced by the end of this year.

Meanwhile, the London Borough of Hackney has separately introduced two zones that it calls “ultra-low emission streets” or “ULEV streets” with completely different standards and Oxford City Council has plans for what it calls a “zero emission zone”. In addition, it is proposed that conventionally-powered vehicles should be banned from sale by 2040 or even sooner.

Richard Smith looks at ultra-low and zero emission technology and the likely issues.

Ultra-Low and Zero Emission Vehicles

While conventional vehicles continue to be defined in terms of their type approval emission standards, these new classes of vehicles are defined not in terms of their output of the conventional pollutants (CO, HC, NOx and PM) but in terms of carbon dioxide (CO2) output.

  • Ultra-Low Emission Vehicles (ULEVs) are vehicles that produce tailpipe CO2 emissions of 75g or less per kilometre.

  • Zero Emission Vehicles (ZEVs) produce zero tailpipe CO2 emissions.

As the definition suggests, a ULEV still has an internal combustion (IC) engine but this is typically married with an electric motor to produce a hybrid vehicle. Hybrid vehicle may be of different types according to the way in which the IC engine and electric motor work together.

  • Parallel Hybrid Vehicle — a hybrid vehicle in which the IC engine and electric motor both work together to provide the power that drives the wheels.

  • Series Hybrid Vehicle — a hybrid vehicle in which the electric motor is the only means of providing power to the wheels. The motor receives electric power from either the battery pack or from a generator run by a gasoline engine.

  • Series/parallel Hybrid Vehicle — a hybrid vehicle that combines the principles of both series and parallel hybrid, ie the vehicle can be powered by the IC engine and electric motor combined or by the electric motor alone.

In addition, any of these types may be a “self-charging” hybrid vehicle, where a relatively small-capacity battery is charged by the engine under light load conditions and by regenerative braking, or a “plug-in” hybrid electric vehicle (PHEV) with a larger battery that can be also charged when the vehicle is static through a connection to the mains supply. In either case, the addition of the electric motor means that a smaller IC engine can be used, with lower fuel consumption and CO2 output, and some battery-only running.

True ZEVs have no IC engine and are powered entirely by an electric motor.

  • A Battery Electric Vehicle (BEV) derives the energy to drive the electric motor from an on-board storage battery and the range is therefore limited to the capacity of that battery and any contribution from regenerative braking. Regular static recharging is therefore required.

  • A Fuel Cell Electric Vehicle (FCEV) also uses an electric motor as its sole power source, but the electricity supply comes not from a storage battery but from the electrolysis of hydrogen gas. The gas is stored in a tank on the vehicle and converted to electricity in the fuel cell. This electricity then powers the electric motor directly. When the hydrogen tank is empty, it is refilled exactly as with a conventional fuel tank.

Hybrid vehicles — disadvantages

While hybrid vehicles were once a must-have for any environmentally-conscious celebrity, they have recently fallen out of favour with environmentalists, with suggestions that some of them should be included in any ban on the sale of conventional vehicles. As they use an IC engine for at least some of the time (possibly most of the time in real life) they still produce the same range of emissions as conventional vehicles and are still subject to Euro 6/VI regulations. Real Driving Emissions (RDE) testing since late 2018 has resulted in some being recategorised in terms of CO2 emissions to the extent that they are no longer eligible for subsidy in Europe. In fact, the RDE test probably still does not replicate real long-distance use where the electric range will be a tiny proportion of the whole.

Zero emission vehicles — disadvantages

Battery-powered cars and vans have developed a great deal, to the extent where some can operate for two hours with a 20-minute recharge time. This is an entirely acceptable cycle, but the problem remains the recharging infrastructure. For present numbers, there are sufficient fast charging points but as the number of vehicles in service grows, these will need to increase to the point that, for example, every public parking space will need its own charging point. The idea of rapid swapping of a discharged battery for a fully charged one at a service station seems unattainable given the size and weight of battery necessary (around 2m2 and half a tonne for a Tesla) and the fact that the demands of styling dictate the need for bespoke installations.

FCEVs can be refuelled as quickly as filling a tank with diesel if the refuelling infrastructure is provided. This is not yet the case, though it could be, and these vehicles look like the answer at the moment.

However, there is a more fundamental problem with both BEVs and FCEVs in that while both offer zero emissions at the tailpipe that simply moves the emissions problem further back down the line since both technologies rely on the generation of electricity in the first place, either to charge the battery or to produce the hydrogen. With the decommissioning of hydrocarbon-fuelled power stations, the hope is that all our electricity needs, including this huge new demand, will be generated by so-called “renewable energy” sources (wind and solar) that are notoriously uncertain with regard to the amount available at any given time. It is fair to say that reliance on such unreliable sources will lead to the almost certainty that at some stage demand will outstrip supply and large-scale blackouts will occur.

What does it mean for haulage operators?

As things stand at the moment, the suggested ban on sales of conventional vehicles (including some hybrids) does not affect operators of haulage operators because there are (yet) no suggestions that large goods vehicles should be included in the ban.

While hybrid goods vehicles are available, there seems little point in starting down this road since:

  1. the amount of CO2 produced in any combustion engine is directly proportional to the cylinder capacity and no IC engine capable of providing the power needed to propel a large goods vehicle could ever be small enough — even with electric assistance — to get below a 75g/km CO2 threshold

  2. any Euro VI versions already in use may see out their economic life.

Neither can battery electric technology provide the power, the range and the certainty of availability required for these and other critical-use vehicles in the foreseeable future, irrespective of the other problems noted above.

  • In the shorter term, certainly over the next one or two replacement cycles, the current generation of diesel-powered heavy vehicles (Euro VI) will almost certainly meet any requirements and any earlier specification vehicles should certainly be replaced (there are currently no proposals for a Euro VII standard). Indeed, there is no possible alternative for vehicles at the top end of the gross weight range.

  • In the medium term, the answer appears to be the hydrogen fuel cell and, subject to appropriate bunkering facilities, maybe the answer now where the highest gvw is not required. Hyundai has contracted to supply 1000 fuel cell lorries to Switzerland over the next five years and while these are only 2-axle, 18-tonne vehicles (34-tonne gross train weight), Toyota has a 36-tonne articulated combination at an advanced stage of development in the USA.

  • For further details on what operators can do, go to the Control of Emissions from Vehicles topic.

The background to these latest initiatives

The reasons for these initiatives outlined above are both straightforward and complex. Straightforward because the adverse effect of combustion products on air quality and health has been well understood and tackled for a very long time (even before the advent of the IC engine) and exhaust emissions have been regulated in the USA since the beginning of the 1960s and in Europe since 1970.

Having got a firm control of the toxic emissions, particularly after 1991 with the introduction of the Euro 1 and subsequent regulations, governments got distracted by the spectre of anthropogenic global warming, caused by CO2 and focused on policies to reduce CO2, including tax incentives to switch to diesel engines for cars on the grounds that higher-efficiency diesel engines tend to produce less CO2. What seems to have been forgotten was that diesel engines by their nature also produce NOx and PM, neither of which features much from the petrol engine.

Thus, policies to combat global warming have encouraged a huge increase in light-duty diesel vehicles in use and subsequently, urban air quality took a steep decline. The response to this has been to swing back abruptly in the other direction, with tax incentives abruptly replaced by tax penalties and international commitments to “de-carbonise” the economy by 2050. In support of this, governments have announced a ban on sales of conventional vehicles by 2040, with some suggesting this needs to be sooner, maybe by 2030. Such vehicles would be replaced by ULEVs and ZEVs.