Restricting the use of large heavy internal combustion vehicles on our roads can have a dramatic effect on our consumption of fossil fuels and the generation of both CO2 and a range of damaging pollutants in the urban environment.
There is broad agreement among scientists that climate change and rising levels of CO2 in the atmosphere are linked. Only by reducing CO2 generation might we stabilise and hopefully reverse some of the effects we associate with climate change. Governments across the world set targets but it is absolutely essential that we do as much as we can sooner we can and not wait for “the authorities” to actually do anything. It’s just too important.
In the UK a major part of our energy consumption is the petrol and diesel fuel used for transport. Climate change activists insist there should be wholesale movement away from private cars to walking, cycling and public transport. Walking and cycling is fine for those who are young, fit and healthy and preferably live in a flat city. Make sure you don’t have small children or a lot of shopping to carry and certainly don’t live in a country with often pretty ghastly weather. Public transport is often little better than taking us from somewhere we are not to a place we don’t want to be at a time that is inconvenient. For many, these aspirations are a bit like St Augustine’s famous words “Oh, Master, make me chaste and celibate-but not yet”. Many activists are happy to encourage others to make changes but are somewhat slower with their own responses. Few have the dedication of Greta Thunberg!
We Love Our Cars!
The motorcar has given vast numbers of people the capacity to be mobile, to go where there are jobs, shops and entertainment. It allows families to travel together and it is naïve to think that a society like ours will give up this capability quickly or easily. It doesn’t have to but it does have to be managed. Ultimately widespread availability of low-cost electricity from renewable sources will help greatly but in the meantime there is a lot that can be done now to accelerate these changes and deal with two major problems we have now: consumption of fossil fuels and urban pollution.
How big is the problem? There are approximately 31.5 million cars (82.5%), 4 million vans (10.5%) and 0.5 million heavy goods vehicles (1.3%) in the UK (from DoT, 2019). In total they generate about 120 million tonnes of CO2 per annum (UK DoBEIS, 2019). The weighted average combined fuel economy of cars and light trucks in 2016 was about 22 miles per gallon and the average vehicle travelled about 11,500 miles per year. The fuel burned within the engine generates the heat used to propel the vehicle. There have been significant improvements in engine efficiency in recent years but it is still the case that typically 25% of the energy actually propels the vehicle. The remainder is heat which is dissipated through the exhaust and cooling systems of the vehicle. Electric vehicles transfer the pollution away from the vehicle to where the power is generated. If the source is renewable then the pollution produced is low. The efficiency of electric motors is very high indeed and, particularly if breaking regeneration is used then electric vehicles are dramatically more energy efficient than fossil fuel. The spin around renewable power is somewhat different from the reality. About 30 % of electricity generation is currently renewable, but it’s only less than 12% of the energy provided by petroleum (petrol plus diesel). Building eight times as many wind farms or solar panel farms would be an enormous investment and take many years. However it turns out there is a great deal we could do now to halve the energy used for transport.
Motor vehicles are also responsible for another major problem, that of pollution particularly in the urban environment. That pollution is a combination of exhaust fumes, both gas including CO2 and nitrous oxide as well as particles from diesel and from the tyres which inevitably wear away on the road surfaces. In several British cities pollution levels regularly exceed permitted safety levels. In addition, surveys indicate that the noise from vehicles significantly affects the quality-of-life of around 30% of people in the UK.
Heavy Vehicles Waste Far Too Much Energy
Now for a bit of physics. The energy used by a vehicle allows it to accelerate. The energy needed to double the speed of a vehicle goes up in proportion to the square of that velocity so it takes four times as much energy for a car to reach 60 mph as it does to reach 30 mph. Once it has reached cruising speed a significant part of the energy is dissipated to overcome wind resistance. The kinetic energy of the vehicle is reduced whenever the brakes are applied and that energy turned into heat which is wasted. In the UK the average length of a single trip for a vehicle is only about 8 miles. 85% of trips are less than 10 miles and 95% are less than 25 miles. A typical trip involves several acceleration/braking cycles wasting considerable amounts of energy and therefore generating considerable amounts of CO2.
Typical cars sold in the UK now weigh up to 2.5 tons. That weight has crept up in recent years because of the popularity of larger SUV type vehicles offering bigger load carrying capacity as well as greater levels of comfort. Most journeys only involve a driver with possibly a single passenger contributing an almost negligible additional weight to the total. Older readers may remember how cars became much more sluggish when laden with three or four passengers. This is not something most drivers experience these days now that cars are bigger, heavier and more powerful. Every additional kilogram requires additional energy to accelerate it. Reducing the weight of the vehicle will improve its energy efficiency markedly. A mass move from internal combustion propulsion to electric will take very many years to complete. I will argue that motorists and city planners need to do their bit to encourage strongly the use of smaller electric vehicles. This is something that can be done simply by banning internal combustion and bigger vehicles from inner-city regions where pollution and noise are problems.
In the UK the average car is over 8 years old. Worries surrounding Brexit have reduced new car sales significantly so we can expect a jump in sales once Brexit is resolved. Anything you can do by choosing a lighter, smaller car next time or persuading others to do so will make a significant contribution towards reducing our national carbon footprint.
Small Electric Vehicles Are Increasingly Attractive
Most of the electric vehicles manufactured today are expensive and targeted at the luxury end of the market. They are big, heavy and although electric still consume unnecessary levels of energy. Cars used to be much smaller but would this be at all practical to move to much smaller electric vehicles? Small, efficient all electric cars are already in production. Manufacturers greatly prefer to sell large vehicles with big engines. Many have already produced all electric variants on their main ranges but surprisingly little effort seems to be going into making much smaller vehicles. One exception is the Mitsubishi i-MiEV introduced 10 years ago. This is a five door hatchback weighing only one ton. It has a 16 kWh battery giving it a range of up to 100 miles. The ability to go for 5 miles on one kWh can be compared to the typical level that we get on a modern car of about 1 mile/kWh. the Mitsubishi vehicle can carry four. An even smaller all electric vehicle that can carry two and is less than half a ton in weight is the Renault Twizy, currently selling for around £7000 in the UK. It has a range of about 60 miles with a 6kWh battery giving a consumption of around 10 miles/kWh, a tenfold improvement over a typical modern car.
Reducing the mass of our cars has a dramatic effect on our national energy consumption. If we imagine replacing our cars with others half a ton lighter yet continuing to drive them in the same way we do now we would reduce U.K.’s energy consumption by 10%, cutting CO2 production by 40 million tonnes per year, saving each of us perhaps £800 per annum. If we all managed to reduce the weights by a full ton it would cut option by 20%, reducing CO2 production by 80 million tonnes per year.
Persuading People to Change Their Habits.
What could be done to encourage and indeed accelerate the move towards such a reduction in energy consumption as well as effecting a substantial reduction in pollution that damages so many urban environments? It should be clear from the above that encouraging the use of smaller and lighter vehicles would make a great difference. Further, requiring that these smaller vehicles were either fully electric or hybrid so they could be operated without liquid fuel would be even more effective. The most direct approach is to plan a phased tightening of the controls on vehicles entering and being driven around key urban areas. Start by limiting larger and heavier vehicles so they cannot be driven around in the restricted urban area. Next insist on electric/hybrid operation exclusively initially during core busy hours but eventually at all times. The size limitations could be progressively tightened. One of the key features must be the development of substantial pressures on automotive manufacturers to produce small light and economic city vehicles. At present electric/hybrid vehicles are very much positioned at the top end of manufacturers range rather than at the bottom end which is where there will be most impact.
There is even more that can be done. City cars do not need to be built to reach 80 mph (as does the Mitsubishi one above). Having a lower overall performance allows the vehicles to be made even lighter and cheaper as well as being more reliable. Electric motors give good silent acceleration but city cars don’t need to exceed 50 mph. The cost of these vehicles will be key to ensuring that they become generally acceptable and eventually highly desirable. There will be considerable opposition to these moves from oil companies, automotive manufacturers and parts of the public who feel their divine right to drive a vast vehicle through the centre of our ancient cities must not be violated. However we can only deal with climate change if we genuinely start to make changes like this. It is not a complete solution but it is a start. Many realise that it’s just not enough to be careful with plastic waste. All around us we can see that the motorcar is a significant part of our problems and this is how we can start to manage it in a way that will work for the UK.
