of the primary pollutants can be two to three times higher than the background urban level, while inside vehicles travelling along major roads, concentrations can be on average five times higher than the background levels (RCEP, 1994). Regional effects can occur far away from the source of the emission and affect wider geographical areas, sometimes spanning several adjoining countries. GHG emissions, on the other hand, affect the global atmosphere. The same pollutants, such as sulphur dioxide or nitrogen dioxide, can have an adverse effect on the environment over differing distance ranges.
We turn first to the global effects as they have become the main cause of environmental concern. This is partly because scientific discoveries over the past two decades have revealed the severity of the climate change problem, but also because tightening controls on the emissions of other noxious gases have eased pollution problems at local and regional levels.
equivalents (CO2e), which are calculated by multiplying the mass of a given GHG by its GWP. CO2e is a unit used for comparing the radiative forcing of a GHG to that of carbon dioxide. In the UK an official set of GWPs for reporting purposes is published by DEFRA based on interna-tional guidance produced by the IPCC (Table 2.3).
The GWP assesses the effects of various GHG emissions relative to those of an equivalent mass of CO2 over a set time period, normally 100 years. Thus, methane has 21 times the global warming effect of CO2 over 100 years and sulphur hexafluoride almost 24,000 times.
Carbon dioxide accounts for by far the largest proportion (approxi-mately 85 per cent) of GHGs in the atmosphere, which is why there is so much attention focused on this particular gas. Although DEFRA now recommends expressing gases in terms of CO2e, CO2 emissions are some-times converted into carbon emissions. One tonne of carbon is contained in 3.67 tonnes of CO2. Other GHGs are frequently expressed in terms of carbon equivalent by multiplying their emissions by their GWP and then dividing by 3.67 (DEFRA, 2006).
At a global level, the movement of freight accounts for roughly a third of all the energy consumed by transport (UN IPCC, 2007). In the UK in 2004, transport accounted for 23 per cent of total energy-related CO2 emissions, with freight transport responsible for around 8 per cent (McKinnon, 2007) or 33.7 million tonnes of CO2. Road transport accounted for 92 per cent of this total, split in the ratio 86:14 between HGVs and vans. Rail and waterborne transport together represented
table 2.3 The global warming potential (GWP) of the six Kyoto greenhouse gases
greenhouse gas global Warming
Potential (gWP) DefrA
global Warming Potential (gWP) iPCC
Carbon dioxide (CO2) 1 1
Methane (CH4) 21 25
Nitrous oxide (N2O) 310 298
Hydrofluorocarbons (HFCs) 140–11,700 124–14,800 Perfluorocarbons (PFCs) 6,500–9,200 7,390–12,200 Sulphur hexafluoride (SF6) 23,900 22,800 Source: DEFRA (2008).
just under 8 per cent of freight-related CO2 emissions, with domestic air freight producing a negligible proportion.
Regional effects of atmospheric pollution
Airborne pollutants can diffuse widely from their original source, partic-ularly when carried by the prevailing winds. The two main examples of air pollution extending over extensive areas are:
Acid rain. This is caused by the emission of sulphur dioxide and
•
nitrogen oxides into the atmosphere. It interferes with the growth of flora and fauna and with water-life. Mainly as a result of the adoption of low and ultra-low-sulphur diesel in the trucking sector and, to a lesser extent, by rail freight companies, land-based freight transport is now responsible for a very small proportion of acid rain. The high sulphur content of the bunker fuels used in shipping presents a much more serious environmental problem, particularly around ports, although the International Maritime Organization (IMO) has imple-mented new regulations under Annex 6 of its MARPOL convention to radically reduce SOx emissions (IMO, 2008).
Photochemical smog. Photochemical smog is caused by the reaction of
• sunlight with nitrogen dioxide, especially during periods of still, settled weather (ie high pressure). It can extend over whole urban regions. Such smog can cause loss of lung efficiency and is thought to exacerbate asthma problems.
Local effects of atmospheric pollution
These effects are experienced in the immediate vicinity of the pollution source, where the concentration levels are high.
Nitrogen oxides (NOx). Nitric oxide and nitrogen oxide result from
• combustion at high temperatures where nitrogen and oxygen combine.
Short-term effects are rarely noticed but long-term exposure to fairly low levels can affect the functioning of the lungs. At higher levels, emphysema may occur (EPA, 2008).
Hydrocarbons (HCs). Hydrocarbons result from the incomplete
• combustion of organic materials. Included within this category are volatile organic compounds (VOCs). Many hydrocarbons, such as benzene, are known to be carcinogenic, though the actual levels likely to cause damage are not known precisely (US Dept of Health and Human Services, 1999).
Ozone (O
• 3). Ozone is formed when nitrogen oxides and VOCs react with sunlight. Exposure to high levels of ground level ozone can lead to respiratory problems and nausea. Children, asthmatics and the elderly may be more susceptible or vulnerable to the effects (Royal Society, 2008).
Particulates. Particulates come in various sizes and from a variety of
• sources. In the case of vehicles, the majority take the form of soot emitted by diesel engines, particularly those that are badly tuned.
There are concerns over the likely carcinogenic effects, particularly of the smaller PM10 particles (EPA, 2009). These particles are also linked to respiratory and cardiovascular problems and to asthma. It has been estimated that in the UK, PM10 pollution causes the premature deaths of 12,000–24,000 people annually and adds £9.1bn–£21bn to the national health budget (Rogers, 2007).
Carbon monoxide (CO). Carbon monoxide results from the
incom-• plete combustion of carbon-based fuels. It binds well with haemo-globin, which carries oxygen around the body. It binds 200 times more easily than oxygen and so reduces the circulation of oxygen. At low levels of exposure, perception and thought are impaired but at high levels it can cause death (HPA, 2009).
Sulphur dioxide (SO
• 2). Fossil fuels, particularly diesel, contain sulphur.
When they are burned in the engine, the remaining sulphur is converted into sulphur dioxide, an acidic gas which is then emitted through the exhaust pipe. Normally, it causes irritation to the eyes, nose and throat of those exposed to it. At low levels it may also tempo-rarily make breathing difficult for people with predisposed respi-ratory illness, such as asthma (HPA, 2008).
Noise pollution
Road traffic is the main cause of environmental noise at the local level.
The immediate adverse effects of noise disturbance include annoyance, communication difficulties, loss of sleep and impaired cognitive func-tioning resulting in loss of work productivity; longer-term, physiological and psychological health issues may also arise (den Boer and Schroten, 2007). Currently, around 30 per cent of the European Union’s population is exposed to road traffic noise and 10 per cent to rail noise levels above 55 dB(A). Data on aircraft noise exposure is less reliable, though it is thought that around 10 per cent of the EU population may be highly disturbed by air transport noise (EEA, 2003).
In the UK 90 per cent of people hear road traffic noise while at home and 10 per cent of these regard this noise source as highly annoying (Watts et al, 2006).
Trucks generate road noise from three sources:
propulsion noise (power train/engine sources), which dominates at
• low speeds (less than 50kmph);
tyre/road-contact noise, which is the main cause of noise at speeds
•
above 50kmph;
aerodynamic noise, which increases as the vehicle accelerates.
•
European vehicle noise standards for individual vehicles were intro-duced in the early 1970s (Directive 70/157/EEC), when the permitted noise emissions for trucks were set at 80 dB(A). Noise standards have been tightened several times since then (Affenzeller and Rust, 2005). Significant reductions in noise levels have been achieved by technical advances in engine design, tyres and the aerodynamic profiling of vehicles. Nevertheless, overall noise levels have not improved, as the growth and spread of traffic in space and time has largely offset both technological improvements and other abatement measures (INFRAS, 2004)
The European Union in 2001 launched regulations that limited the levels of noise generated by vehicle tyres (Directive 2001/43/EC). Tyre noise was targeted specifically for two reasons. First, tyre rolling noise is generally the main source of noise from trucks at medium and high speeds (see Sandberg and Ejsmont, 2002); and second, as tyres are replaced more frequently than vehicles, implementing tyre noise standards was considered to be one of the fastest ways to achieve road noise reductions.
In addition to quietening the vehicle, it is possible to cut noise levels by altering the acoustic properties of the road surface. FEHRL (2006) outline a range of noise-abatement measures that can be applied in the design and construction of road infrastructure.
As in road transport, technological improvements in air transport (from engine improvements and airframe design) have substantially reduced the noise of individual aircraft, but these performance improvements have been eroded by the growth of air traffic (Janić, 2007).
Accidents
Accidents cause personal injury and death for those involved, and general inconvenience for other road users. Overall, accidents involving HGVs by distance travelled are fewer than for cars, although there is a higher likelihood of an HGV being involved in a fatal accident, as shown in Table 2.4. This is partly a reflection of HGVs greater momentum, and partly due to the relatively high proportion of time that they are driven on faster roads.
The accident rate in the EU varies enormously, as shown in Table 2.5.
The country recording the highest fatality rate in accidents involving HGVs (Poland) has over six times more fatalities per million population than the country with the lowest rate (Italy). This difference is likely to be caused by a variety of factors, including driver behaviour, age of vehicles, vehicle maintenance, road standards and the nature and enforcement of safety regulations. The figures are also distorted by international varia-tions in the statistical definition of a fatal traffic accident, which centres around the maximum length of time elapsing between the accident and the death. Table 2.5 also shows that in every country where comparable figures exist, the number of fatalities has dropped considerably over the period 1997–2006, in some cases more than halving.
In the EU14, 13 per cent of fatalities in accidents involving HGVs and 12 per cent involving LGVs (<3.5 tonnes gross weight) are in urban areas, much lower proportions than for cars and taxis (22 per cent). Although the number of LGVs has been increasing through time, the total annual number of fatalities in this category in the EU14 fell from 2,973 in 1997 to 2,511 in 2005 (ERSO, 2008).
EnvIronmEntAl stAndArds
Environmental standards can be divided into two types; those that are mandatory and those that more environmentally responsible companies meet voluntarily. The former type is mostly technical, while the latter type is often more management orientated.
table 2.4 Vehicle involvement rates by accident severity in the UK, 2007 (rate per 100 million vehicle-kms)
severity hgvs Cars
Killed 1.6 0.8
Killed or seriously injured 6.6 7.5
All 36 63
Source: Department for Transport (2008).