Environmental impact of transport
The environmental impact of transport is significant because transport is a major user of energy, and burns most of the world's petroleum. This creates air pollution, including nitrous oxides and particulates, and is a significant contributor to global warming through emission of carbon dioxide. Within the transport sector, road transport is the largest contributor to global warming.
Environmental regulations in developed countries have reduced the individual vehicle's emission. However, this has been offset by an increase in the number of vehicles, and increased use of each vehicle. Some pathways to reduce the carbon emissions of road vehicles considerably have been studied. Energy use and emissions vary largely between modes, causing environmentalists to call for a transition from air and road to rail and human-powered transport, and increase transport electrification and energy efficiency.
The transportation sector is a major source of greenhouse gas emissions (GHGs) in the United States. An estimated 30 percent of national GHGs are directly attributable to transportation—and in some regions, the proportion is even higher. Transportation methods are the greatest contributing source of GHGs in the U.S., accounting for 47 percent of the net increase in total U.S. emissions since 1990.
Other environmental impacts of transport systems include traffic congestion and automobile-oriented urban sprawl, which can consume natural habitat and agricultural lands. By reducing transportation emissions globally, it is predicted that there will be significant positive effects on Earth's air quality, acid rain, smog and climate change.
The health impact of transport emissions is also of concern. A recent survey of the studies on the effect of traffic emissions on pregnancy outcomes has linked exposure to emissions to adverse effects on gestational duration and possibly also intrauterine growth.
As listed above direct impacts such as noise and carbon monoxide emissions create direct and harmful effects on the environment, along with indirect impacts. The indirect impacts are often of higher consequence which leads to the misconception that it’s the opposite since it is frequently understood that initial effects cause the most damage. For example, particulates which are the outcome of incomplete combustion done by an internal combustion engine, are not linked with respiratory and cardiovascular problems since they contribute to other factors not only to that specific condition. Even though the environmental impacts are usually listed individually there are also cumulative impacts. The synergetic consequences of transport activities. They take into account of the varied effects of direct and indirect impacts on an ecosystem. Climate change is the sum total impact of several natural and human-made factors. 15% of global CO2 emissions are attributed to the transport sector.
|Transport mean||Passengers |
Aviation emissions vary based on length of flight. For covering long distances, longer flights are a better investment of the high energy costs of take-off and landing than very short flights, yet by nature of their length inevitably use much more energy. CO2 emissions from air travel range from .24 kg CO2 per passenger mile (.15 kg/km per passenger) for short flights down to .18 kg CO2 per passenger mile (.11 kg/km per passenger) for long flights. Researchers have been raising concern about the globally increasing hypermobility of society, involving frequent and often long distance air travel and the resulting environmental and climate impacts. This threatens to overcome gains made in the efficiency of aircraft and their operations. Climate scientist Kevin Anderson raised concern about the growing effect of air transport on the climate in a paper and a presentation in 2008. He has pointed out that even at a reduced annual rate of increase in UK passenger air travel and with the government's targeted emissions reductions in other energy use sectors, by 2030 aviation would be causing 70% of the UK's allowable CO2 emissions.
Worse, aircraft emissions at stratospheric altitudes have a greater contribution to radiative forcing than do emissions at sea level, due to effects several greenhouses gases in the emissions, apart from CO2. The other GHGs include methane (CH4), NOx which leads to ozone [O3], and water vapor. Overall, in 2005 the radiative forcing caused by aviation amounted to 4.9% of all human-caused radiative forcing on Earth's heat balance.
Unleaded gasoline has 8.91 kg and diesel has 10.15 kg of CO2 per gallon. CO2 emissions originating from ethanol are disregarded by international agreements however so gasoline containing 10% ethanol would only be considered to produce 8.02 kg of CO2 per gallon. The average fuel economy for cars sold in the US 2005 was about 25.2 MPG giving around 0.35 kg of CO2 per mile. The Department of Transportation's MOBILE 6.2 model, used by regional governments to model air quality, uses a fleet average (all cars, old and new) of 20.3 mpg giving around 0.44 kg of CO2 per mile.
In Europe, the European Commission enforced that from 2015 all new cars registered shall not emit more than an average of 0.130 kg of CO2 per kilometer (kg CO2/km). The target is that by 2021 the average emissions for all new cars is 0.095 kg of CO2 per kilometre.
On average, inner city commuting buses emit 0.3 kg of CO2 per passenger mile (0.18 kg/km per passenger), and long distance (>20 mi, >32 km) bus trips emit 0.08 kg of CO2 per passenger mile (0.05 kg/km per passenger). Road and transportation conditions vary, so some carbon calculations add 10% to the total distance of the trip to account for potential traffic jams, detours, and pit-stops that may arise.
On average, commuter rail and subway trains emit 0.17 kg of CO2 per passenger mile (0.11 kg/km per passenger), and long distance (>20 mi, >32 km) trains emit 0.19 kg of CO2 per passenger mile (0.12 kg/km per passenger). Some carbon calculations add 10% to the total trip distance to account for detours, stop-overs, and other issues that may arise. Electric trains contributes relatively less to the pollution as pollution happens in the power plants which are lot more efficient than diesel driven engines.
The fleet emission average for delivery vans, trucks and big rigs is 10.17 kg CO2 per gallon of diesel consumed. Delivery vans and trucks average about 7.8 mpg (or 1.3 kg of CO2 per mile) while big rigs average about 5.3 mpg (or 1.92 kg of CO2 per mile).
Discharges of sewage into our water bodies can come from many sources, including wastewater treatment facilities, runoff from livestock operations, and vessels. These discharges have the potential to impair water quality, adversely affecting aquatic environments and increasing the risks to human health. While sewage discharges have potentially wide-ranging impacts on all aquatic environments, the impacts may be especially problematic in marinas, slow-moving rivers, lakes and other bodies of water with low flushing rates. Environmentally this creates invasive species that often drive other species to their extinction and cause harm to the environment and local businesses.
Emissions from ships have a much more significant environmental impacts; many ships go internationally from port to port and are not seen for weeks, contributing to air and water pollution on its voyage. Emission of greenhouse gases displaces the amount of gas that allows for UV-rays through the ozone. Sulfur and nitrogen compounds emitted from ship will oxidize in the atmosphere to form sulfate and nitrate. Emissions of nitrogen oxides, carbon monoxide, and volatile organic compounds (VOC) will lead to enhanced surface ozone formation and methane oxidation, depleting the ozone. The effect of the international ship emission on the distribution of chemical compounds like NOx, CO, O3, OH, SO2, HNO3, and sulfate is studied using a global chemical transport model (CTM), the Oslo CTM2. In particular, the large-scale distribution and diurnal variation of the oxidants and sulfur compounds are studied interactively. Meteorological data (winds, temperature, precipitation, clouds, etc.) used as input for the CTM calculations are provided by a weather prediction model.
|Mode of Transport||kg of CO2 per Ton-Mile|
The road haulage industry is contributing around 20% of the UK’s total carbon emissions a year, with only the energy industry having a larger impact, at around 39%. Road haulage is a significant consumer of fossil fuels and associated carbon emissions – HGV vehicles account for almost 20 percent of total emissions.
Mitigation of environmental impact
Road-Rail Parallel Layout
Road-Rail Parallel Layout is a design option to reduce the environmental impact of new transportation routes by locating railway tracks alongside a highway. In 1984 the Paris—Lyon high-speed rail route in France had about 14% parallel layout with the highway, and in 2002, 70% parallel layout was achieved with the Cologne–Frankfurt high-speed rail line.
When changing how we use the road systems and how they factor into the amount of pollution they contribute, using existing roads is key for changing the current layout of our road system. When deciding to construct mitigation work, steps should be taken to install permanent and temporary access roads as needed to support drilling/development and production phases of the project, but minimize the number and length of such roads. For drilling activities, using old or two-track road access rather than constructing a higher quality access road. Develop a traffic management plan for site access roads and for use of main public roads. Develop and implement measures to control off-highway vehicle traffic off of newly constructed access roads. Limit traffic to roads and portions of rights-of-way indicated specifically for the project. Instruct and require all personnel and contractors to adhere to speed limits to ensure safe and efficient traffic flow. Encourage project employees to carpool to work sites. Limit construction vehicle traffic on public roadways to off-peak commuting times to minimize impacts on local commuters. Restore roads to equal or better condition than before project construction after the heavy construction period is complete. Lastly, controlling dust along unsurfaced roads--especially near residences and farm fields--may help prevent mixture of plants that can lead to disputes over patents.
Mitigation does not entirely involve large-scale changes such as road construction, but everyday people can contribute. Walking, cycling trips, short or non-commute trips, can be an alternate mode of transportation when traveling short or even long distances. A multi-modal trip involving walking, a bus ride, and bicycling may be counted solely as a transit trip. Economic evaluations of transportation investments often ignore the true impacts of increased vehicular traffic—incremental parking, traffic accidents, and consumer costs—and the real benefits of alternative modes of transport. Most travel models do not account for the negative impacts of additional vehicular traffic that result from roadway capacity expansion and overestimate the economic benefits of urban highway projects. Transportation planning indicators, such as average traffic speeds, congestion delays, and roadway level of service, measure mobility rather than accessibility.
The environmental impact of transport in Australia is considerable. Australia subsidizes fossil fuel energy, keeping prices artificially low and raising greenhouse gas emissions due to the increased use of fossil fuels as a result of the subsidies. The Australian Energy Regulator and state agencies such as the New South Wales' Independent Pricing and Regulatory Tribunal set and regulate electricity prices, thereby lowering production and consumer cost.
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