The Environment

It has been shown that there is a clear interrelationship between the construction of a transportation system and its environment. The transportation infrastructure has a very strong effect on land uses throughout its useful life. However, for many years the environmental impact of a transportation project has been recognized as having much broader impacts than simply those on land use. The construction of a facility can bring about sweeping environmental changes in an area that reaches far beyond the immediate environs of the project. Malawi had generally neglected environmental issues from time of independence to mid 90s when environmental policy was developed that has affected transportation planning. The government of Malawi is changing from use of leaded petrol to unleaded petrol.

The transportation planner has to make an environment impact analysis. The transportation plan should consider environmental impact in the following areas:

1. Noise
2. Air pollution
3. Water pollution and run-off changes
4. Long- and short-term land use and socioeconomic changes

Noise Noise can be defined as unwanted sound that is a by-product of the operation of transportation vehicles. In the vicinity of highways and airports, noise pollution is a significant problem. Noise-sensitive environments, such as hospitals, schools, and residences, are forced to relocate in attempts to avoid this harmful side effect. Automobiles generate noise from such sources as the engine, the tyres and gearbox. Aircraft produce noise from their engines and from the aerodynamic flow of air over the fuselage and wings. Railroad trains also generate noise aerodynamically in addition to the noises generated by rail wheel contact and traction motor noises.

Figure 1.3 Sound levels dBA. (Source: Noise Pollution, US Environmental Protection Agency, Washington, D.C. 1972.)

The scale of the problem of noise generation is illustrated by figure 1.2 that sets noise levels of the transportation vehicles within the context of other everyday sounds. Loudness, which is the subjective magnitude of sound, is normally considered to double with an increase in sound intensity of 10dB. The ear is particularly sensitive to frequencies within the A-range. Therefore sound normally is measured using A-weighted decibels (dBA) which reflect these sensitive ranges. Physical pain is caused if the sound pressure level is 140 decibels or above.

Air Pollution -Air pollution is the contamination of the air by various particles and gases. All forms of transportation are associated with this contamination to some extent, but combustion engines on vehicles seem to emit the greatest amount of pollutants. The polluting effects of aircrafts, railroads, and water vessels are minimal but those of motor vehicles exceed three-quarters of transportation pollution.

The major components of air pollution due to transportation are:

Carbon monoxide: This is a principal by-product of the internal combustion engine of the automobile. It is produced in substantial quantities when the engine is idling or operating below normal cruise speeds. It is a poisonous gas that, even in low concentrations, can produce slow operating reactions, nausea, headaches, and dizziness. In large concentrations it can kill by reacting with blood hemoglobin.

Oxides of nitrogen: A by-product of combustion is the production of nitric and nitrogen dioxide. The latter is an irritant. This major component of smog causes very severe breathing problems at high concentrations.

Oxides of sulphur: Fuels containing sulphur form sulphur dioxide in the combustion process. When mixed with the normal water vapour chemical in the atmosphere it produces a highly irritant chemical that can cause severe discomfort to the eyes, nose and throat; in high concentration it can produce pulmonary disease. The pollutant is corrosive and can damage structures of steel and stone.

Hydrocarbons: Hydrocarbons are largely the result of poor combustion. They result from un burnt fuels in the exhaust and from leakage around the crankcase. In the atmosphere they undergo photochemical change to produce the highly oxidizing chemicals of smog.

Particulates: These highly visible products of poorly controlled combustion are mainly dust and carbon. The larger particles settle out of the air, finer material stays suspended and may form the basis of smog or fog. In themselves they are not toxic, but they may act to convey toxic pollutants to the lungs.

Water pollution and run-off changes In general the water pollution of transportation projects are small in comparison with the noise and air pollution implications. The exception can be airports where the vast paved areas can produce substantial increases in run-off into local streams. Equally, there may be local effects on aquifers and local ground water level changes.

Long- and short-term land use and socioeconomic changes The construction of transportation facilities can influence the long-term use of land in a variety of ways. These land use changes are of mixed benefit to the community and therefore generate mixed reactions from those affected. The following are a few of the many long-term changes that have been associated with major transportation projects:

• High-density corridor and station development following the construction of a rapid transit system.
• Disruption of existing community structure with the need to provide huge park-and-ride parking lots at rapid transit locations.
• Long-term ‘planning blight’ as areas become classified as transition areas awaiting redevelopment to more intense uses.
• The division of socially cohesive communities by right-of-way for freeways and rapid transit.
• Traffic ‘blight’ caused by substantial increases in moving and parked traffic with concomitant increases in noise fumes, fumes, and general discomfort.
• Economic segregation, caused by making suburban areas more accessible, with a consequential long-term abandonment of the urban centre by the wealthier income group sand the secular in-migration of lower income groups.

Even in the short-term there may be effects during the construction period that can have substantial effects on the existing land use and its occupants. These effects have been ignored too frequently in assessing the overall social costs associated with the project. They include:

• Relocation of residents and businesses on both a permanent and temporary
• The economic consequences of the disruption of the construction period on business and industry.
• The damage and disruption caused by construction traffic.