Lecture #9 Environmental Aspects

8/10/2019 Lecture #9 Environmental Aspects

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H22 IS3 : Transport Infrastructure

Topic #9 :

Environmental Aspects


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Introduction Environmental aspects

Noise Vibration Air quality Visual impact Congestion Intimidation Severance

Physical Damage Ecological impact Water Quality and Drainage

Summary


Contents


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Introduction

The broad spectrum of environmental considerations has onlyrelatively recently impinged significantly on the life of thehighway engineer.

In the past, it was sufficient for the highway designer to ensurethat a certain amount of grass was seeded on the verges,

cuttings & embankments of road schemes to maintain a greenlook, but many of the wider aspects were overlooked. The impetus for a greater awareness of the environment has

come about in response to public demand, following publicityabout the rate at which environmental destruction hasproceeded over the past few decades.

The increasing volume of road traffic has also become veryobvious to all.



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Introduction

The European Community took the initiative with a directive in1988 & this was implemented in the UK shortly afterwards.

The Department of Transport issued a Manual forEnvironmental Assessment , which has been the basis for theway in which the highway engineer takes account of the

environment ever since. The following paragraphs introduce most of the different

aspects of the environment which now have to be carefullyconsidered before a road scheme can go ahead.



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Air Quality

Engines produce: Co, Pb, hydrocarbones, No2 High concentrations accumulate in enclosed spaces


Visual Impact

Fences, walls & cuttings can hide roads The main enhancers of visual impact are trees and shrubs Colouring of footway/shoulders


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Congestion

Particularly important where pedestrians are involved Traffic congestion leads to noise, air pollution, danger, nuisance

to motorists In this context parking needs very careful consideration Footways, cycleways & roads all compete for the same limited

space and it is the responsibility of highway planners to takethe hard decisions as to which is given preference in aparticular circumstance.



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Intimidation

Closeness between pedestrians & road vehicles meansintimidation

Kerbs are important in reducing this effect Pedestrianisation is an ideal which is appropriate in some urban

situations

Traffic calming has become a big growth area



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Severance

Roads can divide communities, so adequate safe crossing pointsmust be provided



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Ecological Impact

Since 1949 the UK has lost: 95% of lowland meadows 80% of lowland limestone grasslands 40% of lowland heaths 30-50% of ancient woods 50-60% of fens

Roads have not been responsible for most of this but theyrepresent one of the major continuing threats; such areas shouldwhere possible be avoided

Bridges and tunnels can be considered rather than large

embankments or cuttings Animal tunnels under roads can work for some species Landscaping should be carried out using native local species;

topsoil, which is commonly used to initiate growth, is suitable forgrasses only

Roads can actually create protected habitats along their verges



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Water Quality and Drainage

Highway drainage has to be able to cope with chemical spillswithout allowing damaging materials into the drinking watersupplies

Streams, marshes etc are very sensitive to the effects of highwaydrainage; without careful planning, erosion, drying up of ponds,pollution can all occur ; with planning new habitats can actually be

created.



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Summary

That the environment is important very few would argue against.The problem is just how important is it in relation to thecomparatively short term benefits which the public derives from anefficient road network?

Unfortunately, it is never possible to measure the true cost ofenvironmental damage in terms of money alone.

For this reason, it will never be possible to allow the ordinarycitizen (or company) a free hand in carrying out projects whichhave an impact on the environment and legislation is the only wayof ensuring that sensible measures and precautions are taken.

However, legislation in this area is not easy and inevitably givesrise to interpretations & opinions, & subsequent heated arguments.

Meanwhile the responsibility of the engineer is to make sensibledecisions, making the best possible balance between all the usuallyconflicting demands which are made by various parties.


The End of Topic #9

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Lecture #9 Environmental Aspects