Environmental Noise Barriers 2nd edition Environmental Noise Barriers A guide to their acoustic and visual design Second edition Benz Kotzen and Colin English First edition published by E & FN Spon 1999 This edition published 2009 by Taylor & Francis 2 Park Square, Milton Park, Abingdon, Oxon OX144RN Simultaneously published in the USA and Canada by Taylor & Francis 270 Madison Avenue, New York, NY 10016, USA Taylor & Francis is an imprint of the Taylor & Francis Group, an informa business This edition published in the Taylor & Francis e-Library, 2009. To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk. © 1999, 2009 Benz Kotzen and Colin English All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. This publication presents material of a broad scope and applicability. Despitestringent efforts by all concerned in the publishing process, some typographical or editorial errors may occur, and readers are encouraged to bring these to our attention where they represent errors of substance. The publisher and author disclaim any liability, in whole or in part, arising from information contained in this publication. The reader is urged to consult with an appropriate licensed professional prior to taking any action or making any interpretation that is within the realm of a licensed professional practice. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data Kotzen, Benz. Environmental noise barriers: a guide to their acoustic and visual design / Benz Kotzen and Colin English. — 2nd ed. p. cm. Includes bibliographical references and index. 1. Noise barriers—Design and construction. 2. Traffic noise. I. English, C. E. (Colin E.) II. Title. TD893.6.T7K5852009 625.7(cid:118)9—dc22 2008032407 ISBN0-203-93138-6 Mastere-bookISBN ISBN10: 0–415–43708–3 (hbk) ISBN10: 0–203–93138–6 (ebook) ISBN13: 978–0–415–43708–0 (hbk) ISBN13: 978–0–203–93138–7 (ebook) Contents Preface to second edition ix Preface to first edition xiii Acknowledgements xvii Locations of photographs xix 1 Introduction 1 Background 1 Environmental noise barrier terminology 4 Noise is a landscape issue 6 Barrier use: a contrast in provision 9 References 14 2 Defining the need for barriers 15 Legislation and policy 15 Introduction 15 The Land Compensation Act, 1973 16 The Noise Insulation Regulations, 1975 16 The Highways Act, 1980 17 National Government policy 17 Local government policy 19 Alternative European approaches 20 The Noise Insulation (Railways and Other Guided Transport Systems) Regulations, 1996 21 European Union directives 22 Risk to health 23 Design process 24 Acoustic assessment 25 vi Contents Landscape decision-making process 26 Landscape assessment 26 Assessment of visual intrusion 27 DMRB Assessment, consultation and design process 30 Summary of mitigation design strategies 33 Taking design strategies further 35 References 38 3 Acoustic performance of barriers 41 Introduction 41 Barrier theory 41 Sound insulation 44 Barrier placement 45 Barrier length 46 Bunds versus screens 47 Dealing with reflections from barriers 48 Reflections from vehicles 49 Improving the acoustic performance of a screen 51 Introduction 51 Cantilevered barriers 52 Tunnels 52 Galleried barriers 52 Louvred covers 52 Sonic crystals 53 Diffracting-edge modifications 53 Noise leakage through gaps 58 Varying longitudinal profiles 60 Noise screening by vegetation 61 Acoustic performance testing 62 References 63 4 Barrier morphology and design 67 Anatomy of barriers – elements and characteristics 67 Top section and top edge 67 Middle section 73 Bottom section and bottom edge 75 Barrier façades 76 Ends 77 Vertical profile – angled, contoured and cantilevered barriers 80 Support structures, transitions and foundations 84 Fixings 97 Other considerations 98 Viewing at speed 98 Two-faced barriers 100 Barriers: vertical or horizontal landscape elements? 105 Repetition 105 Pattern 112 Contents vii Texture 112 Colour 114 Light and shade 120 Profiling 122 Materials and design 123 Choosing materials – visual neutrality and compatibility 129 Night-time barriers 134 References and endnotes 134 5 Types of barrier and barrier materials 135 Introduction 135 DMRB guidelines 136 Noise barrier types 140 Earth mounds 140 Earth mounds and planting 145 Timber barriers 148 Sheet-metal barriers 151 Concrete barriers 158 Brick barriers 164 Plastic, PVC and fibreglass barriers 164 Transparent barriers 164 Cantilevered barriers 174 Thatch barriers 177 Bio-barriers 178 Integrated barriers 186 Barrier materials on bridges 193 Barriers and solar panels 193 Tunnels 195 Escape routes 202 Planting and barriers 202 Barriers and sustainable materials 205 References and endnotes 207 6 Climbing plants and other plants for use on barriers 209 Introduction 209 Considerations for choosing plant species 209 Vertical planting and potentials 211 Select list of climbers for use in the UK 214 References 219 7 Engineering, safety, environmental and cost considerations 221 Introduction 221 Engineering considerations 221 Environmental considerations 223 Graffiti 227 Costs 230 References 231 viii Contents 8 Contemporary issues, developments and considerations 233 Introduction 233 Noise is an ecological issue 233 Introduction 233 Birds 234 Other species 236 The potential for environmental noise barriers to enhance biodiversity 236 Environmental noise barriers and energy production 237 Photovoltaic barriers 237 Environmental noise barriers and air pollution production 240 Introduction 240 References 246 Author Index 251 Subject Index 253 Preface to second edition Undertaking the research for this second edition has allowed us to revisit many of those people whose help and advice proved so valuable when writ- ing the first edition. Travelling to see new barriers inevitably took us past old friends and allowed us to see how well these structures had stood the test of time. Once again we were struck by the wide discrepancy of provision from country to country. European countries such as the Netherlands, Switzerland, Austria and Italy continue to build substantial barriers to enhance the living conditions of their populations living near major roads, while, further afield, Australia is also creating some impressive barriers. Curiously, it is not always the poorer countries that fail to invest in good barriers to achieve acceptable environments, and for some unknown reason some countries simply lack the political will to invest in noise mitigation on behalf of their people. Our travels allowed us to view many of those barriers that had made the greatest impression on us a decade ago. These continue to work well acousti- cally, but we were surprised to see how dated the more elaborate designs looked after ten years’ service. It was often the simpler designs which appeared to fit into the current landscape better. Sadly, the ravages of time and graffitists have all too often taken their toll and this reinforced our opinion that, as with any built structure, barriers need occasional cleaning and maintenance. Planting is still considered important in barrier integration and is still one of the best ways of deterring graffiti. As before, it is the Netherlands that leads the way in barrier development and innovation. For many years air quality and noise have both been seen as environmental impacts of major roads and it was exciting to see that impor- tant work is being undertaken in the Netherlands to design noise barriers that can reduce the air pollution caused by the road traffic. In the past a few barriers have been designed with additions to exploit solar energy. This ten- tative exploration for amalgamating barrier design with photovoltaics has seen a sea change in the design of the 1,200 metre long 620 kilowatt