HA 66/95 - Standards for Highways

1 February 2001 DESIGN MANUAL FOR ROADS AND BRIDGESVOLUME 10 ENVIRONMENTALDESIGN ANDMANAGEMENTSECTION 5 ENVIRONMENTALBARRIERSPART 2HA 66/95 environmental barriers :TECHNICAL REQUIREMENTSSUMMARYThis Advice Note accompanies HA 65/94 ( ) and gives guidance on acoustic performance,forms of construction and physical properties FOR existing title page, content page andGeneral Preface page on the Goods Roads Guideseries of Advice new title this sheet as : A new contents page for Volume 10 datedSeptember 1995 is available with HA 75 66/95 environmental barriers :Technical RequirementsDESIGN MANUAL FOR ROADS AND BRIDGESTHE Highways AGENCYTHE SCOTTISH EXECUTIVE DEVELOPMENTDEPARTMENTTHE NATIONAL ASSEMBLY FOR WALESCYNULLIAD CENEDLAETHOL CYMRUTHE DEPARTMENT FOR REGIONAL DEVELOPMENT*Summary:This Advice Note accompanies HA 65/94 (DMRB ) and gives guidanceon acoustic performance, forms of construction and physical properties ofmaterials.

2 * A Government Department in Northern IrelandVolume 10 Section 5 Part 2 HA 66/95 September 1995 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsVolume 10 Section 5 Part 2 HA 66/95 September 1995 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsENVIRONMENTAL BARRIERSTECHNICAL REQUIREMENTSS eptember 1995 Volume 10 Section 5 Part 2 HA 66/95 Contents0/15.

3 EARTH MOUNDS AND RETAINING STRUCTURESE arthmounds and LandscapingEarth Retaining StructuresTechnical Approval6. ACOUSTIC SCREEN DESIGNG eneralWind and aerodynamic LoadingVehicle ImpactSupports and FoundationsDynamic Loads from Snow ClearanceVertical LoadsPropriety Barrier Systems7. MATERIALSM aterials Covered by SHWS pecification of AlternativesStructural PlasticsRecycled MaterialsTransparent MaterialsAirborne Sound InsulationSound Absorbent Materials1. INTRODUCTIONG eneralScopeImplementation2. NOISE FUNDAMENTALSG eneration and PropagationShielding and ReflectionDiffraction and Scattering3. NOISE CALCULATIONSP rediction MethodsPorous SurfacingNoise PropagationScreening by BarriersNoise ReflectionsWide Carriageways4.

4 BARRIER EFFICIENCYB arrier Cross SectionReflection and AbsorptionDispersion and ScatteringSeptember 1995 Volume 10 Section 5 Part 2 ha 66 /958. MAINTENANCED esign LifeVandalism and Fire RiskMaterials and Design DetailsCleaningOther Maintenance TasksAccess9. COST COMPARISONSI ntroductionInstallation Cost IndexMaintenance Cost Index10. SUPPLEMENT - NOISE AND TRAFFICD efinitionMeasurementRoad Traffic NoiseAtmospheric ConditionsTraffic Noise Spectrum11. REFERENCESAPPENDIX AWind Loading Design MethodAPPENDIX BSteel Sections for PostsAPPENDIX CMass Concrete Post FoundationsContents0/2 September 1995 Volume 10 Section 5 Part 2 ha 66 document provides general guidance on the criteriaused in designing environmental barriers .

5 The OverseeingOrganisations requirements for approval on the grounds of structuralintegrity are contained in BD 2/94: Technical Approval of HighwayStructures - Part 1: General Procedures (DMRB ). The particularfeatures required of contractor designed environmental barriers onindividual schemes are set out in Appendix 3/2 of the procurement of environmental barriers will normallybe carried out under contracts incorporating OverseeingOrganisations Specification for Highway Works (MCHW 1). Productsconforming to equivalent Standards and specifications of other statesof the European Economic Area and tests undertaken in other statesof the European Economic Area will be acceptable in accordancewith the terms of clauses 104 and 105 of MCHW 1.

6 For contractsnot incorporating this form of specification, advice should be soughton suitable clauses of mutual recognition which would have the document should be read in conjunction with HA 65(DMRB ) Design Guide for environmental barriers . It supportsthe overall advice given in the Design Guide with guidance onacoustic performance, forms of construction and physical propertiesof materials and supersedes H14/76: Noise barriers - Standards andMaterials (DMRB ). essentials of noise propagation and attenuation aresummarised and the basis of standard noise calculations areexplained, covering the effect of barriers in particular.

7 The relativeeffectiveness of different forms of barrier are discussed andreferences provided to permit further reading. environmental barriersin the form of thin panel constructions are given particular attentionunder the general heading of acoustic later chapters in this document describe the materialsand construction techniques which can be used in environmentalbarriers. Basic engineering requirements for the design of differentstructural forms are given with reference to the appropriatedocuments. A design method is provided for acoustic screens,together with a review of current information on a range of materialswhich may be used in their construction.

8 Indicators of relative costs,including those of maintenance, are given for various forms ofenvironmental 1995 Volume 10 Section 5 Part 2 ha 66 FUNDAMENTALSV ehicle and Traffic level of noise received at some distance from thesource is affected by a number of factors relating firstly to the amountof noise generated and secondly to the amount by which it isattenuated as it travels through the air. These effects are brieflysummarised here but covered in more detail in Chapter noise arises in different ways from the engine,transmission, bodywork, suspensions and tyres.

9 The most significantfactors affecting the noise are the engine speed and the speed onthe road. The dominant source of noise from vehicles cruising inhigh gear often arises from the interaction of tyres on the roadsurface, but the engine noise of heavy vehicles can be significant,especially when they are going up noise generated by large numbers of vehicles passinga continuous stream merges together and can be characterised bya representative level of noise at a given distance from the road (forexample 10 metres from the edge of carriageway). The noise leveldepends principally on the total flow of traffic, its average speedand the proportion of heavy vehicles, but may be modified by differentroad the purpose of assessment, the source of noise fromtraffic on a trunk road or motorway is normally taken as a line from the near edge of the carriageway and metres aboveit.

10 Allowance is made for various factors which affect the noisereaching a distant receiver. The factors affecting propagation are:i)Distance - starting from any reference point, the noise levelat another point which is twice as far from the line source will beapproximately 3dB(A) less because of the dispersion of )Soft Ground - The simple reduction with distance assumesthat sound either travels through free space or passes over a hardreflecting surface. If sound passes over a more absorbent form ofsurface such as grassland, it will be attenuated more )Angle of View - The treatment of traffic noise as a linesource assumes that it stretches to infinity in either direction.