Noise
TAG Unit 3.3.2

November 2006

Unit 3.3.2 (206kb)

Contents

Note

1. Noise

1.1 Introduction
1.2 Community response to transport noise
1.3 Annoyance response relationship
1.4 Monetary valuation of noise
1.5 Methodology for plans
1.6 Methodology for strategies
1.7 Quiet areas

2. Application of TAG to Highway Schemes

3. Further Information

4. References

5. Document provenance

Note

NOTE: The Department will expect ALL schemes submitted for funding after the 1 January 2007 to be consistent with this new guidance.

1. Noise

1.1 Introduction

1.1.1 Noise annoyance is defined by the World Health Organisation (WHO) as 'a feeling of displeasure evoked by noise'. The UK has well established procedures for assessing the nuisance to people caused by road and rail traffic-related noise and vibration. These procedures have been developed from surveys of the impacts of noise from transport on people, including dissatisfaction, annoyance and disturbance. More recently the Department for Transport commissioned a research study aimed at putting a monetary value on the impact of noise. This guidance document incorporates those monetary values in to its existing noise assessment. The inclusion of monetary valuation will enable decision-makers to assess the relative importance of noise impacts of a transport option in relation to other impacts currently measured in monetary terms.

1.1.2 Assessing the noise implications of multi-modal transport plans and strategies presents a particular challenge for two main reasons:

• People exhibit different responses to noise from and within different transport modes, making the determination of cumulative impact difficult; and
• Noise is a local impact which depends on the precise geometric relationship of source and receiver - while these will be easily ascertainable at the plan level of assessment, it is unlikely they will be sufficiently well defined at the strategic level.

1.1.3 Research studies both in the UK and other countries in Europe are attempting to address these difficulties. Much of this work has been initiated following the European Commission's green paper in 1996 on Future Noise Policy. The Commission's own work on the relationship between community annoyance and noise exposure levels will be useful in seeking a European consensus.

1.1.4 This TAG Unit provides guidance on how to assess the noise impacts of surface transport sources i.e. road and rail^[1]. The assessment involves two steps. The first, based on the concept of noise annoyance, involves calculating the difference in the estimated population who would be annoyed by noise from alternative sources, comparing the 'with scheme' and 'without scheme' scenarios^[2]. The second is based on the effect of noise on house prices and involves calculating the present value of households' willingness to pay to avoid transport related noise over the whole appraisal period for each scenario, the TAG Noise Spreadsheet automates this calculation. This automation now requires the cross-tabulation of households experiencing different noise level bands between the without scheme and with scheme scenarios. Estimates of both these effects can be based on relatively precise data at the plan level; whilst indications at the strategic level will be comparatively broad-brush.

(1) The Department has separately commissioned research into the attitudes to aircraft noise. It is intended that findings from this research will be integrated into this TAG unit in due course.

(2) The 'with scheme' term is being used in place of what was referred to as the 'do-something' scenario. The 'without scheme' term is being used in place of what was referred to as the 'do-minimum' scenario.

1.1.5 It should be recognised that, in many situations, relatively large changes in traffic flows are required to bring about significant changes in the response to noise levels in the longer term. For freely flowing traffic, a difference of about 3dB in noise level is required before there is a statistically significant change in the average assessment of nuisance. The assessment of nuisance however could still be affected even if there is only a 1dB change in the noise level if the change is associated with changes in the view of traffic, or if the change occurs suddenly. When options of this nature are being appraised, particularly strategies, the analyst will need to exercise judgement about whether the impact on noise should be ignored. Furthermore, care is needed in assessing options which may result in adverse noise impacts during the night. Whilst traffic levels and their resultant noise impacts are lower at night than during the day - by about 10dB on roads - people tend to be more sensitive to night-time noise. As noise during the night (midnight to 6am) is not covered in the 18 hour measures used for assessing the annoyance impacts and monetary values of noise, any significant changes in night-time noise should be reported in the qualitative assessment column of the Appraisal Summary Table (AST).

1.2 Community response to transport

1.2.1 Although individuals vary widely in their response to the same level of noise, even when it arises from the same source, the average or community response from a large number of people exposed to the same source of noise is relatively stable and a community average degree of annoyance can be associated with long-term average noise exposure. The concept of annoyance is generally recognised as a robust and well-established measure for identifying the long term noise impacts from roads and railways. However as stated, the same level of noise emitted by different sources provokes different responses, when measured as community annoyance.

1.2.2 One approach to overcoming this problem is to apply different impact criteria to each mode. This allows estimates of numbers of people exposed to different noise levels to be made on each mode. However in comparing the noise impact of each mode there is a residual problem in weighing up the significance of the impact against the number of people exposed. This problem is also encountered in single mode assessments, in that it is difficult to compare an option which has a small noise impact for a large population with an option which has a large noise impact for a small population, although the willingness-to-pay and annoyance-response approaches below offer ways of overcoming this.

1.3 Annoyance response relationship

1.3.1 The annoyance response relationship can be used when comparing the noise impacts of different road types as it estimates the numbers of people likely to be annoyed for each option. The relationship shows the percentage of a population annoyed^[3] by road traffic noise in the longer term as a function of the noise level. The latter is measured in L_{A10, 18 hr} as set out in the Calculation of Road Traffic Noise (DoT, 1988). As the basis of the relationship is long term, it ignores the immediate impacts of any change. DMRB 11.3.7 presents the relationship in tabular and graphical form.

(3) DMRB uses the phrase 'bothered very much or quite a lot'.

1.3.2 Road noise will need to be adjusted from L_{A10, 18 hr} to L_{Aeq, 18 hr} in order to associate noise levels with the monetary values that are based on L_{Aeq, 18 hr} levels. The conversion of L_{Aeq, 18hr} = L_{A10, 18hr} - 2.5 dB(A) should be applied to all L_A10 data calculated for the DMRB noise assessment before using the TAG Noise Spreadsheet which calculates both changes in annoyance and money values of noise changes from L_Aeq levels.

1.3.3 Railway noise levels are already calculated in L_{Aeq, 18 hr} (see Calculation of Railway Noise, DoT, 1995). There is no standard annoyance response relationship for railway noise but one has been developed for the purposes of this guidance.

1.3.4 Even when noise levels are measured using the L_{Aeq, 18 hr} scale, research indicates people respond differently to the same level of road and rail noise. For example, the Mitchell Committee's report Railway Noise and the Insulation of Dwellings (DoT, 1991) summarises research undertaken up to 1991 on the question of the differential between road and rail noise annoyance response. Although the Committee found no clear consensus, they concluded that at levels of 60 to 70dB(A) most studies found the same degree of annoyance where rail noise exceeded road traffic noise by between 4 and 9dB(A); but for noise levels of 50 to 60dB(A) the differential was very small or zero. In reaching their conclusion on the appropriate criterion for insulation against rail noise, the Committee gave emphasis to UK studies, as it was recognised that social and cultural factors might have a strong influence on the differential response.

1.3.5 Based on the results of this and other research, an annoyance response curve for rail traffic noise has been derived for use in this guidance. The differential between road and rail noise for equal annoyance has been taken as varying between:

• 0 at 55dB L_{Aeq, 18hr}; and
• 6dB at 70dB L_{Aeq, 18hr}.

1.3.6 The annoyance response relationship for road traffic noise was taken from DMRB 11.3.7, adjusted for noise measured in L_Aeq. The response for rail traffic noise was derived from this by applying the differential as above. The two relationships are given in Table 1.

1.3.7 The poorest performing option, in terms of noise, will be that with the largest increase in estimated population annoyed when comparing the with scheme scenario with the without scheme. However the current relationships are based on data gathered in past decades and further research is needed to assess the annoyance response to different sources of transport noise such as: i) high speed rail, which produces a significantly different spectrum of noise than conventional rail; ii) low frequency noise from light rail systems in urban areas; and iii) noise from road traffic which is not free flowing. This needs to be taken into account, and noted in the qualitative column of the AST, when assessing the noise impact of options which involve non-standard types of rail project or dealing with congested road traffic. Very little is also known about the combined effect of noise from different sources, as one source of noise can mask another.

1.3.8 It is also important to be aware that the annoyance response function is uncertain at low noise levels (especially over large distances). Consequently, it is recommended that appraisal is undertaken for noise above a cut-off level below which only a small percentage of the population would be annoyed. Previously a 55dB L_{Aeq,18 hr} cut-off had been used on the basis that the onset of community noise impact in the daytime was around this noise level. Recent research however suggests a positive willingness to pay to avoid transport related noise down to 45dB L_{Aeq,18 hr}, and as such this level is now used as the cut-off for both annoyance and valuation calculations.

1.3.9 Annoyance response functions and monetary valuations of noise are provided for noise levels up to 81dB L_{Aeq,18 hr}. Although noise levels in excess of this may be experienced road- or track-side, it is unlikely that adjacent properties will be affected by such high noise levels. In the rare case where noise levels exceed the upper limit, the highest monetary values and annoyance rates should be used and a comment should be included in the qualitative column in the AST.

1.3.10 For the appraisal process the assessment of noise impacts from multi-modal plans and strategies will compare the change in estimated population annoyed in the longer term for each option in relation to a without scheme scenario. The assessment should be carried out for fifteen years after the opening of the scheme. The degree of uncertainty in the calculation will depend on the quality and amount of detailed information available, including that for population distribution. It may be necessary to make simplifying assumptions to arrive at estimates of the change in population annoyed for each option. However, the approximate nature of these estimates need not invalidate comparisons between options.

Table 1: Annoyance Response Relationships for Road and Rail Traffic Noise

1.4 Monetary valuation of noise

1.4.1 As stated above, monetary valuation is intended to complement the existing noise assessment. It will be used to aid decision-makers when appraising different transport options and raise awareness of the environmental impacts of transport schemes such as noise. Noise valuation should, in general, always be undertaken at the plan stage which includes Local Transport Plans as well as fully-developed road and rail schemes. For strategies, it is understood that data requirements^[4] may make it infeasible to undertake noise valuation, however, if approximate data on the number of households or people affected by specific noise changes is available then valuation should be attempted for each option and a note made in the qualitative column of the AST regarding the approximation.

(4) Section 3 of the Supplementary Guidance has more information regarding data requirements.

1.4.2 The zero value placed on the impact of noise below 45dB L_Aeq reflects the finding of the DfT research which showed that below this level the monetary values people placed on noise could not be shown to be different from zero at a 95% confidence level. Similarly the research did not provide evidence on values of the impact of noise above 81dB L_Aeq, we assume the monetary value placed on a decibel change in noise remains constant above this. The data on the influence of railway noise on property prices did not provide sufficient evidence to make a distinction between road and rail for the monetary values of noise changes comparable with the differences in annoyance. Table 2 below shows the annual value of the impact of a 1dB change in exposure to noise at noise levels from 45 to 81 dB L_{Aeq, 18 hr}.

1.4.3 Table 2 below shows the annual value of the impact of a 1dB change in exposure to noise at noise levels from 45 to 81 dB LAeq, 18 hr. These are the standard appraisal values based on the UK average household income, for general use^[5]. They are expressed at 2002 prices and values and are assumed to grow in line with real GDP per household. They should be used with a positive sign to value the benefit of noise reductions and with a negative sign to value the disbenefit of noise increases.

⁽⁵⁾ Some specific cases may require using higher- or lower-income localities, in these cases please use the method outlined in Section 4.6 of the Supplementary Guidance.

Table 2: Monetary valuation of changes in noise level (per household, 2002 prices)

1.5 Methodology for plans

1.5.1 At the plan level, where options involve specific interventions, it is likely that a spatially detailed transport model will be available. The output from this type of model will enable an understanding to be gained of differences in road traffic flows on a link by link basis, which in turn will allow differences in noise for specific communities to be predicted. At this level, a detailed understanding of rail movements is also likely to be available.

1.5.2 Both changes in noise annoyance and the monetary value of the change in noise levels can be calculated using the TAG Noise spreadsheet, and Worksheet 1 can be used to aid data calculation for this. The following method describes the input data required for the TAG Spreadsheet and an overview of the methodology assumed within this.

1.5.3 Having generated data on road and rail traffic flows, the following four steps are required to calculate the noise impacts of different options. The results should be recorded in Worksheet 1 and the TAG Noise Spreadsheet. The appraiser will also need to specify the opening year of the scheme, the current year of appraisal and whether the scheme is a road or rail scheme. The latter will affect the annoyance levels only. For monetary valuation, noise data is required for both the without scheme and with scheme scenarios in the opening year and 15 years after the opening of the scheme. For annoyance levels only the data for 15 years after the opening of the scheme will be used.

(i) Noise levels: the noise spreadsheet requires noise data to be in 3dB(A) bands^[6]. These bands are <45, 45-47.9, 48-50.9, 51-53.9, 54-56.9, 57-59.9, 60-62.9, 63-65.9, 66-68.9, 69-71.9, 72-74.9, 75-77.9, 78-80.9,and >81dB in terms of L_{Aeq 18hr}. The numbers of residential properties within noise bands in 3dB(A) increments along transport alignments should be assessed using simplified standard prediction methodologies, such as the Calculation of Road Traffic Noise and the Calculation of Railway Noise. Noise levels are required for the without scheme scenario and the with scheme scenarios for each transport option in order to reveal the change in noise faced at each residential property. Noise levels should be estimated for all residential properties within 600m of the transport infrastructure concerned in the scheme e.g. a road. More detailed data on properties within 300m and on properties further away from this can provide more accurate estimates of noise levels in given situations. Many factors, such as the type of ground cover, the presence and degree of screening, wind direction and strength, can all influence noise levels and the extent of the noise footprint. Professional judgement is needed to assess the significance of specific factors and to determine which can be disregarded.

⁽⁶⁾ For noise data in other band widths see Section 3 of the Supplementary Guidance.

(ii) For noise annoyance, populations within these noise bands should be estimated. In the TAG Noise Spreadsheet this is calculated automatically once the user inputs an estimate of average household size. Explicit assumptions may need to be made about population densities in order to estimate population exposure, although census data and, where available, building occupancy databases and other sources can also be used. In the absence of more refined information the national average of 2.36 people per household (2001 Census) can be used. (This is the default used in the TAG Noise spreadsheet).

(iii) The annoyance functions and monetary values of changes in noise are presented above. The monetary values are national average values per household per year at 2002 prices. These are increased in line with forecasts of GDP per household and discounted over the appraisal period to give a present value of noise. More details on the process of applying monetary values for noise and the assumptions built into the TAG Noise Spreadsheet can be found in the Supplementary Guidance.

(iv) The incremental impact of each option, expressed in terms of differences in population annoyed, can be derived by subtracting, for each noise band, the population annoyed in the without scheme scenario from the population annoyed in the with scheme scenario and summing over all noise contours. Both this and the present value of the change in noise are automatic outputs of the TAG Noise spreadsheet, but can also be calculated separately for other years or noise profiles.

1.5.4 Care is needed where there appears to be the potential for double counting populations exposed to multiple sources of transport noise. As noted above, little is known about annoyance from multiple sources and expert judgement is important in these situations. In some cases, 'double counting' could give the best answer. For example, those disturbed by railway noise may be different from those who would be disturbed by road traffic noise, or, where noise sources are transient in nature, noise from one source might 'fill the gaps' in the varying noise levels arising from another. Furthermore, multiple sources may impact different facades of exposed buildings. For example, a road might affect the front of a property, while a railway line might be to the rear of the same property. Even if the facade noise levels generated by the two sources were similar, there is no reason to assume that the annoyance caused would be identical.

1.5.5 Where the levels of noise from different sources are dissimilar, it may be reasonable to make a simplifying assumption and ignore annoyance from the source giving lower annoyance. However, where there is uncertainty, it is more difficult to make such a simplifying assumption and professional judgement will be needed to reduce the risk of double counting populations.

1.5.6 It is possible that the resident population in the affected properties or the number of properties in the study area will change over time but as a general rule appraisers should assume a constant number of households over time. However, where there are grounds to confidently predict changes in the affected number of households it would be appropriate to reflect this in the number of households exposed to transport noise in the forecast year. Further information is available in Section 4 of the Supplementary Guidance, which also discusses the methodology to be used if, in the forecast year, the number of households changes between the with scheme and without scheme scenarios.

Quantitative column

1.5.7 The entries in the quantitative column of the AST should show the estimated numbers of people who are likely to be annoyed in the longer term in the without scheme scenario and the with scheme scenario in the fifteenth year.

Overall assessment score

1.5.8 The entry in the Overall Assessment column should show:

(i) The net difference in the estimated population who are likely to be annoyed in the longer term as a result of the option compared to the without scheme scenario in the fifteenth year;

(ii) The estimated present value of the change in noise (at 2002 prices) discounted over the 60 year appraisal period.

These are both calculated as outputs from the TAG Noise Spreadsheet.

Qualitative comment

1.5.9 A qualitative entry in the AST should be used to highlight any factors which cannot be readily understood from the numbers in the Quantitative and Overall Assessment columns. For example, there may be a significant impact on night time noise, or instances of properties experiencing noise levels in excess of 80dB L_{Aeq 18hr}. For noise insulation issues the number of properties experiencing noise levels above 68dB L_{Aeq 18hr} in the with scheme scenario should be highlighted. Also the appraiser may wish to comment on whether noise impacts on potentially noise sensitive non-residential receptors (for example schools or hospitals) both nearer and further than 600m band from the road/railway are likely to be significant. An indication can be given of the main factors causing any change in noise conditions.

1.6 Methodology for strategies

1.6.1 For strategies, if the data required for plans is available, this can be used to generate monetary values and annoyance levels as above. However, at the strategic level, it is envisaged that options will generally be assessed using a spatially coarse transport model, given that they are reasonably informative and comparatively quick to run. Spatially coarse models will be likely to provide only a broad indication of changes in transport behaviour arising from strategy options, expressed in such terms as changes in passenger car unit kilometres or vehicle kilometres across a model zone or regional study area. Such model output does not enable noise impacts to be identified at specific receptor sites. Consequently, a more broad-brush, two step assessment must be undertaken, based on determining the change in average noise emission and relating this to population data, rather than predicting the expected noise levels. One of the difficulties associated with estimating effects at this level is that the dose response relationship between noise and annoyance is non-linear. In order to estimate average effects the method recommends that these relationships should be linearised. However the analyst should be aware that this may have implications for the range of noise levels which can be assessed with any degree of confidence. The results should be recorded using the TAG Noise spreadsheet and Worksheet 2 provided at the end of this TAG Unit. As the monetary value of noise impacts depends heavily on the initial levels of noise, monetary valuation is not meaningful for strategies in the absence of this information at a reasonable level of detail.

Step 1

1.6.2 The first stage involves using transport model outputs to estimate the difference in noise emissions between the without scheme and with scheme scenarios for hypothetical sections of the road and rail network within model zones. Average noise emission indicators, such as those in the Calculation of Road Traffic Noise and Calculation of Railway Noise (Basic Noise Level) should be used. For example, for road options, data on zonal flows (vehicle kilometres), speed and traffic composition from a strategic transport model can be used to estimate changes in average zonal noise emission levels in each of the model's zones. When assessing changes in noise under different scenarios, it may not be manageable to predict absolute noise levels over large areas, but it will generally be possible to predict the relative difference between the various options. Provided that total traffic flow, traffic composition (e.g. % heavy goods vehicles for roads and freight movements for rail) and traffic speed are used to calculate the noise emission levels, the method should give realistic comparisons between options. Factors such as road surface, distance to receiver and screening effects can be ignored because they will not vary between options. The entries in the quantitative column of the AST should show the estimated numbers of people who are likely to be annoyed in the longer term in the without scheme scenario and the with scheme scenario in the fifteenth year.

Step 2

1.6.3 Comparing options on the strength of the change in zonal noise emission levels alone should be avoided, as it makes no allowance for population distribution and therefore actual noise impacts, which are receptor dependent. For example, an option that moves traffic from local roads to motorways may show increased average noise emission levels because it enables greater traffic speeds. However it may result in a lower total noise impact because motorways tend to be more distant from large communities.

1.6.4 The change in average noise emission levels, between the without scheme and with scheme scenarios, should be related to population data, to enable the change in the estimated population annoyed to be determined. Spatially coarse transport models (and/or their GIS adjuncts) will generally hold data on population levels across model zones. The following steps should be followed:

(i) The length of the transport network within each modal zone, in km, should be multiplied by the width of the impact corridors in metres, to estimate the magnitude of the noise impact (in terms of area) for each zone, within the study area.

(ii) For each zone the area impacted - expressed in km² - should be multiplied by the zonal population densities to derive estimates of the population exposed.

(iii) An estimate of the difference in population annoyed by noise in each zone can be derived by multiplying the estimate of the population exposed by the percentage of the population annoyed by the change in the average noise emission level.

(iv) These estimates by zone can then be summed to arrive at an indicator of estimated change in population annoyed across the whole study area, for each option.

1.6.5 In determining the area of noise impact, assumptions will need to be made about the areas adjacent to transport links which are likely to be affected. For roads, an appropriate distance should be taken for the first band of properties, say 50m for urban/suburban schemes and then further bands of 100m, 200m, up to maximum corridor width of 400m should be considered, with an attenuation rate of 3dB(A) per band applied. However, this may not be appropriate in all cases and other assumptions may need to be made. For rail, more so than for roads, the area of impact will depend more on local conditions. Rail tends to involve much more variation in horizontal and vertical alignment than roads, which will have a bearing on noise levels and, therefore, the appropriate swathe distance to adopt. Broad assumptions will need to be made about the overall length of the rail network in tunnels, cuttings etc. This may be different for each multi modal study area and it is important that these assumptions are made explicit. For rural schemes there may be justification for increasing the corridor width. Professional judgement is needed to determine the distance of the impacts.

1.6.6 In determining the change in the percentage of the population annoyed, it should be noted that predictions of average noise emission levels, based on outputs from strategic transport models, will often tend to over estimate the actual levels of noise. Where the average noise emission is predicted to be over 65dB L_{Aeq, 18 hr} the change in the percentage of the population annoyed should, based on table 1, be assumed to be 3% per dB for road and 2% per dB for rail.

1.6.7 Population densities within zones may vary, particularly between rural and urban zones. In some cases, this may lead to inaccuracies in the estimated population annoyed, which should be noted on Worksheet 2. However the approach is conceptually similar to that applied at the plan level and does identify the benefits or otherwise (in terms of noise impacts on people in buildings) arising from changes in traffic across these zones. The main difference at the strategic level is that vehicle kilometres by zone are used instead of traffic flow data on road/rail links and zonal population densities replace geographic population data.

1.6.8 Worksheet 2 has a row for each study zone and for some studies with numerous zones it may be very large. Therefore in these cases it may be useful to summarise separately the information on Worksheet 2 and show the numbers of zones where population annoyance is increased, decreased or unchanged, as well as the total change in population annoyance over the whole study area.

1.6.9 The change in population for all the zones should also be shown in a graphical or mapped format, depending on the size of the study. For example, for a 20 zone study a simple bar chart showing the change in community annoyance in each zone may give a clear picture of the benefits and disbenefits of the strategy option. The results of a more complex regional study may be more clearly shown on maps using colour-coded ranges of change in population annoyance for each zone.

Quantitative column

1.6.10 The entries in the Quantitative column should show the estimated numbers of people in the area who are likely to be annoyed in the fifteenth year after opening in the without scheme scenario and the with scheme scenario. As with plans, appraisers should also comment where significant impacts are likely to affect important non-residential receptors e.g. school and hospitals as well as where night time noise levels (not included in the 18 hour measures of noise) are disproportionately affected.

Overall assessment score

1.6.11 The entry in the Overall Assessment column should show the net difference in the estimated population who are likely to be annoyed in the longer term as a result of the option compared to the without scheme scenario in the fifteenth year.

Qualitative comment

1.6.12 A qualitative entry in the AST should be used to highlight any factors which cannot be readily understood from the numbers in the Quantitative and Overall Assessment columns. An indication can be given whether there is an overall improvement or worsening of conditions as a result of an option compared to the without scheme and the main factors causing any change in conditions.

1.7 Quiet areas

1.7.1 In general, noise assessment from transport is limited to the consideration of effects on people in occupied buildings, so-called noise sensitive receivers (dwellings, schools, hospitals etc). The debate on noise impacts stimulated by developing EC noise policy has raised concern about other spaces, particularly those used for recreation, that currently enjoy a peaceful environment, referred to as 'quiet areas'. Some Member States have become concerned that attempts to improve the noise climate in areas of high exposure may lead to a spreading of noise across areas that are currently almost free from transportation noise. There is a perceived need to protect these quiet or tranquil areas.

1.7.2 However, 'tranquillity' is one of the features defining landscape, and changes in tranquillity will be taken into account in the assessment of impact under the landscape sub-objective. Thus, in order to avoid double counting, the noise impacts of plans and strategies in quiet or tranquil areas should not be assessed under the noise sub-objective.

2. Application of TAG to Highway Schemes

This section provides advice on the links between TAG's treatment of the noise sub-objective and the advice given in Volume 11 of the Design Manual for Roads and Bridges (DMRB), which deals with the environmental assessment of highway projects. An explanation of the correspondence between the advice set out in TAG and DMRB is given in Applying the multi-modal new approach to appraisal to highway schemes, TAG Unit 2.6.

The existing noise assessment advice within the DMRB is currently being revised. The Highways Agency has stated that this revision, which has an expected publication date of late 2007, will incorporate guidance to ensure outputs are compatible with this TAG Unit.

2.1 Methods and Worksheets

2.1.1 TAG requires similar base calculated data on noise levels, noise level changes and people annoyed by noise to that output from the DMRB 11.3.7 Stage 3 assessment, but the noise level data is expressed in terms of L_{Aeq, 18hr}. The TAG Noise spreadsheet shows the information that should be reported for this sub-objective. The AST should contain the outputs of the TAG Noise Spreadsheet, i.e. the absolute numbers of people annoyed in year 15 of the scheme, the change in people annoyed and the present value of the change in noise. The completed spreadsheet should then be submitted for reference.

• TAG Noise Spreadsheet (MS Excel - 182kb)

• Worksheet 1 (MS Word - 44kb)

• Worksheet 2 (MS Word - 54kb)

• Supplementary Guidance (MS Word - 419kb)

2.2 Data Transformation from DMRB to TAG

2.2.1 Calculated noise levels can be taken direct from the DMRB assessment, and converted to L_{Aeq, 18hr} plus a further analysis for the without scheme scenario in future. TAG requires noise levels for the opening year of the scheme and a future year of 15 years after scheme opening in the without scheme and with scheme scenarios.

2.2.2 In TAG, the comparison is between the without scheme and the with scheme scenarios in the future year, 15 years after opening. There are differences in the basic parameters of assessment used by DMRB and TAG, which require some transformation of the outputs from DMRB.

2.2.3 TAG requires an estimate of the population exposed to noise levels in defined noise bands, based on 3dB(A) and 5dB(A) interval noise contours. DMRB 11.3.7 on the other hand uses an estimate of the number of properties exposed to noise levels and changes. The DMRB property data can be converted to population numbers by assuming an average household size. This should be taken from either population census data for the study area or the national average household size of 2.36 (Census 2001).

2.2.4 TAG requires noise levels in the future year without scheme and with scheme scenarios to be grouped into bands: <45, 45-47.9, 48-50.9, 51-53.9, 54-56.9, 57-59.9, 60-62.9, 63-65.9, 66-68.9, 69-71.9, 72-74.9, 75-77.9, 78-80.9 and >81dB(A) and these can be derived from the DMRB results, adjusted to L_{Aeq, 18hr}, and entered into the TAG Noise Spreadsheet.

2.2.5 Nuisance or Annoyance - TAG requires an estimate of the number of people annoyed by noise in the longer term in the without scheme and with scheme scenarios, based on the population exposed to different noise levels (L_{Aeq, 18hr}, in 3dB interval bands) multiplied by the Annoyance Response Function (expressed as % highly bothered by noise) given in Table 1 above. This uses the relationship given in DMRB 11.3.7 Figure 2 which assesses the current nuisance. However, DMRB assesses the change in nuisance level in the without scheme and with scheme scenarios compared to the current situation expressed as number of properties where the change in percentage bothered (taken from Figure 3) is grouped: <10%, 10<20%, 20<30%, 30<40%, ≥40%. In this case it is not possible to use the DMRB results; a new assessment will be required for TAG.

2.2.6 Annoyance - TAG uses 'estimated population likely to be annoyed by noise in the longer term' as an indicator of noise effects and calculates the net difference in population likely to be annoyed by noise between the with scheme and without scheme scenarios in the 15th year. This indicator was principally selected for TAG as a way of overcoming the difficulty of combining the effects of noise from different sources of transport. By using 'annoyance', it is possible to assess the combined road, rail and air noise effects on the population. The TAG presentation is a simplification of the fuller environmental assessment results. For the purpose of the environmental assessment, the changes in annoyance in the short term must also be recorded.

2.2.7 Monetisation - TAG requires the initial level and change in household exposure to noise for the without scheme and with scheme scenarios in both the opening year of the scheme and 15 years after.

2.2.8 TAG highlights the need to protect quiet or tranquil areas. This is dealt with under the Landscape sub-objective and is not assessed under Noise. If the quantitative assessment does not properly represent the adverse effects on tranquil areas then a comment should be made in the qualitative column.

2.3 DMRB Stages 1 and 2 / TAG

2.3.1 At DMRB Stages 1 and 2 no noise calculations are made, only an estimate of the number of properties within 300m of existing and new routes, except where sensitive locations are identified. Therefore, only a simple TAG appraisal can be achieved at these early stages such as the number of properties within distance bands.

2.3.2 Where there is more information available, however, a simple quantification of annoyance should be attempted.

3. Further Information

The following documents provide information that follows on directly from the key topics covered in this TAG Unit.

4. References

Bateman, I.J., Day, B.H., & Lake, I. (2004), The Valuation of Transport-Related Noise in Birmingham, DfT. (Available at: www.dft.gov.uk/pgr/economics/rdg/birmingham/).

British Medical Association (1997), Road Transport and Health.

Department of Transport (DoT) (1991), Railway Noise and Insulation of Dwellings, Report of the Mitchell Committee, HMSO.

Department of Transport (DoT) (1988), Calculation of Road Traffic Noise, DoT, Welsh Office, HMSO.

Department of Transport (DoT) (1995), Calculation of Railway Noise, HMSO.

Department of the Environment, Transport and the Regions (DETR), Design Manual for Roads and Bridges, Environmental Assessment, Volume 11, London, The Stationary Office.

Department of Health (1988), Our Healthier Nation: a contract for health, CM 3854, The Stationary Office.

Fletcher, T and McMichael, AJ (1997), Health at the crossroads, Transport policy and urban health, Wiley, Chichester.

Hillman, Boyd, Tuxworth (1999), Promoting Cycling as a Way to a Healthier Life - Proceedings from Velo City 1999, Graz, Austria (11th International Bicycle Planning Conference).

Health Education Authority (1998), Transport and Health: A Brief for Health Professional and Local Authorities.

L M Pearce (TRL), AL Davies (Adrian Davis Associates), Dr HD Crombie (Independent Consultant) and HN Boyd (Allot and Lomax), Cycling for a Healthier Nation, TRL Report 346.

Nellthorp, J., Bristow, A., & Mackie, P., (2005) Developing Guidance on the Valuation of Transport-Related Noise for Inclusion in WebTAG, DfT. (Available at: www.dft.gov.uk/pgr/economics/rdg/birmingham/guidanceonthevaluationoftran3049).

Parker, DM (1995), English Nature Science Series No 21.

Transport Research Laboratory (1999), An examination of the noise index L_{Aeq, T} and review of traffic noise prediction models, Unpublished.

5. Document Provenance

This Transport Analysis Guidance (TAG) Unit is based on Chapters 4, Section 3 (including worksheets 4.1 and 4.2) of Guidance on the Methodology for Multi-Modal Studies Volume 2 (DETR, 2000); together with Section 7.1 of Applying the Multi-Modal New Approach to Appraisal to Highway Schemes ("The Bridging Document") (DETR, 2001).

Technical queries and comments on this Unit should be referred to:

Integrated Transport Economics and Appraisal
Department for Transport
Zone 3/08, Great Minster House
76 Marsham Street
London SW1P 4DR

E-mail: itea@dft.gsi.gov.uk
Tel: 020 7944 6176
Fax: 020 7944 2198