Highways Agency

• 1. Introduction
• 2. Existing Conditions
• 3. Scheme Proposals
• 4. Engineering Assessment
• 5. Environmental Assessment - 1
• 5. Environmental Assessment - 2
• 5. Environmental Assessment - 3
• 5. Environmental Assessment -4
• 5. Environmental Assessment - 5
• 5. Environmental Assessment - 6
• 5. Environmental Assessment -7
• 5. Environmental Assessment -8
• 5. Environmental Assessment -9
• 5. Environmental Assessment -10
• 5. Environmental Assessment -11
• 5. Environmental Assessment -12
• 5. Environmental Assessment -13
• 5. Environmental Assessment -14
• 5. Environmental Assessment -15
• 5. Environmental Assessment -16
• 5. Environmental Assessment -17
• 5. Environmental Assessment -18
• 5. Environmental Assessment -19
• 6. Traffic and Economic Assessment

5. Environmental Assessment -8

5. Environmental Assessment (continued)

5.8 Air Quality and Greenhouse Gases

5.8.1 Introduction

This section details the Stage 2 air quality assessment for the proposed A14improvements between Ellington and Fen Ditton, Cambridgeshire.

Vehicle exhausts contain a number of pollutants including carbon dioxide (CO₂),carbon monoxide (CO), hydrocarbons, oxides of nitrogen (NO_x) and particles. Thequantity of each pollutant emitted depends upon the type and quantity of fuel used,engine size, speed of the vehicle and abatement equipment fitted. Once emitted,the pollutants disperse in the air. Pollutant concentrations in the air can bemeasured or modelled and then compared with ambient air quality criteria.

5.8.2 Air Quality Criteria and Pollutants

Air quality criteria can be readily divided into two groups; those that are mandatoryand those that are designed for guidance. Mandatory criteria that apply to the UKare the objectives from the Air Quality Strategy for the UK and the EuropeanCommunity Directive limit values, which are incorporated into regulations. The airquality criteria used in this assessment are given in Table 5.15.

It should be noted that whilst the current annual mean AQS objective for PM₁₀ is40µg/m³, with 35 exceedances of the 24-hour mean AQS objective, a morestringent objective of 20µg/m³, with 7 exceedances of the 24-hour mean is to beapplied in 2010, although currently these objectives are provisional and notincluded in Regulations.

AIR POLLUTANTS

Nitrogen Dioxide (NO2)

Nitrogen dioxide is a secondary pollutant produced by the oxidation of nitric oxide(NO). Nitric oxide and nitrogen dioxide are collectively termed nitrogen oxides(NO_x). Approximately half of the UK NO_x emissions are from road transport. Themajority of NOx emitted from vehicles is in the form of nitric oxide, which oxidisesrapidly in the presence of ozone to form nitrogen dioxide. In high concentrations,nitrogen dioxide can affect the respiratory system.

Particulate Matter

Particulate matter in vehicle exhaust gases consists of carbon nuclei onto which awide range of compounds are absorbed. These particles are less than 10 µm indiameter. Particles with a median diameter of less than 10 µm are referred to asPM₁₀. Diesel engines produce the majority of particulate emissions from thevehicle fleet. About a quarter of primary PM₁₀ emissions in the UK are derived fromroad transport. Particulate matter appears to be associated with a range ofsymptoms of ill health including effects on the respiratory and cardiovascularsystems, on asthma and on mortality.

Carbon Monoxide (CO)

The majority of carbon monoxide emitted in the UK is from motor vehicles. It isreadily absorbed through the lungs and reduces the oxygen carrying capability ofthe blood.

Hydrocarbons

The term 'hydrocarbons' is used to include all organic compounds emitted fromvehicles both in the exhaust and by evaporation from the fuel system, and coversmany hundreds of different compounds. About one third of the UK hydrocarbonemissions are produced by road transport. Hydrocarbons are important precursorsof photochemical smog and oxidising compounds. The DMRB requires anassessment for benzene and 1, 3-butadiene as these are included in the Air QualityStrategy. They are both genotoxic carcinogens and exposure to them isassociated with certain types of leukaemia.

Carbon Dioxide

Carbon dioxide is a major product of the combustion of carbon containingmaterials. Carbon dioxide does not affect human health at ambient levels and so isnot significant as a local pollutant but is important for its national and internationalrole in climate change. About 20% of the UK carbon dioxide emissions areproduced by road transport.

5.8.3 Existing Conditions

LOCAL AIR QUALITY REVIEW AND ASSESSMENT

All local authorities are required by Part IV of the Environment Act 1995 to reviewair quality in their area and to assess present and likely future air quality against setobjectives.

If an area is identified as being unlikely to achieve the Air Quality Strategy (AQS)objectives, the local authority is required to designate an Air Quality ManagementArea (AQMA) and develop an action plan to improve air quality.

The following local authorities contain roads with a significant change in traffic(±10%) with the proposed improvements and/or a section of the existing or newalignment of the A14:

• Cambridge City Council
• Huntingdonshire District Council
• South Cambridge District Council

A partnership of five local authorities in and around Cambridgeshire, includingthose listed above, was set up to carry out the review and assessment of air qualityin Cambridgeshire. Following the completion of the first round of the review andassessment process none of the local authorities above have declared anyAQMAs.

As part of the second round of the review and assessment process local authoritiesmust complete an updating and screening assessment (USA) to identify mattersthat have changed since the first round of review and assessment and identifysources that may lead to an air quality objective being exceeded. A detailedassessment is required where there is a possibility of AQS objectives beingexceeded.

Local authorities in Cambridgeshire produced their USA in 2003. Cambridge CityCouncil has proceeded to a detailed assessment for NO2 and is likely to declare anAQMA within the city centre. No other local authorities identified the requirementfor further work after completion of the USA. However, following completion of theAir Quality Review and Assessment Progress Report 2004, Huntingdon DistrictCouncil and South Cambridge District Council will be progressing to detailedassessments. Huntingdonshire will complete the detailed assessment for NO2 dueto likely exceedances in the vicinity of Huntingdon Ring road and associated feederroads. South Cambridge will produce a detailed assessment for NO2 around theA14 corridor east of Bar Hill, including Girton, Histon, Impington and aroundSawston High Street, and for PM₁₀ due to exceedances of the daily objective atImpington.

MONITORING

Measurements may be made of pollutant concentrations by deploying analyticalinstruments that measure continuously and record the average concentrations overspecified time intervals. Simpler sampling devices, such as diffusion tubes, adsorbpollutants over a longer time period and are subsequently analysed at a laboratoryto give an average concentration for the sampling period. National survey resultsfrom both types of monitoring are published in the UK National Air Quality InformationArchive¹, and the closestrelevant data are summarised below.

Continuous Monitoring

Defra operates a network of automated continuous monitoring sites throughout theUK. The closest sites in the network to the study area are Cambridge Roadside,Continuous monitoring is also undertaken by local authorities at locations given inTable 5.13.

Non-continuous Monitoring

Nitrogen dioxide can also be monitored passively using diffusion tubes. Localauthorities across the UK take part in Defra's nitrogen dioxide survey and alsocarry out their own monitoring surveys.

Data from the following Defra sites are considered here:

• Cambridge - 5 sites located approximately 3-4 km south of the A14 at Histon Junction;
• Histon - 5 sites located approximately 2 km north of the A14 at Histon Junction;
• Sawston - 2 sites located approximately 3 km east of the M11 between junctions 10 and 11/ 12km south of the A14 at Fen Ditton;
• St Neots - 5 sites located approximately 12 km south southeast of the A14 at Huntingdon.

Local authorities monitor NO2 with diffusion tubes at the following number of locations:

• Cambridge City Council - 42 locations;
• Huntingdonshire District Council - 22 locations;
• South Cambridgeshire District Council - 19 locations.

MONITORING SURVEY NEAR A14

Atkins commenced in a year long nitrogen dioxide monitoring programme usingdiffusion tubes in June 2004. Nineteen sites were selected, based on the expectedchanges in traffic flows on the network in the study area. Refer to theEnvironmental Assessment Report for details of and location of sites.

As recommended by Defra's Technical Guidance² three diffusion tubes were colocatedwith a continuous monitor (Cambridge Roadside site) to enable theaccuracy and precision of the tubes to be determined. Comparison of the meanconcentrations in each monitoring period gives a correction factor which can thenbe applied to the diffusion tubes at the other sites. The corrected results for thefirst three months of monitoring are shown in Table 5.14.

Concentrations are shown to exceed the annual mean AQS objective at Sites 14and 15, 5m and 10m from the edge of the A14 respectively. Concentrations at allother sites were below the AQS objective. A report will be issued followingcompletion of the monitoring survey.

SUMMARY

Concentrations of 1,3-butadiene, benzene and carbon monoxide are escaped toachieve their respective AQS objectives throughout the study area. There arenumerous exceedences of the annual mean NO2 objective, especially at roadsidesites, indicating that concentrations are likely to be sensitive to any changes intraffic flows. The hourly NO2 objective was exceeded at one site close to the A14in 2003. The annual mean PM₁₀ AQS objective was achieved, but the 24-hourobjective was exceeded at two sites close to the A14.

5.8.4 Methodology

APPROACH TO ASSESSMENT

The assessment was carried out in accordance with the Design Manual for Roadsand Bridges (DMRB) Volume 11 section 3, part 1, air quality, revision February2003 and Transport Analysis Guidance (TAG) The Local Air Quality Sub-objectiveUnit 3.3.3, February 2004. The scheme has been assessed in terms of:

• A constraints map showing areas within 200m of roads affected by the scheme options, which may experience changes in air quality;
• A Local Impact Assessment comprising estimated pollutant concentrations at selected properties in relation to the relevant criteria;
• An assessment of the overall change in exposure to concentrations of NO2 and PM₁₀ following guidance in the DfT's TAG, the TAG Assessment

CONSTRAINTS MAP

Constraints maps were drawn to show areas within 200m of the roads affected bythe proposed improvements that are likely to have a change in air quality. Thisallows identification of the number of properties where people are likely to besubjected to a change in air quality, the identification of sensitive properties andproperties likely to experience higher than average pollutant concentrations atlocations such as road junctions. Sensitive properties include those where theremay be vulnerable occupants, such as schools, hospitals or homes for the elderly.Table 5.14 displays the type and number of sensitive properties identified within200m of the A14 and affected roads.

LOCAL AIR QUALITY IMPACT ASSESSMENT

The DMRB screening method was used to estimate concentrations of carbonmonoxide, nitrogen dioxide, benzene, 1,3-butadiene and particulate matter (PM₁₀)to compare with AQS objectives. Predictions were made both with and without theproposed A14 improvements, termed the scheme and do-minimum respectively.The years selected for assessment were the existing case (2003), and the openingyear (2010).

Amended Options

A total of 12 amended route options were assessed, due to the variouscombinations of the traffic options and route and junction alignments.

The assessment was carried out assuming the traffic forecasts for two schemeoptions, OXF and PY6 and a Do Minimum (DM8). The traffic options wereassigned to the appropriate route options. These were each compared with the DoMinimum situation.

Table 5.17 sets out the basic junction, route and traffic forecast options that arebroadly headed as 'Blue', 'Orange' and 'Purple' and combined Blue/Orange andPurple/Orange scenarios.

Limited Junction Options

A total of 7 limited junction options were assessed, due to the various combinationsof the traffic option and route and junction alignments.

The assessment was carried out assuming the traffic forecasts for one option, EA9and the Do Minimum used for the amended options (DM8). The traffic option wasassigned to the appropriate route options and compared with the Do Minimumsituation.

Table 5.18 sets out the basic junction, route and traffic forecast options that arebroadly headed as 'Blue' and 'Orange' and combined Blue/Orange.

Limited Junction Options

A total of 7 limited junction options were assessed, due to the various combinationsof the traffic option and route and junction alignments.

The assessment was carried out assuming the traffic forecasts for one option, EA9and the Do Minimum used for the amended options (DM8). The traffic option wasassigned to the appropriate route options and compared with the Do Minimumsituation.

Table 5.18 sets out the basic junction, route and traffic forecast options that arebroadly headed as 'Blue' and 'Orange' and combined Blue/Orange.

For all alignment and traffic options the study area for the air quality assessmenthas been defined based on the change in traffic on the road network. Additionaltraffic is expected to be induced on the A14 and the pattern of traffic flow on theroad network will be affected by the increased capacity of this road.

A large number of road links are within the study area. DfT's TAG states "optionswhich change traffic flows by less than 10% can usually be scoped out, unless theroad is a motorway or there are particular sensitivities". On this basis the networkfor the air quality assessment included all existing and new alignments of the A14,and all other roads with flows of greater than 5,000 vehicles per day whichexperience an increase or decrease in traffic of greater than 10% with any of thetraffic options.

The road network assessed for each traffic option in this study area is illustrated inthe air quality constraints maps.

Receptor Selection

Usually, a number of specific properties or receptors are chosen for assessment.However, for this assessment, as the study area under consideration was so large,Ordnance Survey Address-Point® data was used to pinpoint the location ofresidential properties. For each property, the Address-Point® dataset contains aunique identifier, national grid reference and postal address. When identifyingproperties from maps without address point data, accidental consideration ofstructures not used for occupancy by people can occur. Using Address-Point® dataensures only buildings with a postal address are included in the count. The dataalso contains a field for business name which is used to screen the data to removebusiness addresses.

The use of an access database enabled the air quality at all properties within 200mof the scheme and affected roads to be calculated. In addition to residentialproperties, the effect on air quality at schools and other sensitive properties within200m of affected roads can be assessed. Concentrations at properties near thejunctions on the A14 were calculated using the DMRB spreadsheet rather than thedatabase, due to the complexity of the junctions.

Comparison of Modelled and Monitored Concentrations

To provide some validation of the concentrations predicted using the DMRB, acomparison of estimated and measured concentrations was undertaken for NO2and PM₁₀ at the location of continuous monitoring stations close to the A14.The DMRB screening method was used to calculate concentrations at the localauthority continuous monitoring sites at Bar Hill, Godmanchester and Impington.

TAG ASSESSMENT

This assessment gives a quantitative indication of whether the scheme would leadto an overall improvement or deterioration in air quality at properties and is basedon the DfT's Transport Analysis Guidance (TAG) The Local Air Quality Sub-Objective Unit 3.3.1, February 2004.

The method involves estimating concentrations of NO2 and PM₁₀ using the DMRBscreening method described above. The calculations were carried out with andwithout the proposed scheme for the opening year (2010).

Pollutant concentrations decrease with increasing distance from the traffic,therefore concentrations are calculated at 20 m, 70 m, 115 m and 175 m from theroad centre, with and without the proposed scheme, for each route option.

The number of properties in 50 m bands from the centre of each road link wascounted out to a distance of 200 m for the do minimum and scheme scenarios.The Address-Point® dataset, described above, and a geographic informationsystem was used to facilitate this. The number of properties in each band ismultiplied by the concentration calculated for that band for the do minimum andscheme scenarios. This is carried out for each of the four bands and the resultsadded together to give a total for each scenario. The do-minimum value isdeducted from the scheme value for each affected route. The overall assessmentscore is calculating by summing values over all routes, with an improvement(decrease in concentrations) having a negative value and a deterioration (increasein concentrations) having a positive value.

5.8.5 Results

LOCAL AIR QUALITY IMPACT ASSESSMENT

Pollutant concentrations at properties within 200m of the existing and newalignments of A14 and other roads affected by a significant change in traffic due tothe scheme have been calculated. This area includes some 65000 properties.

Due to the large number of properties assessed, it has not been possible to reportthe predicted concentrations at each property. Instead, the concentrations havebeen compared with the AQS objectives to determine whether any exceedanceshave been predicted.

Exceedances of AQS Objectives

Base Year (2003)

In 2003 the annual mean AQS objective for NO2 was estimated to be exceeded at21 properties. Located predominantly in Cambridge. For all other pollutants and atall other receptors the AQS objectives were achieved.

Amended Options and Limited Junction Options

In 2010 the AQS objectives for all pollutants are expected to be achieved at allreceptors for all traffic and alignment options. Some exceedances of theprovisional 2010 annual mean PM₁₀ objective were predicted in Cambridge.Approximately 30 properties are expected to exceed this provisional objective withthe Do-Minimum and limited junction options, and 20 properties with the enhancedjunction options.

Changes in Concentrations at Receptors

Table 5.19 and Table 5.20 give details of the maximum concentrations andgreatest changes predicted at receptors for nitrogen dioxide and PM₁₀ respectively.

There are expected to be both increases and decreases in concentrations atreceptors with all scheme options. There are around 70 properties with anincrease in annual mean NO2 concentrations of greater than 4µg/m³, and around90 properties with a decrease in annual mean NO2 concentrations of greater than4µg/m³. The greatest increases for NO2 with the scheme options are 5µg/m³, andthe greatest decreases between 11 and 16µg/m³.

For PM₁₀ no properties are expected to have an increase in annual meanconcentrations greater than 2µg/m³. Between 34 and 45 properties are expectedto have a decrease in annual mean PM₁₀ concentrations of greater than 2µg/m³.The greatest decreases with the scheme options are 6µg/m³.

Amended and Limited Junction Options

Annual mean concentrations of NO2 and PM₁₀ at the 14 receptors near junctions onthe proposed and existing alignments of the A14 for the amended and limitedjunction options are shown in the Environmental Assessment Report.

None of the receptors are expected to exceed any of the AQS objectives in anyyear or scenario. Many of the receptors are expected to have similarconcentrations with all of the scheme options, this is particularly the case for thosereceptors close to the common route alignments.

For NO2 the greatest increase at any receptor is 8.6 µg/m³ at Grafham RoadCottage. This is with O4a and BO4a, as the orange route passes close to thesereceptors.

Concentrations at Little Cottage, Brampton Lodge, Rectory Farm and Depden Farmare expected to have increases of 3.6, 2.8, 2.5 and 2.1 µg/m³ respectively.Increases at all other receptors are expected to be negligible.

The greatest decrease occurs at Hackers Fruit Farm, 9.1 µg/m³ with options B4a,B5a, B6a, O3a, O4a, B/O3a and B/O4a. This is as a result of the changes in roadalignment of the A14 near to this receptor. Little Cottage and Woodhatch Farm areexpected to have decreases of 5.4 and 5.1 µg/m³ respectively. These decreasesoccur with options P1a, and P/O1a due to changes in road alignment and trafficflows in proximity to these receptors.

The Hotel near Huntingdon Road Bar Hill, and the Public House at Trinity FootJunction are expected to have decreases of 2.8 and 1.4 µg/m³ respectively.Changes in concentrations at other receptors are expected to be negligible.

The changes in concentrations for PM₁₀ follow the same pattern as for nitrogendioxide. The greatest increases for PM₁₀ are at Grafham Road Cottage, LittleCottage and Depden Farm with increases of 2.4, 1.6, and 1.0 µg/m³ respectively.The greatest decreases are expected to occur at Hackers Fruit Farm, Little CottageWoodhatch Farm and Grafham Road Cottage with decreases of 2.1, 1.6, 1.4 and1.2 µg/m³ respectively. All other receptors are expected to have a negligiblechange.

Comparison of Modelled and Monitored Concentrations

The results of the comparison of modelled and monitored concentrations for 2003 are shown in Table 5.21.

The results indicated that in all cases there was an under prediction in modelledconcentrations of NO2 and PM₁₀ compared to the measured concentrations ofaround 30%. Average factors of 1.3 and 1.5 for NO2 and PM₁₀ respectively, werederived. Meteorological conditions in 2003 were largely responsible for poorer airquality in this year than in previous years, hence concentrations were alsoestimated for 2002 using the 2003 traffic data, and compared with the monitoringdata for 2002, shown in Table 5.22.

In 2002 there is still an under prediction in modelled concentrations of NO2 andPM₁₀ compared to the measured concentrations. However, at Godmanchester themodelled concentrations are more comparable. At Impington there is still an underprediction of around 30%, and at Bar Hill the under prediction is around 15-20%.Average factors of 1.2 and 1.1 for NO2 and PM₁₀ respectively, were derived. Whenreceptor concentrations in 2010 are multiplied by these factors there will still be noexceedances of annual mean AQS objective for either NO2 or PM₁₀.

However, with the 2003 adjustment factors, concentrations of nitrogen dioxide mayexceed the annual mean AQS objective at small number of receptors. The majorityof these receptors are located in Cambridge. However, there are some receptorslocated in the vicinity of the A14. These receptors are given in Table 5.23.

A nitrogen dioxide diffusion tube monitoring survey at locations near the A14 iscurrently underway which will provide further data for validation.

AMENDED AND LIMITED JUNCTION OPTIONS

The results of the assessment are summarised in Table 5.24 for PM₁₀ and Table 5.25 for nitrogen dioxide.

The assessment of the scheme options shows that there is an overall increase inPM₁₀ and NO2 concentrations at the properties near the A14 with all of the options.In the wider network, there is expected to be a large decrease overall in both PM₁₀and NO2 concentrations, which outweighs the increase near the A14.

The overall assessment shows that the scheme will lead to an improvement in bothPM₁₀ and NO2 concentrations at affected properties. For the enhanced Junctions,the purple and purple/orange routes have the lowest number of properties with animprovement and the highest number with a deterioration. The blue and orangeroutes have broadly similar results. For the limited junctions, there is littledifference between options.

A comparison of both of route options indicates that the amended options have thelargest number of properties with an improvement in air quality. The limitedjunction options have the least properties with an improvement in air quality, andthe least properties with a deterioration in air quality.

5.8.6 Conclusions

The stage 2 air quality assessment has consisted of examining existing conditions,assessing the change in concentrations at properties likely to be affected by theproposed scheme options, and undertaking an overall assessment of exposureaccording to the TAG methodology.

Measured concentrations of annual mean nitrogen dioxide are expected to exceedthe AQS objective near roadside sites in the study area, as well as near the A14.

Concentrations of PM₁₀ also exceeded the 24-hour mean objective at sites near theA14, although concentrations were below the annual mean objective.

Concentrations of carbon monoxide, benzene and 1,3-butadiene are all well belowtheir respective AQS objectives. Although there are no air quality managementareas in the study area at present, detailed assessments are currently in progress,and it is likely that an AQMA will be declared in Cambridge city centre, and aroundthe ring roadand associated feeder roads in Huntingdon.

The results of the local air quality assessment show that there are a small numberof exceedances of the provisional 2010 annual mean PM₁₀ AQS objective, with allscheme options and the do-minimum situations. None of the other AQS objectivesare expected to be exceeded in the opening year, based on raw modelling results.

There are expected to be both increases and decreases in concentrations atreceptors with all scheme options. There are around 70 properties with anincrease in annual mean nitrogen dioxide concentrations of greater than 4µg/m³,and around 90 properties with a decrease in annual mean nitrogen dioxideconcentrations of greater than 4µg/m³. The greatest increases for nitrogen dioxidewith the scheme options are 5µg/m³, and the greatest decreases between 11 and16µg/m³. For PM₁₀ no properties are expected to have an increase in annual meanconcentrations greater than 2µg/m³. Between 34 and 45 properties are expectedto have a decrease in annual mean PM₁₀ concentrations of greater than 2µg/m³.The greatest decreases with the scheme options are 6µg/m³.

A comparison of modelled and measured data has been undertaken for the threecontinuous monitoring sites near the A14. Concentrations were compared to datain 2003, and due to the high results experienced in this year, to data in 2002.Modelled concentrations in 2003 were shown to under estimate the measuredconcentrations at all three monitoring stations, by around 30%. Modelledconcentrations in 2002 were still shown to underestimate those measured at theBar Hill and Impington sites, although they were comparable at the Godmanchestersite for nitrogen dioxide. By applying adjustment factors derived from the 2002comparison, modelled concentrations are still expected to achieve the AQSobjectives, although with the 2003 adjustment factors, annual mean concentrationsof nitrogen dioxide may exceed at a small number of receptors. A monitoringsurvey at sites along the A14 is currently in progress which will further help validatethe results of the modelling.

The TAG assessment of the scheme options shows that there is an overallincrease in PM₁₀ and NO2 concentrations at the properties near the A14 with all ofthe options. In the wider network, there is expected to be a large decrease overallin both PM₁₀ and NO2 concentrations, which outweighs the increase near the A14.The purple and purple/orange routes have the lowest number of properties with animprovement and the highest number with a deterioration. For the blue and orangeroutes the results are broadly similar. Comparison of the 2 sets of route optionsindicates that the amended options have the largest number of properties with animprovement in air quality. The limited junction options have the least propertieswith an improvement in air quality, and the least number with a deterioration in airquality control.

1. http://www.airquality.co.uk back [1]
2. (Ref: Local Air Quality Management: Technical Guidance LAQM.TG(03), Defra, 2003) back [2]