Implementing the CNOSSOS-EU correction near traffic light junc- tions and roundabouts Simon Shilton 1 Acustica Limited 3000 Aviator Way, Manchester, M22 5TG RafDouglas C. Tommasi 2 Tommasi and Tommasi Via Tavagnacco, 89, 33100 Udine, Italy

ABSTRACT Under the Environmental Noise Directive (END), the Round 4 strategic noise maps are to be calcu- lated using the methodology set out in Directive 2015/996 (as amended) (CNOSSOS-EU). As part of the road traffic source emission model, a correction for the effect on noise levels due to the acceler- ation and deceleration of vehicles shall be applied near crossings with traffic lights and roundabouts. As part of the revision of the EPA guidelines on strategic noise mapping in Ireland, a technical in- vestigation was carried out to identify the effect of the correction factor on road traffic noise emis- sions, and determine whether there was a practical approach to implement the correction factor within the upcoming noise mapping. This paper will provide an overview of the results, including the change in noise level emissions for low-speed low flow roads, and high-speed high flow road. It will also present a practical approach to preparing the road traffic flow models in GIS based on available datasets.

1. INTRODUCTION

The European Communities (Environmental Noise) Regulations [1], as amended [2], implement EC Directive 2002/49/EC [3] (END) on assessment and management of environmental noise in Ireland.

The aim of the END is to provide a common framework to avoid, prevent or reduce, on a prioritised basis, the harmful effects of exposure to environmental noise through the preparation of strategic noise maps and the development and implementation of action plans. EU Member States (MS) are currently implementing Round 4 (R4) of this noise mapping and action planning cycle (2020–2025).

In August 2011 the EPA published Version 2 of the “Guidance Note for Strategic Noise Mapping” [4] to provide practical information, advice and guidance to designated Noise Mapping Bodies (NMB) on the development of strategic noise maps under the Round 2 of the Environmental Noise Regulations.

Ahead of the Round 4 strategic noise mapping, it is planned to revise and update the EPA guidance in order to take into account the changes to the Directive, and other relevant progress related to the strategic noise mapping. The most significant changes to the Directive have been:

1 simon.shilton@acustica.co.uk

2 rafdouglas@gmail.com

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• Introduction of the common noise assessment methods for Europe (CNOSSOS-EU) through Di- rective 2015/996 [5], which repealed and replaced Annex II of the END; • Amending, for the purposes of adapting to scientific and technical progress, Annex II of the END (CNOSSOS-EU) through Delegated Directive (EU) 2021/1226 [6]; and • Introduction of the assessment methods for harmful effects of environmental noise through Di- rective 2020/367 [7], which repealed and replaced Annex III of the END. For the calculation of noise due to road traffic, the CNOSSOS-EU methodology includes a number of technical aspects which are different from the UK Calculation of Road Traffic Noise (CRTN) 1988 [8] method previously used for strategic noise mapping in Ireland. Where relevant it is proposed to investigate these key changes in order to inform the revised guidance to noise mapping bodies (NMBs) ahead of the R4 strategic noise mapping.

One such aspect is the inclusion of a correction to road traffic noise emissions to account for the effect of the acceleration and deceleration of vehicles near to junction. There are two versions of the correction factor, one for traffic light-controlled junctions, and one for roundabouts, whilst the Di- rective text indicates that they must be applied within 100 m of such junctions.

The aim of this technical investigation was to identify the effect of the correction factor on road traffic noise emissions, and determine whether there was a practical approach to implement the cor- rection factor within the upcoming noise mapping.

2. TRAFFIC LIGHT AND ROUNDABOUT JUNCTIONS

Within Directive 2015/996, Section 2.2 (pages 5 to 12) the methodology to calculate the sound power emission in octave bands for road traffic noise is set out. The December 2020 Delegated Directive amending Annex II has introduced some minor typographical amendments to Section 2.2.1, but there have been no amendments introduced to Section 2.2.5.

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Section 2.2.5 describes Effect of the acceleration and deceleration of vehicles, and states:

“Before and after crossings with traffic lights and roundabouts a correction shall be applied for the effect of acceleration and deceleration as described below.

The correction terms for rolling noise, ΔL WR,acc,m,k , and for propulsion noise, ΔL WP,acc,m,k , are linear functions of the distance x (in m) of the point source to the nearest intersection of the respective source line with another source line. They are attributed to all octave bands equally:

(1)

(2)

The coefficients C R,m,k and C P,m,k depend on the kind of junction k (k = 1 for a crossing with traffic lights; k = 2 for a roundabout) and are given for each vehicle category. The cor- rection includes the effect of change in speed when approaching or moving away from a crossing or a roundabout.

Note that at a distance |x| ≥ 100 m, ΔL WR,acc,m,k = ΔL WP,acc,m,k = 0.” In consideration of the described methodology, the following may be deduced.

Abynaint = Cant x Max(1 = EL 0) Alavracmt = Coma X Max(1 ~ 705

“Before and after crossings with traffic lights and roundabouts a correction shall be applied for the effect of acceleration and deceleration as described below.” “linear functions of the distance x (in m) of the point source to the nearest intersection of the respective source line with another source line.” This suggests that the correction applies to crossing with traffic lights where at least two roads in- tersect, which therefore would exclude light controlled pedestrian crossings.

"a correction shall be applied for the effect of acceleration and deceleration as described below” . This indicates that the inclusion of this correction is mandatory.

“Note that at a distance |x| ≥ 100 m, ΔL WR,acc,m,k = ΔL WP,acc,m,k = 0.” This indicates that the correction is only to be applied within 100 m of the junction.

3. APPROACH

In order to investigate the effect of acceleration and deceleration on the road traffic noise emission, and to develop a methodology for implementing the effect suitable for the revised noise mapping guidance, the following scope and methodology were developed.

The scope of the investigation into the effect of acceleration and deceleration aimed to address the following questions: • How does the correction factor vary with distance from the junctions? • Does the correction have an effect greater or smaller than the 2 dBA source effect threshold within the CNOSSOS-EU quality framework? (Directive 2015/996, Section 2.1.2 on page 5) • Could a working definition be developed for the type of junctions and roundabouts to be included within R4 noise mapping? • Where can data on junction types be found in Ireland? • How could junction type be assigned in the noise models? • How should the noise calculation model be constructed to correctly implement the correction factor set out in the methodology? 4. EFFECT OF THE ACCELERATION AND DECELERATION OF VEHICLES

4.1. Model description In order to understand the magnitude of the correction terms, two different approaches have been used an analytical approach was taken to calculate the effect on the road traffic noise emission level within 150 m of the crossings and roundabouts.

In order to gain an understand of how the traffic noise emission levels are affected by the correction factors, a simple example has been developed using the CNOSSOS-EU:2020 calculation method, including the Delegated Directive amendments, based on the default traffic flows and %HGVs rec- ommended within WG-AEN GPG v2 [9] Tools 2.5 and 4.5, shown in Table 1.

These traffic flow compositions are used only to undertake an analytical investigation into the effect of the junction corrections across a range of traffic flow volumes. It is not intended to imply that these traffic flows in any way reflect actual traffic flows in Ireland, or that they should be assigned to roads within the R4 strategic noise mapping. For example, it would not be expected to assign a junction correction to a motorway, as the main carriageways do not have traffic light controlled junc- tions or roundabouts.

For each of the seven traffic flows, 45 road segments were created which were assigned one of the three junction types, with the distance to the junction set in 10 m intervals from 10 to 150 m.

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For each road/junction type/junction distance combination, a receiver was placed at the centre of the road segment, a fixed distance of 10 m from the road centreline. The complete model comprised a total of 315 roads, and 315 receivers.

Table 1: WG-AEN GPG v2 default traffic flows, with adaptions

Road type Period traffic flow Hourly traffic flow Annual Day Eve Night Day Eve Night Traffic flow Dead-end roads 175 50 25 14.6 12.05 3.1 91,250 Service roads 350 100 50 29.2 25 6.3 182,500 Collecting roads 700 200 100 58.3 50 12.5 365,000 Small main roads 1400 400 200 116.7 100 25 730,000 Main road 2800 800 400 233.3 200 50 1,460,000 Major main road 5753 1644 822 479.4 411 102.8 3,000,000 Motorway 11507 3288 1644 958.9 822 205.5 6,000,000 Notes:

1) For “Main road” WG-AEN recommends traffic counts are undertaken, for the purpose of this simple example the doubling per category has been continued 2) For “Major main road” a total annual flow of 3 million vehicles has been di- vided using the same ratios as for the other categories 3) For “Motorway” a total annual flow of 6 million vehicles has been divided using the same ratios as for the other categories

4.2. Results of the analysis The following charts show the results of the analysis performed. Figures 1 and 2 present the results by junction type, and road traffic flow. It can be seen that for both junction types, the effect of the correction progressively drops to zero as the distance from the junction approaches 100 m, and the overall effect of the correction for traffic light intersections is greater than the correction for rounda- bouts.

Correction Factors for Intersections As a function of distance from the intersection

6,0

5,0

Dead-end road Service road Collecting road Small main road Main road Major main road Motorway

4,0

Delta Lden [dB(A)]

3,0

2,0

1,0

0,0

-1,0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 -2,0

Distance [m]

Figure 1: Change in L den near to traffic light-controlled junctions

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Correction Factors for Roundabouts As a function of distance from the roundabout

2,5

2,0

Dead-end road Service road Collecting road Small main road Main road Major main road Motorway

1,5

Delta Lden [dB(A)]

1,0

0,5

0,0

-0,5

-1,0

20 30 40 50 60 70 80 90 100 110 120 130 140 150 -1,5

Distance [m]

Figure 2: Change in L den near to roundabouts The Figures also indicate that the correction factors increase the noise levels for the examples with lower traffic flows, and decreases the noise levels for the examples with higher traffic flows. 5. LOCATION OF TRAFFIC LIGHT AND ROUNDABOUT JUNCTIONS

In order to incorporate the effect of traffic light and roundabout junctions into the noise mapping, it is necessary to identify the location of relevant traffic light and roundabout junctions within the road traffic noise model.

Within the Dublin noise agglomeration Sydney Coordinated Adaptive Traffic System (SCATS) sensors are located across Dublin City Council (DCC) and parts of Dún Laoghaire-Rathdown County Council (DLRCC). Smart Dublin [10] provides a dataset of inferred traffic light locations based on SCATs sensors typically being co-located at junctions with traffic lights, however it does not cover the whole of Dublin noise agglomeration, and there is currently no equivalent in Cork or Limerick.

Alternatively, it may be possible to manually identify the locations of crossings and roundabouts from field surveys, aerial photography or local knowledge, however the data capture process and manual editing of models across the cities of Cork, Dublin and Limerick would pose a resource in- tensive and costly undertaking.

Therefore, it is seen as desirable to identify the location of traffic light controlled junctions and roundabouts based upon existing spatial datasets, rather than through manual processing. Two possi- ble sources of data were identified, namely Ordnance Survey Ireland’s PRIME2 [11] database, and OpenStreetMap [12].

5.1. OSi PRIME2 Since 2017 the National Mapping Agreement [13] (NMA) has given government departments and Public Sector Bodies (PSB’s), unrestricted access to most of Ordnance Survey Ireland’s (OSi) geo- spatial data.

The OSi spatial data delivered under the NMA can support mapping, data analytics, scenario mod- elling and decision making. In the context of the END, it can support the development of strategic noise mapping across Ireland on a consistent basis, underpinned by national coverage data available to all the NMBs.

In order to search for the location of traffic light and roundabout junctions, the current version of OSi PRIME2 held by the EPA (November 2020) was queried. Three different themes within OSi PRIME2 contained objects which were assigned attributes relating to roundabouts, namely OSi

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PRIME2 WAY_PNT (points), WAY_GDF1 (lines), and WAY_POLY (areas), have the following attributes within the FORM_ID field: 330 Roundabout; 471 Crossroads; 476 Roundaboutmini; 480 TJunction; 484 YJunction; 489 Sliproad Junction; 490 Multi Junction; 505 On/Off Ramp Junction.

The relevant objects within each dataset were identified to determine if they could be used within an automated means of preparing the road traffic model in GIS.

While the OSi PRIME2 database provided three different means of identifying the locations of roundabouts, there was no specific object or attribution identified which could locate traffic light controlled junctions. This led onto the OpenStreetMap database as an alternative source of mapping information.

5.2. OpenStreetMap OpenStreetMap is open data, built by a community of mappers that contribute and maintain data about roads, trails, cafés, railway stations, and much more, all over the world. OpenStreetMap data may be used for any purpose, without cost, under the terms of the Open Data Commons Open Data- base License (ODbL) [14], provided that any use references OpenStreetMap as the source of the data used.

Searching the OpenStreetMap data it is possible to find the “highways = traffic signals” tags, which are used to identify the locations of traffic lights. With suitable design of the query, it is pos- sible to exclude traffic signals for pedestrians and cyclists which can be tagged separately within OpenStreetMap.

5.3. PREPARATION OF TRAFFIC LIGHT CONTROLLED JUNCTIONS AND ROUND- ABOUTS DATASETS Having identified sources of data on the location of traffic light controlled junctions and roundabouts, it was necessary to develop a methodology to extract and use this data in the development of the noise calculation model. The aim was to develop a process which is straightforward to follow, low cost to implement, and may be used in any mapping region in Ireland.

A methodology was developed which splits the road centreline within 100 m of traffic light and roundabout junctions into 10 m long segments, and sets the “distance to junction” value separately for each as appropriate. A detailed methodology was prepared based on a free and open source GIS which should be accessible to all Noise Mapping Bodies. It should be noted that the optimal length of segmentation was not investigated, and it could be that 20 m or 33.33 m segments would be ac- ceptable.

6. CONCLUSIONS

This technical investigation has concluded that correction for the effects of acceleration and deceler- ation in the vicinity of traffic light and roundabout junctions can be applied for strategic noise map- ping of roads in Ireland under Directive 2015/996.

In order to support NMBs, this technical investigation of the correction factor for roads within 100 m of traffic light and roundabout junctions has:

• Presented a detailed illustration of the effect on noise emission introduced by the corrections; • Identified the location of traffic light and roundabout junctions in datasets accessible to NMBs in Ireland; • Presented methodologies for preparing a junction locations dataset, and for preparing road cen- trelines for noise modelling to include the correction for traffic light and roundabout junctions; and

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• The methodologies presented are based on a free and open-source GIS which should be accessi- ble to all Noise Mapping Bodies, or which may be adapted to proprietary GIS as necessary.

The technical investigation has shown that for the examples with lower traffic flows, below ap- proximately AADT of 2,000 veh/24hr, the effect on the noise emission level is greater approaching traffic light controlled junctions than approaching roundabouts, up to double the increase.

For the examples with higher traffic flows, above approximately AADT of 4,000 veh/24hr, a re- duction in overall emission occurs near to the junctions, with the greater reductions approaching roundabouts, rather than approaching traffic light controlled junctions.

It has been shown that for traffic flows below approximately AADT of 2,000 veh/24hr, the cor- rection factor for traffic light controlled junctions can be above 2.0 dBA. For roundabouts, the cor- rection is only above 2.0 dBA within 30 m of the roundabout for the lowest example traffic flow of AADT 250 veh/24hr. This suggests that when the traffic flow is less than approximately 4,000 vehi- cles AADT, the correction for traffic light controlled junctions may not be omitted, as it has more than a 2.0 dBA effect on the emission level referred to in Section 2.1.2 of the Directive 2015/996. If NMBs include such low traffic flow roads within the R4 strategic noise mapping of agglomerations, the model should include the correction for traffic light-controlled junctions in order to meet the requirements of the Directive.

It has also been shown that suitable data is available to identify the location of the relevant junc- tions without data licensing costs to the noise mapping bodies, that the model can be prepared using commonly available GIS. It is estimated it may could take approximately 5 working days to prepare traffic light junctions and roundabouts across each local authority area within an agglomeration.

7. ACKNOWLEDGEMENTS

We gratefully acknowledge the support of the Environmental Protection Agency for commissioning the technical investigation. 8. REFERENCES

1. European Communities (Environmental Noise) Regulations 2018, S.I. No. 549 of 2018. 2. European Communities (Environmental Noise) (Amendment) Regulations 2021, S.I. No.

663/2021. 3. Directive 2002/49/EC of the European Parliament and of the Council of 25 June 2002 relating

to the assessment and management of environmental noise, Official Journal of the European Communities, L 189/12-25, 18 th July 2002. 4. Guidance Note for Strategic Noise Mapping for the Environmental Noise Regulations 2006,

Version 2, August 2011, Environmental Protection Agency. 5. Commission Directive (EU) 2015/996, The European Commission, May 2015. 6. Commission Delegated Directive (EU) 2021/1226 of 21.12.2020 amending, for the purpose of

adapting to scientific and technical progress, Annex II of Directive 2002/49/EC of the European Parliament and the Council as regards common noise assessment methods. 7. Commission Directive (EU) 2020/367 of 4 March 2020 amending Annex III to Directive

2002/49/EC of the European Parliament and of the Council as regards the establishment of as- sessment methods for harmful effects of environmental noise 8. Department of Transport, Calculation of Road Traffic Noise (CRTN), HMSO, 1988.

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9. European Commission Working Group Assessment of Exposure to Noise (WG-AEN), Position

Paper, Good Practice Guide for Strategic Noise Mapping and the Production of Associated Data on Noise exposure, Version 2, August 2007. 10. https://data.smartdublin.ie/dataset/traffic-lights-locations 11. https://osi.ie/wp-content/uploads/2018/04/PRIME2-Client-Documentation-Concepts-V-02.4.pdf 12. https://www.openstreetmap.org/ 13. https://osi.ie/services/national-mapping-agreement/ 14. https://opendatacommons.org/licenses/odbl/summary/

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