Table of Contents

    Topic review

    Roundabout

    Subjects: Transportation
    View times: 4
    Submitted by: Saša Ahac

    Definition

    Challenges that emerge in roundabout design are mostly related to space constrictions and provision of appropriate deflection around the central island. This can result in speed profiles on roundabouts that might reduce their potential as a noise abatement measure. Because of this, the impact of a roundabout on noise levels and its applicability as a traffic calming device and a noise abatement measure should be investigated in the early design stage, by modeling noise levels.

    1. Introduction

    The goal of sustainable transportation is to protect the environment and conserve resources while taking into consideration societal needs as well as benefits and costs [1]. Numerous studies have shown that the abovementioned sustainability goals can be achieved in road traffic network planning, design, and management by the introduction of modern roundabouts in the road network. According to [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], these intersections have proven to be very successful at improving safety (due to the reduced number of conflict points and lower speed compared to the traditional intersections) while enhancing mobility by reducing the total delay compared to other controlled intersections. Moreover, modern roundabouts usually perform better than traditional intersections with traffic lights in terms of environmental sustainability. Previous studies have shown that the application of roundabouts can help reduce the excessive emissions and fuel consumption associated with idling time, acceleration, and deceleration of vehicles that usually occur on traditional intersections with traffic lights, as well as noise pollution in the vicinity of road intersections. Reported average reductions varied from 21 to 42% in emissions of carbon monoxide, 16–59% in emissions of carbon dioxide, 20–48% in emissions of oxides of nitrogen, 18–65% in emissions of hydrocarbons, and from 1 to 4 dB(A) in noise emission [2][9][11][12][13][16][17][18][19][20][21][22][23][24][25][26].

    2. Modeling the Influence of Roundabout Deflection on Its Efficiency as a Noise Abatement Measure

    Since noise pollution is still considered a major environmental health problem in Europe [27], and since road traffic is the dominant noise source in urban and suburban areas, the noise abatement opportunities should be an integral part of every road planning, design and/or reconstruction process. In urban areas, the average vehicle speed is low (50 km/h or lower), so the road traffic noise level is influenced by vehicle speed, acceleration, and deceleration [18][28][29]. To achieve a required reduction in noise levels, it is necessary to match the physical layout of the road to the intended speed and to provide as smooth a driving pattern as possible [18]. Modern roundabout, as a traffic calming device on which operating speed depends on the geometry (deflection around the circular island) [30][31], and a device that can carry smooth traffic flow by minimizing the start–stop operations of drivers, fulfills the abovementioned requirements for the effective noise abatement measure.

    A smooth speed profile through the roundabout is achieved by ensuring the clarity of the situation for approaching drivers, visibility between road users, comprehensibility of traffic operations, and appropriate accommodation of the design vehicles. This means that the impact of a modern roundabout on noise reduction is directly linked to the quality of its design. Roundabout design is an iterative process that consists of the identification of initial design elements, performance checks (the design vehicle swept path analysis, the definition of the fastest path, and visibility tests), and final design details. A good design results in the smooth curvature, channelization, and deflection required to achieve consistent speeds, and appropriate sight distance. As mentioned above, to achieve the required reduction in vehicular emissions, the speed profile through the roundabout must be as smooth as possible [32][33][34]. This can be ensured in the roundabout’s designing phase by conducting the abovementioned performance checks, specifically the definition of the fastest path through the roundabout. This performance check aims to determine the negotiation speed for a particular movement into, through, and exiting the roundabout, and the relative speed between consecutive geometric elements as well as between conflicting traffic movements. If the determined relative speed is high, large decelerations and accelerations will occur, which will result in negative impacts on drivers and on the road environment. Therefore, according to [30], the maximum relative speed on traffic calming devices such as roundabouts should be less than 20 km/h.

    Environmental benefits of the introduction of modern roundabouts in the road network in terms of their noise reduction capabilities can be determined either by field measurements [2][11][12][13][22][24][26][35][36][37][38][39][40] or by physical modeling, using established or new noise models that are verified by field measurements [16][21][26][41][42][43][44][45][46][47][48]. The most important attributes of traffic influencing the noise are traffic flow, vehicle speed, and percentage of heavy vehicles, and these attributes are incorporated in established traffic noise emission models to a varying degree of detail [49][50][51][52]. Problems that emerge while modeling noise at roundabouts relate primarily to capturing the impact of their specific traffic flow conditions in the noise emission model. These specific traffic flow conditions are minimized start–stop operations and queuing, as well as the smaller average speed of approaching and passing traffic compared to the traditional intersections with traffic lights.

    Depending on the way noise models account for traffic flow, the temporal and spatial variations in vehicle kinematics at intersections are more-or-less accurately captured. In static noise models, roads are divided into sections where traffic flow is considered smooth and homogeneous. These noise models usually include a propagation correction term for noise levels in the vicinity of an intersection, the value of which depends on the distance to the intersection [49][50]. Analytic noise models attempt to capture the impact of interrupted traffic on the average vehicle speed profile. They split each road section into subsections where vehicles are assumed to have a constant average speed and homogeneous traffic flow conditions [50]. Dynamic noise models or micro-simulation noise models are based on a dynamic traffic model, and as such can capture the specific traffic flow conditions in the vicinity of intersections [50][53][54][55][56][57][58].

    The usability of each noise model depends on its reliability and accuracy. According to the previous studies, static models usually underestimate the noise levels compared to the analytic and dynamic noise models [50]. On the other hand, previous studies have shown that the increased complexity of a model that includes more physical phenomena and effects will not automatically produce better results in terms of model accuracy [51][59]. The optimal model is one in which the reliability of the result is harmonized with the available input data, and the costs and time required to create a noise model. Based on that, a static noise model RLS-90 was selected as a baseline for road traffic noise calculations conducted in the research presented in this paper. Previous research showed that modifications of the standard RLS-90 model can result in the reduction of differences between measured and calculated noise levels ranging from 1.0 to 2.8 dB(A) for streets and intersections [60][61]. However, the modifications concerning the position of noise sources showed to be too detailed and time-consuming when modeling traffic noise at roundabouts, especially roundabouts with more than one entry and exit lane. Another issue with these modifications is that they do not represent real traffic flow conditions at roundabouts, especially concerning the movement trajectories of vehicles negotiating these types of intersections.

    3. Conclusions

    Challenges that emerge in roundabout design are mostly related to space constrictions and the provision of appropriate deflection around the central island. This can result in inappropriate speed profiles on roundabouts that might reduce their potential as a noise abatement measure. Therefore, the impact on noise levels and its applicability as a traffic calming device should be investigated in the early design stage of a roundabout, by modeling road traffic noise levels. Established noise models used in noise prediction are either too complex for use in the preliminary design stage of roundabouts when the available input data is limited, or they do not even include intersection contribution to noise levels. At the same time, their creation can be rather time-consuming. This makes them less than optimal for use in noise predictions at roundabouts, as an optimal model is the one in which the reliability of the result is harmonized with the available input data, and the costs and time required to create a noise model.

    In order to simplify the preparation procedure of the noise emission model and allow the simulation of the impact of the intersection on the noise situation in the early stages of roundabout design, the following results of the fastest path performance check could be utilized for noise calculations at suburban roundabouts with unsaturated traffic flow: vehicle movement trajectories (for the position of road traffic noise sources), and design speed (for noise calculations at roundabouts that are still in the design phase). These modifications result in a model that is close to the real world in terms of traffic flow conditions and enable modeling the influence of roundabout deflection on calculated noise levels. Also, these modifications should encourage the optimization of roundabout geometry in its preliminary design phase not only in terms of safety, but also in terms of its noise reduction capabilities, and/or emissions in general.

    The entry is from 10.3390/su13105407

    References

    1. Ariniello, A.; Przybyl, B. Roundabouts and Sustainable Design. In Proceedings of the Green Streets and Highways 2010: An Interactive Conference on the State of the Art and How to Achieve Sustainable Outcomes, Denver, CO, USA, 14–17 November 2010; Weinstein, N., Ed.; American Society of Civil Engineers (ASCE): Reston, VA, USA, 2010.
    2. Hydén, C.; Várhelyi, A. The effects on safety, time consumption and environment of large scale use of roundabouts in an urban area: A case study. Accid. Anal. Prev. 2000, 32, 11–23.
    3. Lenters, M. Roundabout Planning and Design for Efficiency & Safety Case study: Wilson Street/Meadowbrook Drive/Hamilton Drive, City of Hamilton. In Proceedings of the 2003 Annual Conference of the Transportation Association of Canada (TAC), St. John’s, NL, Canada, 21–23 September 2003; Available online: (accessed on 4 April 2021).
    4. Lenters, M. Safety Auditing Roundabouts. In Proceedings of the 2004 Annual Conference of the Transportation Association of Canada (TAC), Québec City, QC, Canada, 19–22 September 2004; Available online: (accessed on 4 April 2021).
    5. Bergh, C.; Retting, R.A.; Myers, E. Continued Reliance on Traffic Signals: The Cost of Missed Opportunities to Improve Traffic Flow and Safety at Urban Intersections; Insurance Institute for Highway Safety: Arlington, VA, USA, 2005; Available online: (accessed on 4 April 2021).
    6. Quartieri, J.; Mastorakis, N.E.; Guarnaccia, C.; Troisi, A.; D′Ambrosio, S.; Iannone, G. Road Intersections Noise Impact on Urban Environment Quality. In Proceedings of the 5th WSEAS International Conference on Recent Advances in Applied and Theoretical Mechanics, Puerto De La Cruz, Tenerife, Canary Islands, Spain, 14–16 December 2009.
    7. Granà, A.; Giuffrè, T.; Guerrieri, M. Exploring Effects of Area-Wide Traffic Calming Measures on Urban Road Sustainable Safety. J. Sustain. Dev. 2010, 3, 38–49.
    8. Covaciu, D.; Florea, D.; Preda, I.; Timar, J. The Effect of Converting a Signalized Intersection into a Roundabout—A Case Study. In Proceedings of the International Congress on Automotive CAR-2011, Pitesti, Romania, 2–4 November 2011; Available online: (accessed on 4 April 2021).
    9. Mensah, S.; Eshragh, S.; Faghri, A. Modern Roundabouts and Sustainable Intersection Design. In Proceedings of the 3rd International Conference on Roundabouts, TRB, Carmel, IN, USA, 18–20 May 2011.
    10. Mauro, R.; Cattani, M. Functional and Economic Evaluations for Choosing Road Intersection Layout. Promet Traffic Transp. 2012, 24, 441–448.
    11. Guerrieri, M.; Corriere, F.; Casto, B.L.; Rizzo, G. A model for evaluating the environmental and functional benefits of ‘‘innovative’’ roundabouts. Transp. Res. Part D 2015, 39, 1–16.
    12. Guerrieri, M.; Corriere, F.; Rizzo, G.; Casto, B.L.; Scaccianoce, G. Improving the Sustainability of Transportation: Environmental and Functional Benefits of Right Turn By-Pass Lanes at Roundabouts. Sustainability 2015, 7, 5838–5856.
    13. Distefano, N.; Leonardi, S. Experimental investigation of the effect of roundabouts on noise emission level from motor vehicles. Noise Control Eng. J. 2019, 67, 282–294.
    14. Fernandes, P.; Teixeira, J.; Guarnaccia, C.; Bandeira, J.M.; Macedo, E.; Coelho, M.C. The Potential of Metering Roundabouts: Influence in Transportation Externalities. TRR J. Transp. Res. Board 2018, 2672, 21–34.
    15. Ahmed, H.; Easa, S. Optimization of single-lane roundabout geometric design: Environmental sustainability. In Proceedings of the CSCE 2018 Annual Conference, Fredericton, NB, Canada, 13–16 June 2018.
    16. Bérengier, M. Acoustical impact of traffic flowing equipments in urban area. In Proceedings of the Forum Acusticum, Sevilla, Sevilla, Spain, 16–20 September 2002.
    17. Mandavilli, S.; Russell, E.R.; Rys, M.J. Impact of Modern Roundabouts on Vehicular Emissions. In Proceedings of the 2003 Mid-Continent Transportation Research Symposium, Ames, IA, USA, 21–22 August 2003.
    18. Bendtsen, H.; Haberl, J.; Litzka, J.; Pucher, E.; Sandberg, U.; Watts, G. Traffic Management and Noise Reducing Pavements—Recommendations on Additional Noise Reducing Measures; Report 137; Danish Road Institute: Roskilde, Denmark, 2004.
    19. Annecke, R.; Berge, T.; Crawshaw, S.; Ellebjerg, L.; Mårdh, S.; Pullwitt, E.; Steven, H.; Wiberg, A.; Zimmermann, U. Noise Reduction in Urban Areas from Traffic and Driver Management; EU Project Silence, Deliverable No. H.D2; Ellebjerg, H., Ed.; European Commission: Brussels, Belgium, 2005.
    20. Desarnaulds, V.; Monay, G.; Carvalho, A. Noise reduction by urban traffic management. In Proceedings of the Journées d’Automne 2004—Société Suisse d’Acoustique, Jona, St. Gallen, Switzerland, 4–5 November 2004; Available online: (accessed on 4 April 2021).
    21. Makarewicz, R.; Golebiewski, R. Modeling of the roundabout noise impact. J. Acoust. Soc. Am. 2007, 122, 860–868.
    22. Decký, M. Noise pollution from roundabout traffic in the outer environment of built-up areas of towns. Perner’s Contacts 2009, 4, 53–68. Available online: (accessed on 4 April 2021).
    23. Fernandes, P.M.; Fontes, T.; Neves, M.; Pereira, S.R.; Bandeira, J.; Rouphail, N.; Coelho, M. Assessment of Corridors with Different Types of Intersections. Transp. Res. Rec. 2015, 2503, 39–50.
    24. Gardziejczyk, W.; Motylewicz, M. Noise level in the vicinity of signalized roundabouts. Transp. Res. Part. D 2016, 46, 128–144.
    25. Meneguzzer, C.; Gastaldi, M.; Arboretti Giancristofaro, R. Before-and-After Field Investigation of the Effects on Pollutant Emissions of Replacing a Signal-Controlled Road Intersection with a Roundabout. J. Adv. Transp. 2018, 2018, 3940362.
    26. Jandacka, D.; Decky, M.; Durcanska, D. Traffic Related Pollutants and Noise Emissions in the Vicinity of Different Types of Urban Crossroads. IOP Conf. Ser. Mater. Sci. Eng. 2019, 661, 012152.
    27. European Environment Agency (EEA). Managing Exposure to Noise in Europe. Briefing January 2017. Available online: (accessed on 2 May 2020).
    28. Robertson, S.; Ward, H.; Marsden, G.; Sandberg, U.; Hammerstrom, U. The Effect of Speed on Noise, Vibration and Emissions from Vehicles; Working Paper 1.2.1 for the Master Project Funded by the European Commission (Contract No RO-96-SC.202); European Commission: Brussels, Belgium, 1998.
    29. Covaciu, D.; Florea, D.; Timar, J. Estimation of the Noise Level Produced by Road Traffic in Roundabouts. Appl. Acoust. 2015, 98, 43–51.
    30. Brindle, R.E. Speed-Based Design of Traffic Calming Schemes. In Proceedings of the ITE 2005 Annual Meeting and Exhibit Compendium of Technical Papers, Melbourne, Australia, 7–10 August 2005.
    31. Davidović, S.; Bogdanović, V.; Garunović, N.; Papić, Z.; Pamučar, D. Research on Speeds at Roundabouts for the Needs of Sustainable Traffic Management. Sustainability 2021, 13, 399.
    32. Coelho, M.C.; Farias, T.L.; Rouphail, N.M. Effect of roundabout operations on pollutant emissions. Transp. Res. Part D 2006, 11, 333–343.
    33. Chamberlin, R.; Swanson, B.; Talbot, E.; Dumont, J.; Pesci, S. Analysis of MOVES and CMEM for evaluating the emissions impacts of an intersection control change. In Proceedings of the TRB 90th Annual Meeting: Current Environmental Issues in Transportation, Washington, DC, USA, 23–27 January 2011.
    34. Ahn, K.; Kronprasert, N.; Rakha, H. Energy and Environmental Assessment of High-Speed Roundabouts. Transp. Res. Rec. 2009, 2123, 54–65.
    35. Waters, P.E. Control of road noise by vehicle operation. J. Sound Vib. 1970, 13, 445–453.
    36. Lewis, P.T.; James, A. On the noise emitted by single vehicles at roundabouts. J. Sound Vib. 1978, 58, 293–299.
    37. Hallmark, S.L.; Wang, B.; Mudgal, A.; Isebrands, H. On-Road Evaluation of Emission Impacts of Roundabouts. TRR J. Transp. Res. Board 2011, 2265, 226–233.
    38. Lu, X.; Kang, J.; Zhu, P.; Cai, J.; Guo, F.; Zhang, Y. Influence of Urban Road Characteristics on Traffic Noise. Transp. Res. Part D Transp. Environ. 2019, 75, 136–155.
    39. Trollé, A.; Terroir, J.; Lavandier, C.; Marquis-Favre, C.; Lavandier, M. Impact of urban road traffic on sound unpleasantness: A comparison of traffic scenarios at crossroads. Appl. Acoust. 2015, 94, 46–52.
    40. Campolieti, D.; Bertoni, D. The Action Plan for Noise Reduction in Modena: Methods, Effects and Perspectives. Radiat. Prot. Dosim. 2009, 137, 252–255.
    41. Guarnaccia, C. Acoustical Noise Analysis in Road Intersections: A Case Study. Recent advances in Acoustics and Music. In Proceedings of the 11th WSEAS International Conference on Acoustics & Music: Theory & Applications (AMTA ′10); WSEAS Press: Athens, Greece, 2010; pp. 208–215.
    42. Estévez-Mauriz, L.; Forssén, J.; Kropp, W.; Zachos, G. Isolating Key Features in Urban Traffic Dynamics and Noise Emission: A Study on a Signalized Intersection and a Roundabout. In Proceedings of the 45th International Congress and Exposition on Noise Control Engineering (Internoise 2016): Towards a Quieter Future, Hamburg, Germany, 21–24 August 2016; Deutsche Gesellschaft für Akustik (DEGA): Berlin, Germany, 2016; pp. 7197–7208.
    43. Estévez-Mauriz, L.; Forssén, J. Dynamic traffic noise assessment tool: A comparative study between a roundabout and a signalised intersection. Appl. Acoust. 2018, 130, 71–86.
    44. Li, F.; Lin, Y.; Cai, M.; Du, C. Dynamic simulation and characteristics analysis of traffic noise at roundabout and signalized intersections. Appl. Acoust. 2017, 121, 14–24.
    45. Jaworski, A.; Mądziel, M.; Lejda, K. Creating an emission model based on portable emission measurement system for the purpose of a roundabout. Environ Sci. Pollut. Res. 2019, 26, 21641–21654.
    46. Pigasse, G. Traffic Flow and Noise: A Method Study; Report 180—2010, Road Directorate; Danish Road Institute: Roskilde, Denmark, 2010; ISBN 978-87-92094-63-6.
    47. Salamati, K.; Rouphail, N.M.; Frey, H.C.; Liu, B.; Schroeder, B.J. Simplified Method for Comparing Emissions in Roundabouts and at Signalized Intersections. Transp. Res. Rec. J. Transp. Res. Board 2015, 2517, 48–60.
    48. To, W.M.; Chan, T.M. The noise emitted from vehicles at roundabouts. J. Acoust. Soc. Am. 2000, 107, 2760–2763.
    49. Steele, C. A critical review of some traffic noise prediction models. Appl. Acoust. 2001, 62, 271–287.
    50. Chevallier, E.; Can, A.; Nadji, M.; Leclercq, L. Improving noise assessment at intersections by modeling traffic dynamics. Transp. Res. Part D 2009, 14, 100–110.
    51. Probst, W. Accuracy and Precision in Traffic Noise Prediction. In Proceedings of the Internoise 2010 Noise and Sustainability, Lisbon, Portugal, 13–16 June 2010; Available online: (accessed on 4 April 2021).
    52. Garg, N.; Maji, S. A critical review of principal traffic noise models: Strategies and implications. Environ. Impact Assess. Rev. 2014, 46, 68–81.
    53. Can, A.; Leclercq, L.; Lelong, J. Dynamic estimation of urban traffic noise: Influence of traffic and noise source representations. Appl. Acoust. 2008, 69, 858–867.
    54. Can, A.; Leclercq, L.; Lelong, J.; Defrance, J. Capturing urban traffic noise dynamics through relevant descriptors. Appl. Acoust. 2008, 69, 1270–1280.
    55. Can, A.; Leclercq, L.; Lelong, J.; Defrance, J. Accounting for traffic dynamics improves noise assessment: Experimental evidence. Appl. Acoust. 2009, 70, 821–829.
    56. Can, A.; Chevallier, E.; Nadji, M.; Leclercq, L. Dynamic Traffic Modeling for Noise Impact Assessment of Traffic Strategies. Acta Acust. United Acust. 2010, 96, 482–493.
    57. Guarnaccia, C. Advanced Tools for Traffic Noise Modelling and Prediction. WSEAS Trans. Syst. 2013, 2, 121–130. Available online: (accessed on 5 April 2021).
    58. Zhang, X.; Kuehnelt, H.; De Roeck, W. Traffic Noise Prediction Applying Multivariate Bi-Directional Recurrent Neural Network. Appl. Sci. 2021, 11, 2714.
    59. Probst, W. Accuracy and precision of prediction models for road noise. In Proceedings of the EuroNoise 2009, Edinburgh, UK, 26–29 October 2009.
    60. Dragčević, V.; Ahac, S.; Stančerić, I. Experience in estimation of road traffic noise situation in urban zone. In Proceedings of the 16th International Congress on Sound & Vibration, Recent Developments in Acoustics, Noise and Vibration, Krakow, Poland, 5–9 July 2009.
    61. Džambas, T.; Dragčević, V.; Čuljak, J. Monitoring of traffic noise on urban road intersection—A Case Study. In Proceedings of the 5th International Conference on Road and Rail Infrastructure, Zadar, Croatia, 17–19 May 2018; Available online: (accessed on 5 April 2021).
    More
    1. Please check and comment entries here.