traffic noise mapping in galle city - sri lanka

Special Sessions on Green Technology & Green Energy 5th International Conference on Sustainable Built Environment 2014, Kandy, Sri Lanka, 12th to 15th December 2014

SBE/14/8

TRAFFIC NOISE MAPPING IN GALLE CITY - SRI LANKA S.M.N. Sethunga*, J.A.P. Bodhika and W.G.D. Dharmaratna University of Ruhuna, Matara, Sri Lanka *E-Mail: [email protected], TP: +94 712054185 Abstract:

Unwanted, unpleasant and disturbing sound is called noise. Noise could course harm

problem in the world. These noises can be mapped quantitatively and such a map is called a noise map. Noise maps are often used in Environmental Impact Assessment while planning and maintaining cities. A noise map of Galle city, the capital city of the Southern Province of Sri Lanka, is produced to study the variation of the noise level in the city. Noise measurements were carried out during the month of November 2013, using a B&K Type-2250 hand held analyser (IEC 61672-1; 2002 Class1). A-weighted, equivalent continuous sound pressure level (LAeq) of diurnal sound level variation was measured. Internationally recommended IMMI mapping software was used to prepare the noise map. The traffic volume, vehicular type, their speed, nature of road surface and meteorological conditions were considered. According to the results, 76.3±5.4 % of the total area of 42.16 km2 of Galle city (suburbs of A2, A17, B41, B109, B128, B129 and B130 roads), the noise level is exceeding the maximum allowed level for residential areas (63 dB of Sri Lanka National Environment Act. No. 47, 1980). Densely populated areas of the city lie within the noise contour of 75-80 dB. LAeq was exceeding 80 dB level at some locations due to saturated traffic, especially, along a portion of A2 road within the city which can be reduced by increasing the number of lanes. The results suggest that necessary actions have to be taken to reduce the sound pollution in order to provide better living conditions to the citizens. Keywords:

Galle City, LAeq, Noise map, Traffic noise. headache, blood pressure, and heart failure etc. due to increase of heart beat and constriction of blood vessels. Noise may cause damage to liver, brain and heart [3]. The internationally used parameter for noise level analysis is Leq, the equivalent continuous sound pressure level

1. Introduction & Literature Review An unwanted unpleasant sound is called noise. Human activities produce various sounds at different levels especially due to transportation, machines used in industries and in construction sites etc. Noise pollution is one of the major environmental problems in many cities with the rapid urbanization. Noise could cause annoyance, aggression, hypertension, high stress levels, tinnitus, hearing loss, sleep disturbances, and other harmful effects, disrupting physiological and psychological health of civilians living in noisy areas. Especially, the level of noise exposure and the period of noise exposure are very important in human health [1]. The impact of road traffic noise on human health has been well reviewed [2]. Environmental noise leads to emotional and behavioural stress. Noise increases the chances of occurrence of diseases such as

which has the same total energy as the actual Additionally Lmax, Ldn (L day & night) and L10 (percentile L) are used at some instances for noise mapping [4]. The perceived noise level by human ear over given time period is accounted by A-weighted equivalent continuous sound pressure level (L Aeq) or with maximum average sound pressure level LAmax [1]. A-weighting is applied to instrumentmeasured sound levels in effort to account for the relative loudness perceived by the human ear.

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Road, rail and air traffic noise plays an important role in environmental noise and its pollution. Road traffic noise is almost one of the dominant sources of noise pollution in main cities in Sri Lanka. It has been reported [1] that more than half of all European Union citizens are estimated to live in zones that do not ensure acoustical comfort level to residents. More than 30% are exposed to traffic noise, L Aeq exceeding 55 dB(A) at night, which could cause sleeping disorders. The noise due to road traffic alone could cause problems in many cities and about 40% and 20% of the population in the European Union expose to daytime road traffic noise exceeding 55 dB(A) and 65 dB(A), respectively. The impact of road traffic noise on human health has been reviewed [2] and its side effects on civilians have been well discussed [1].

several attempts [9] have been made to predict the noise levels in a given region. Especially, some models [10] have been developed to construct noise maps. The most familiar way of preparing the noise maps in many countries is to measure Lden or LAeq values with traffic volume, engine power, vehicle speed, type of vehicles, nature of road surface, etc. [11]. Noise maps play a major role in planning, tourism, leisure, transportation, investment and other developments in cities. These maps have been used in Environment Impact Assessments (EIA) and they provide a great remark of wellbeing of future generation in cities. The increase of number of vehicles directly contributes to increase the road traffic noise [12]. The number of vehicles registered in Sri Lanka, which has been increased by approximately 10 % annually during last few years, was 5.07 million at the end of July 2013 [13]. However, there is a very few number of research publications on noise pollution in Sri Lanka ([14], [15], [16], [17], [18]). A noise map of Matara city, Sri Lanka, published recently, has indicated that some schools, hospitals, offices, and religious places are located within 75-80 dB(A) noise contours [15]. This result shows the necessity of such studies in urban cities in Sri Lanka and the importance of using noise maps for development of cities in order to maintain the noise at acceptable levels enhancing the quality of life of citizens. Many developed countries have used noise maps to take mitigation actions to control high noise levels at the planning stage of cities by introducing vegetation barriers, wall-type barriers, speed bumps, conditioning up the roads to suite the traffic volume and implementation of engineering designs to produce low level noise emission by vehicles [19]. In this study, a noise map of Galle city, the capital of Southern Province, Sri Lanka, has been produced and noise polluted areas have been identified. The result could be used to control the noise pollution in the city in future developments as an environmental friendly city enhancing the value of the city.

According to WHO guidelines, the maximum recommended day time (6:00 to 18:00) noise level is 55 dB(A). Exceeding this level at day time may cause serious annoyance and speech interference on residence [1]. Indoor guideline values for bedrooms are below 30 dB(A) for continuous noise at night. Exposing to on or above 85 dB(A) noise levels over a period of 8 hours could course serious health effects [5]. National Institute for Occupational Safety and Health (NIOSH - USA) recommends that all workers exposed to noise levels, LAeq , at or above 85 dB(A) for 8h period to undergo audiometric tests frequently. Employers were required to provide personal hearing protectors if they are exposed to 90 dB or greater noise levels ([6], [7]). The threshold of hearing could be lowered due to prolong exposure to heavy noise [8]. Therefore it is very essential to maintain the noise level at busy areas in day and night at acceptable levels. The noise from different sources or activities in a certain area can be mapped quantitatively on A noise map is a graphical representation of the sound level distribution in a given region for a defined period. Noise mapping have been adapted in several urban cities around the world [9]. In order to study the noise level in a given area, a large number of measurements have to be made, which is not an easy task. However, having a certain number of measurements and using the knowledge of propagation of sound,

2. Methodology 2.1 Site selection

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The selected site for the noise mapping under this study was the busiest area of Galle city with the highest traffic conjunction throughout the daytime. Detailed map of selected area is given in figure 1. The area includes the roads A2 (Colombo-Galle-Hambantota-Wellawaya highway), A17 (Galle-Deniyaya-Madampe highway), B128 (Galle Baddegama), B129 (Galle Udugama) and B130 (Galle Wakwella) and number of noise sensitive places (schools, hospitals, religious places, courthouse, public library), historical places, international cricket stadium, shopping complexes, pleasure garden/children parks, rail station, bus stand, public fair, commercial buildings/industries and several government offices.

Expressway (E1) and of most them are passing through this busy area. This selected area includes two heavy traffic circulatory junctions namely TL1 and TL2 here. TL1 is the main interchange of A2 & B130 and TL2 is located at the main entrance of the southern expressway which is controlled by traffic light. Number of tracks of A2 roads between TL1 and TL2 is two but close to the junctions TL1 and TL2 are four and six respectively. It is expected that the road traffic noise level to be highest within the busy area of the noise map. The coordinates of selected area lie from 80° 10.849' to 80° 15.705' East and 6° 01.267' to 6° 04.187' North. The local coordinates

The circled area of the map in figure 1 is the busiest area with the highest traffic circulation in the city. All vehicles enter to the city by A2, A17, B128, B129, B130 and Southern

the railway track in the selected area can be clearly seen in dark red and black colour lines, respectively, in figure 1.

Figure 1: Main roads and railway line in the selected area for noise mapping. (Source: Authors)

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measurements. The analyser was placed on the centre line of the carriageway, 1.2 m above the ground level for road noise measurements. In train traffic noise measurements the analyser was placed at a height of 1.5 m from the ground (to overcome the effect of 0.3 m elevation of the railway track) and 10 m away from the edge of the railway line. As the wind speed could

Field data measurement

Noise measurements were carried out using B&K Type-2250 hand held analyser (IEC 61672-1; 2002 Class1 [20] and the instrument was suitably calibrated using type 4231, B&K sound level calibrator before each

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significantly affects the accuracy of data, UA 1650 90 mm windscreen was used to minimize the wind effect. The grid scale used for measurements is 200 x 200 m2. Atmospheric data such as wind velocity (ms -1), humidity (%) and atmospheric temperature (0C) were measured at the time of measurement using Kestrel 4500 pocket weather tracker. The noise levels created by each category of vehicles were recorded manually in a separate project using a sound level meter in decibels. Hot sunny days were used for measurements. Rainy days were avoided to disregard the additional noise generated due to wet-tyre-road interactions. Garmin eTrex 20 hands held GPS navigator was used to locate the positions.

guidelines given in the elementary library XP S 31-133 (France) in IMMI software [11]. As the road types and noise levels of different sources of European and Asian countries have significant differences [22], IMMI having above features is quite suitable to adapt to situations in Sri Lanka. According to the user requirements, the XP S 31-133 elementary library facilitates with the option to change the initial parameters such as data input (daily traffic volume, dB levels), geometry input (road elevation, road surface type), driving direction input (two-way direction, one-way direction, driving on left or right, etc.), meteorological data input, etc. Apart from that building heights, nature of the surface (reflective or absorptive), number of inhabitancy and number of dwellings has to be set according to the situation.

Noise Measurements were carried out throughout the month of November, 2013, for about 300 locations within the area. Field data was logged in five minute time periods (LAeq, 300s) in automatic mode and measurements were carried out for more than 15 minutes continuously at each location. Noise data were taken on both sides of the road to obtain the average value. For each day, measurements were carried out from 6.00 am to 6.00 pm including busy and relatively calm hours of the day. Terrain height, water sources, land used areas, boundaries, utilities and transport lines etc. were considered for noise map preparation. The necessary Arc GIS data were obtained through the survey department of Sri Lanka.

The interface of XP S 31-133 elementary libraries in IMMI software has three options for input data, which are Q (Number of vehicles in vehicles/h), ADT (Average daily traffic density in vehicles/h) & LAeq/dB(A). Here, Q refers the input data calculated fr Aeq/dB(A) could be either specified directly by the user in "direct" edit mode, or displayed as a value calculated from the traffic data specified by the user in an additional mask in Q mode [11]. Road traffic noise guidelines are built in recommendations of 2003/613/EC [23]. IMMI software has several options to select the input data field, such as sound pressure level, sound power level per unit length, sound power level and indoor level. But in this study the average sound pressure level calculated from the collected data was fed to

2.3 Construction of noise maps Several methods have been used by researchers in preparing noise maps ([10], [21]). In addition to LAeq values, traffic volume, engine power, vehicle speed, type of vehicles, nature of road surface, etc. [11] have also been used in some models in constructing road traffic noise maps. In this study, a well-known software package called powerful package used around the world for noise analysis and for mapping was used. IMMI is intended for carrying out noise prediction calculations based on internationally recognized guidelines [11]. The software contains different algorithms for calculating noise propagation and noise mapping for various noise applications such as road noise, railway noise, aircraft noise, industrial noise etc. The road and railway traffic simulation were adopted with

measuring sound power level of different train engines at the boundary of railway tracks. In case of road noise calculations noise frequencies between 6.5 Hz to 20 kHz in 1/3 octave band were used and for train traffic noise calculation frequency range of 16.5 Hz to 8 kHz in 1/1 octave band were used due to software limitations. A small grid scale (200x200 m2) was used to minimize the possible errors which can be arisen due to buildings and other noise barriers in surface 4


A total area of 42.16 km2 in Galle city in grid scale of 50 m X 50 m was considered for map calculation. Noise level at the ground level and at 40 m height was calculated. The noise level in overall map on ground surface varies between 53.41 dB to 85.07 dB. Average L Aeq in day time (6.00 am to 6.00 pm) of the prepared map is 67.7±5.4 dB(A) at ground level and 33.1± 6.4 dB at 40 m altitude. The detailed noise map at the ground level is shown in figure 2.

layer. Other factors (ground reflection/absorption effects, water sheets, ground, vegetated area, height of terrain etc.) were considered during the map preparation.

3. Results 3.1 Area wide noise level variation in day time

Figure 2: Prepared noise contour map for Galle City in day time. (Source: Authors). The highest noise contours (Light blue colour), 80-85 dB, were laid besides a few sections of A2 road in the busiest part of the city. The lowest day time noise level recorded in this area was 55-60 dB (light green). The percentage areas of different noise contour levels are given in the graph 1. According to the noise map, 68.3% of the total area of 42.16 km2 of Galle city is lying in 65-85 dB noise contours and in 76.3±5.4 % of the total area (suburbs of A2, A17, B41, B109, B128, B129 and B130 roads), the noise level is exceeding the maximum allowed level for residential areas (63 dB(A) of Sri Lanka National Environment Act. No. 47, 1980). Densely populated areas of the city lie within the noise contour of 75-80 dB(A). Throughout this area 33.3% were in 65-70 dB noise contours at day time and it is the largest area noise contour in the map. Therefore this

high noise level has to be controlled to make the city to be more comfortable.

Graph 1: The area percentage of different noise contours levels. 3.2 Core area and other heavily affected areas in the noise map

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This heaviest noise affected area in day time is close to TL 1 as clearly shown in figure 3. Main Bus-stand, railway station, Galle-International Cricket Stadium, Municipal council, District Secretariat complex, some schools, public and pping complexes are inside of this 80-85 dB noise contour. Therefore noise controlling mechanisms has to be implemented for wellbeing of the public those who are frequently exposing to this high noise levels.

75 to 80 through this section of the road is approximately 3300 - 3600 (average: 3450 vehicles per hour) in day time. It is interesting to note that the noise level drops when the number of lanes of the road increases from two to four. The two way track runs between TL1 and the interchange A2-A17, with saturated traffic flow during day time, is the main reason for this highest noise pollution level. It is interesting note the low level of noise along the four lane road to the highway entrance. Therefore, constructing a four lane for this section would be an effective solution to control the noise situation in this section of A2 road.

An enlarged map of heavily noise polluted area of figure 2 is shown in figure 3. There, 80-85 dB high noise level is extending from TL1 to the interchange A2-A17 (near TL2), about 3 km along A2 and then the noise contour dropped to

Figure 3: Enlarged map of highly noise affected area. (Source: Authors) (8.5 %) out of 47 measurements are slightly lower than the predicted values and six measurements points (12.8 %) are slightly higher than the predictions, but these locations are closer to contour boundaries. (This could be expected as the present model has used only averaged LAeq measured along the roads for large area noise mapping). Therefore, the noise map (total map area is 42.16 km2) produced can be confidently use for making judgements on noise pollution in the city.

3.3 Validity of the prediction The validity of predictions of model was tested by comparing the measured values of the noise level at 47 randomly selected locations. Same procedure was followed in data collection as mentioned under methodology. Result is shown in figure 4 on the same noise map which was prepared for the city. Total of 37 measurements out of 47 (78.2%) agreed with the predictions. Four measurements

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Figure 4: Comparison of predictions of the model with measured values at 47 randomly selected locations.

4. Conclusion The diurnal noise variation at the selected area of Galle city (suburb of A2, A17, B128, B129 and B130 roads) exceeds the acceptable level given by the national environment act No 47 in 1980. According to the map prepared, 68.3% of the area in Galle city is spreading 65-85 dB(A) and 76.3±5.4 % of the total area, the noise level is exceeding the maximum allowed level for residential areas (63 dB of Sri Lanka National Environment Act. No. 47, 1980). The widest noise contour, 33.3% of the total area, belongs to 65-70 dB(A) noise contour. The high noise level (80-85 dB) from TL1 to TL2 along A2 road was found to be due to saturated road traffic. The present traffic noise can be reduced by increasing the number of lanes [16]. Therefore, it is proposed to increase the number of lanes of the road from two to four lanes from TL1 to TL2 section of the road in order to reduce the noise level.

regulations and implementation of awareness programs, in order to reduce the noise pollution.

This study shows the importance of preparing noise maps of busy cities in order to study the noise pollution and using them in development and planning of cities. The results also shows that necessity of having noise mitigation actions, such as imposing vegetated barriers, wall-type barriers, develop the road network to suite the traffic volume, introduction of new

[3].

5. Acknowledgement Authors highly acknowledge the financial assistance provided by the Transforming University of Ruhuna to International Status (TURIS) project under Grant No. RU/DVC/Pro 61.

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Special Sessions on Green Technology & Green Energy 5th International Conference on Sustainable Built Environment 2014, Kandy, Sri Lanka, 12th to 15th December 2014 [5].

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