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Traffic noise level as a guide for town-planning
Applied Acoustics 16 (1983) 139-146
Traffic Noise Level as a Guide for Town-planning O. A b d e l Alim, T. Y. El-Reedy a n d A. A b o u - E 1 - H a s s a n Faculty of Engineering, Alexandria University, Alexandria (Egypt) (Received: 24 June, 1982) S UMMA R Y The aim of th& paper is to prove the validity of a mathematical model which gives the relationship between traffic noise level and traffic composition. This model was used at five different sites, representing different land uses, in Alexandria, Egypt. The paper gives various examples illustrating the fact that the equivalent noise level will be considerably reduced by changing the traffic composition. This shows that the town-planner can use various strategies to change the traffic composition in order to achieve quieter city environments.
INTRODUCTION Recent research 1 has proposed the noise level in built-up areas as a guideline for town-planning but a definite relationship between this level and the volume (or composition) of traffic in such areas has not been established. A detailed study on the cost and benefit of transportation noise has been carried out 2 but no relationship between noise abatement and town-planning was established. References3 and 4 give some descriptive, rather than objective, steps for town-planning where the population can be provided with adequate safeguards against harmful noise effects. Heermrood s tackles the problem of noise level and townplanning in its broader sense when he states that: 'the main solution lies in the decrease of motorised traffic' without, however, emphasising his statement with an objective example. 139 Applied Acoustics 0003-682X/83/0016-0139/$03.00 © Applied Science Publishers Ltd, England, 1983. Printed in Great Britain
140
O. Abdel Alim, T. Y. El-Reedy, A. Abou-El-Hassan
The authors presented, in reference 6, a relationship between traffic volume, traffic composition and the equivalent noise level, based on field measurements at a particular site in Alexandria, Egypt. This paper investigates the validity of the model at five other sites in Alexandria representing different land uses and discusses different ways of improving environmental conditions at these sites.
SITE DESCRI PTION In order to test the model for different land uses, various types of site were selected--an industrial area, a downtown area, a residential area and an area with potential for city extension development. A brief description of each site is given below. Industrial area
The site chosen to represent the industrial land use is located in EI-Maks, a major industrial suburb to the west of Alexandria. The location for field measurement was along E1-Maks Street. The road is a multi-lane divided highway, 25 m wide, accommodating 550 vehicles an hour on the inside lane during the peak traffic hour, of which 30 per cent are trucks, truck/ trailer combinations and pick-up trucks. D o w n t o w n area
Two sites were selected to represent downtown areas. The first was along Saad Zaghlool Street, a one-way street, 15 m wide, with its inside lane carrying 500 vehicles during the peak hour. It is a main shopping street with heavy pedestrian movement served by two sidewalks on either side of the road, each 3-5 m wide. The second site was chosen along Sezostris Street, a two-lane road 12 m wide with mainly office buildings on both sides. The traffic volume measured during the morning peak hour in the direction of the heaviest flow was found to be 500 vehicles. No commercial vehicles or buses are allowed at either site.
Traffic noise level as a guide for town-planning
141
Residential area
Two sites were selected to represent residential land use. The first was located along Horreya Avenue, a main arterial road running in an eastwest direction. The road is a single carriageway, 15 m wide, with a solid white stripe along its centre separating the opposite traffic flows. The traffic flowing along the road is a mixture of private cars, taxis, minibuses, buses and a few trucks. The traffic volume flowing in an eastbound direction averages 650 vehicles an hour along the inside lane. The second location selected was E1-Rassafa, a major road in the old district of Moharrem Bey. It is a two-way highway, 15 m wide with an observed flow of 330 vehicles during the morning peak hour, travelling along the inside lane. Future extension of the city of Alexandria
This site is located along the Delta express road at the point where it crosses the district of Somoha at the southern entrance of the city. Residential tower blocks are under construction in this area which represents the future extension of the city. The Delta express road, along which measurements were recorded, is a four-lane divided highway, 15 m wide, with an average volume of 800 vehicles an hour travelling along the inside lane, of which 225 are a mixture of trucks, truck/trailers and pickup trucks.
FIELD M E A S U R E M E N T S
Simultaneous observations of traffic composition and noise level in dB(A) were recorded for ten intervals at the above-mentioned sites, each interval being 10-min long. The average time between successive observations was 3"5 s. Noise level was measured using a B & K precision sound level meter, Type 2215. The volume of traffic was measured and classified manually for the inside lane of the different roads, nearest to the sound level meter.
O. Abdel Alim, T. Y. El-Reedy, A. .4bou-El-Hassan
142
RESULTS The authors 6 previously presented the following model to calculate the equivalent noise level (Leq), given a certain traffic composition: I
1
10~Leq/l°) = ~-~
(ti/T). a i . 10tLi/l°) + A
i=1
Where: Leq
=
Equivalent noise level in dB(A).
tilT = Percentage of the total observation time, T, during which ai = Li = n=
A=
the noise is attributed to the traffic component (i). Passenger car equivalent factor for the traffic component (i). Noise level in dB(A) for each traffic component (i). Number of vehicle types under consideration. These are: private cars, private buses, Ward public buses (a special model of public transport bus that proved to be significantly noisier than any other bus), trucks, minibuses, pick-up trucks and motor cycles. Residual equivalent energy due to sources other than the above-mentioned vehicle types. It consists of heavy vehicles travelling in the opposite direction and horn and background noises.
= ~ , tJT. aj. 10tL/lO) j=l
Where:
tJT = Percentage of the total observation, T, during which the noise level of source (j) is observed. aj = Weighting factor equal to 1.0 for the horn and background noises and 2.5 for the heavy vehicles travelling in the opposite directions. Lj = Noise level of source (j).
Table 1 shows the modelled value of the equivalent noise (Leq1) together with the observed equivalent noise level (Leq2) calculated from the field measurements according to the formula given in reference 7. Table 2 shows the modelled noise levels at the different sites if certain restrictions are introduced to improve environmental conditions. In this Table Leqll is the equivalent noise level in the absence of horns. Leql z is
89.3
88.9
Observed noise level Leq 2
Interval a
89-9
90.0
Interval b
Industrial areas (El- Maks)
Modelled noise level LeqI
Equivalent noise level
81-4
82.8 78.1
80.0
(Saad Zakhlool) Interval Interval a b
84.4
84-2
(Sezostris)
Downtown areas
88"0
87-1
87.0
86'3
86-4
84.4
(El-Rassafa)
Residential areas
(Horreya Avenue) Interval Interval a b
Site
Modelled and Observed Equivalent Noise Level for Different Land Uses in dB(A)
TABLE 1
85-8
85"6
Interval a
85.0
85-9
Interval b
The Delta express road, Somoha
87"1
84.6
Leqll
Interval a
teql4
--
85-6
87.6
Interval b
Industrial areas (El-Maks)
Leql2
Modelled noise level
Equivalent noise level
Zeql3
TABLE 2
73.6
---
--
74.2
(Saad Zaghlool) Interval Interval a b
--
.
73.2
(Sezostris)
Downtown areas
.
80-2
83.6
85.1 .
81 "6
83-7
84.3 .
76.7
79.9
80.0 .
(E. Rassafa)
Residential areas
(Horreya Avenue) Interval Interval a b
Site
--
78.8
85.6
Interval a
--
77.4
84.4
Interval b
The Delta express road, Somoha
Modelled Equivalent N o i s e Level with Different L i m i t a t i o n s to I m p r o v e E n v i r o n m e n t a l C o n d i t i o n s in dB(A)
t~
5,
:x
Traffic noise level as a guide for town-planning
145
the equivalent noise level in the absence of horns together with limiting the commercial vehicles to 10 per cent in the industrial area; Leq13is the equivalent noise level in the absence of horns and trucks in the residential area and Leq14is the equivalent noise level in the absence of horns, trucks and noisy buses in the residential area.
D I S C U S S I O N OF R E S U L T S (a) A statistical analysis was carried out on the difference between the measured noise level (Leq2) and the modelled noise level (Leql). This analysis showed that the mean of the differences is equal to - 0 . 0 6 dB(A) with a standard deviation of 1.15 dB(A). This difference was shown to be insignificant at the 95 per cent level of significance. In other words, considering the 95 per cent level of significance, the difference between the measured noise level and the modelled noise level is between - 0 . 9 2 dB(A) and - 1.04 dB(A). This indicates that the model is valid for different land uses. (b) In the absence of horns, the equivalent noise level decreased at all sites except for one interval along the Delta express road. The maximum reductions of 9-2dB(A) and 11 dB(A) occurred in the downtown area, Saad Zaghlool Street and Sezostris Street, respectively, where there are no busesior commercial vehicles. With larger sidewalks, pedestrians will not walk in the street and motorists will not abuse the use of horns. (c) A considerable decrease of 4-7 and 4-4 dB(A) in the equivalent noise level was achieved in the EI-Maks industrial area during the two intervals of measurement when the horns were omitted and commercial vehicles were limited to l0 per cent. (d) Omitting the effect of horns and trucks when modelling the equivalent noise level in residential areas improved the environmental condition. Leq was reduced by 2 dB(A) in Horreya Avenue, by 4.4 dB(A) in E1-Rassafa and by 8.5 dB(A) during one interval in Somoha, along the Delta,express road. This discrepancy in the results is attributed to the high percentage of commercial vehicles in Somoha when compared with the other two sites as the Delta express road is a main highway that links Alexandria'to the rest of the country. (e) Omitting the Ward buses from residential areas gave a further reduction in the equivalent noise level varying between 2.1 dB(A) and 3.2 dB(A) at Horreya Avenue and E1-Rassafa, respectively. The reduction
146
o. Abdel Alim, T. Y. El-Reedy, A. Abou-EI-Hassan
is mainly dependent upon the number of these buses presently in operation at each site. (f) The various strategies discussed above to improve the environmental conditions could be more efficiently looked at as an optimisation problem. In that case, the model would preferably be rewritten as follows: n
M = ~ ' (ti/T). (ai)Mi + A I
d
i=1
Where: M = 10 tLeq/l°) and M i = 10 tz'/l°). This is a linear function between M and the variables ti, i = 1. . . . . n that can be looked at as an objective function. With proper constraints one can minimise M for a certain combination of the variables t~, a combination that would vary from site to site. For instance, in a residential area, passenger cars and buses prevail, but in what proportion so that M is minimised without depriving passengers of a comfortable mode of transport? In an industrial area where pick-up trucks, single unit trucks and truck/trailer combinations prevail, what proportion of each of these vehicle types should be chosen to minimise M without affecting the total fleet capacity? This would undoubtedly help a town-planner in planning quieter cities. The details and full elaboration of this linear programming problem will be the subject of another paper. REFERENCES 1. F. Kranendok and L. Nijis, The prediction of noise levels in built up areas and acoustical guidance for town-planning, Proceedings of Inter-Noise '80, Miami, 1980, pp. 899-902. 2. US EPA, Noise Abatement: Policy Alternatives for Transportation; National Academy of Science, Washington, DC, 1977. 3. L. H. Schaudinischky, Sound, man and building, Applied Science Publishers Ltd, London, 1976, pp. 325-6. 4. D.J. Croome, Noise, buildings andpeople, Pergamon Press, New York, 1977, 284-5. 5. J. C. Heermrood, Town-planning and noise, Proceedings of Inter-Noise '81, Amsterdam, 1981, pp. 621-6. 6. O. Abdel Alim, T. El-Reedy and A. Abou-Elhassan, Measurements of traffic volume and traffic noise. Proceedings of Inter-Noise '81, Amsterdam, 1981, pp. 533-6. 7. L. L. Beranek, Noise and vibration control, McGraw-Hill, New York, 1971, pp. 568-9.
Traffic Noise Level as a Guide for Town-planning O. A b d e l Alim, T. Y. El-Reedy a n d A. A b o u - E 1 - H a s s a n Faculty of Engineering, Alexandria University, Alexandria (Egypt) (Received: 24 June, 1982) S UMMA R Y The aim of th& paper is to prove the validity of a mathematical model which gives the relationship between traffic noise level and traffic composition. This model was used at five different sites, representing different land uses, in Alexandria, Egypt. The paper gives various examples illustrating the fact that the equivalent noise level will be considerably reduced by changing the traffic composition. This shows that the town-planner can use various strategies to change the traffic composition in order to achieve quieter city environments.
INTRODUCTION Recent research 1 has proposed the noise level in built-up areas as a guideline for town-planning but a definite relationship between this level and the volume (or composition) of traffic in such areas has not been established. A detailed study on the cost and benefit of transportation noise has been carried out 2 but no relationship between noise abatement and town-planning was established. References3 and 4 give some descriptive, rather than objective, steps for town-planning where the population can be provided with adequate safeguards against harmful noise effects. Heermrood s tackles the problem of noise level and townplanning in its broader sense when he states that: 'the main solution lies in the decrease of motorised traffic' without, however, emphasising his statement with an objective example. 139 Applied Acoustics 0003-682X/83/0016-0139/$03.00 © Applied Science Publishers Ltd, England, 1983. Printed in Great Britain
140
O. Abdel Alim, T. Y. El-Reedy, A. Abou-El-Hassan
The authors presented, in reference 6, a relationship between traffic volume, traffic composition and the equivalent noise level, based on field measurements at a particular site in Alexandria, Egypt. This paper investigates the validity of the model at five other sites in Alexandria representing different land uses and discusses different ways of improving environmental conditions at these sites.
SITE DESCRI PTION In order to test the model for different land uses, various types of site were selected--an industrial area, a downtown area, a residential area and an area with potential for city extension development. A brief description of each site is given below. Industrial area
The site chosen to represent the industrial land use is located in EI-Maks, a major industrial suburb to the west of Alexandria. The location for field measurement was along E1-Maks Street. The road is a multi-lane divided highway, 25 m wide, accommodating 550 vehicles an hour on the inside lane during the peak traffic hour, of which 30 per cent are trucks, truck/ trailer combinations and pick-up trucks. D o w n t o w n area
Two sites were selected to represent downtown areas. The first was along Saad Zaghlool Street, a one-way street, 15 m wide, with its inside lane carrying 500 vehicles during the peak hour. It is a main shopping street with heavy pedestrian movement served by two sidewalks on either side of the road, each 3-5 m wide. The second site was chosen along Sezostris Street, a two-lane road 12 m wide with mainly office buildings on both sides. The traffic volume measured during the morning peak hour in the direction of the heaviest flow was found to be 500 vehicles. No commercial vehicles or buses are allowed at either site.
Traffic noise level as a guide for town-planning
141
Residential area
Two sites were selected to represent residential land use. The first was located along Horreya Avenue, a main arterial road running in an eastwest direction. The road is a single carriageway, 15 m wide, with a solid white stripe along its centre separating the opposite traffic flows. The traffic flowing along the road is a mixture of private cars, taxis, minibuses, buses and a few trucks. The traffic volume flowing in an eastbound direction averages 650 vehicles an hour along the inside lane. The second location selected was E1-Rassafa, a major road in the old district of Moharrem Bey. It is a two-way highway, 15 m wide with an observed flow of 330 vehicles during the morning peak hour, travelling along the inside lane. Future extension of the city of Alexandria
This site is located along the Delta express road at the point where it crosses the district of Somoha at the southern entrance of the city. Residential tower blocks are under construction in this area which represents the future extension of the city. The Delta express road, along which measurements were recorded, is a four-lane divided highway, 15 m wide, with an average volume of 800 vehicles an hour travelling along the inside lane, of which 225 are a mixture of trucks, truck/trailers and pickup trucks.
FIELD M E A S U R E M E N T S
Simultaneous observations of traffic composition and noise level in dB(A) were recorded for ten intervals at the above-mentioned sites, each interval being 10-min long. The average time between successive observations was 3"5 s. Noise level was measured using a B & K precision sound level meter, Type 2215. The volume of traffic was measured and classified manually for the inside lane of the different roads, nearest to the sound level meter.
O. Abdel Alim, T. Y. El-Reedy, A. .4bou-El-Hassan
142
RESULTS The authors 6 previously presented the following model to calculate the equivalent noise level (Leq), given a certain traffic composition: I
1
10~Leq/l°) = ~-~
(ti/T). a i . 10tLi/l°) + A
i=1
Where: Leq
=
Equivalent noise level in dB(A).
tilT = Percentage of the total observation time, T, during which ai = Li = n=
A=
the noise is attributed to the traffic component (i). Passenger car equivalent factor for the traffic component (i). Noise level in dB(A) for each traffic component (i). Number of vehicle types under consideration. These are: private cars, private buses, Ward public buses (a special model of public transport bus that proved to be significantly noisier than any other bus), trucks, minibuses, pick-up trucks and motor cycles. Residual equivalent energy due to sources other than the above-mentioned vehicle types. It consists of heavy vehicles travelling in the opposite direction and horn and background noises.
= ~ , tJT. aj. 10tL/lO) j=l
Where:
tJT = Percentage of the total observation, T, during which the noise level of source (j) is observed. aj = Weighting factor equal to 1.0 for the horn and background noises and 2.5 for the heavy vehicles travelling in the opposite directions. Lj = Noise level of source (j).
Table 1 shows the modelled value of the equivalent noise (Leq1) together with the observed equivalent noise level (Leq2) calculated from the field measurements according to the formula given in reference 7. Table 2 shows the modelled noise levels at the different sites if certain restrictions are introduced to improve environmental conditions. In this Table Leqll is the equivalent noise level in the absence of horns. Leql z is
89.3
88.9
Observed noise level Leq 2
Interval a
89-9
90.0
Interval b
Industrial areas (El- Maks)
Modelled noise level LeqI
Equivalent noise level
81-4
82.8 78.1
80.0
(Saad Zakhlool) Interval Interval a b
84.4
84-2
(Sezostris)
Downtown areas
88"0
87-1
87.0
86'3
86-4
84.4
(El-Rassafa)
Residential areas
(Horreya Avenue) Interval Interval a b
Site
Modelled and Observed Equivalent Noise Level for Different Land Uses in dB(A)
TABLE 1
85-8
85"6
Interval a
85.0
85-9
Interval b
The Delta express road, Somoha
87"1
84.6
Leqll
Interval a
teql4
--
85-6
87.6
Interval b
Industrial areas (El-Maks)
Leql2
Modelled noise level
Equivalent noise level
Zeql3
TABLE 2
73.6
---
--
74.2
(Saad Zaghlool) Interval Interval a b
--
.
73.2
(Sezostris)
Downtown areas
.
80-2
83.6
85.1 .
81 "6
83-7
84.3 .
76.7
79.9
80.0 .
(E. Rassafa)
Residential areas
(Horreya Avenue) Interval Interval a b
Site
--
78.8
85.6
Interval a
--
77.4
84.4
Interval b
The Delta express road, Somoha
Modelled Equivalent N o i s e Level with Different L i m i t a t i o n s to I m p r o v e E n v i r o n m e n t a l C o n d i t i o n s in dB(A)
t~
5,
:x
Traffic noise level as a guide for town-planning
145
the equivalent noise level in the absence of horns together with limiting the commercial vehicles to 10 per cent in the industrial area; Leq13is the equivalent noise level in the absence of horns and trucks in the residential area and Leq14is the equivalent noise level in the absence of horns, trucks and noisy buses in the residential area.
D I S C U S S I O N OF R E S U L T S (a) A statistical analysis was carried out on the difference between the measured noise level (Leq2) and the modelled noise level (Leql). This analysis showed that the mean of the differences is equal to - 0 . 0 6 dB(A) with a standard deviation of 1.15 dB(A). This difference was shown to be insignificant at the 95 per cent level of significance. In other words, considering the 95 per cent level of significance, the difference between the measured noise level and the modelled noise level is between - 0 . 9 2 dB(A) and - 1.04 dB(A). This indicates that the model is valid for different land uses. (b) In the absence of horns, the equivalent noise level decreased at all sites except for one interval along the Delta express road. The maximum reductions of 9-2dB(A) and 11 dB(A) occurred in the downtown area, Saad Zaghlool Street and Sezostris Street, respectively, where there are no busesior commercial vehicles. With larger sidewalks, pedestrians will not walk in the street and motorists will not abuse the use of horns. (c) A considerable decrease of 4-7 and 4-4 dB(A) in the equivalent noise level was achieved in the EI-Maks industrial area during the two intervals of measurement when the horns were omitted and commercial vehicles were limited to l0 per cent. (d) Omitting the effect of horns and trucks when modelling the equivalent noise level in residential areas improved the environmental condition. Leq was reduced by 2 dB(A) in Horreya Avenue, by 4.4 dB(A) in E1-Rassafa and by 8.5 dB(A) during one interval in Somoha, along the Delta,express road. This discrepancy in the results is attributed to the high percentage of commercial vehicles in Somoha when compared with the other two sites as the Delta express road is a main highway that links Alexandria'to the rest of the country. (e) Omitting the Ward buses from residential areas gave a further reduction in the equivalent noise level varying between 2.1 dB(A) and 3.2 dB(A) at Horreya Avenue and E1-Rassafa, respectively. The reduction
146
o. Abdel Alim, T. Y. El-Reedy, A. Abou-EI-Hassan
is mainly dependent upon the number of these buses presently in operation at each site. (f) The various strategies discussed above to improve the environmental conditions could be more efficiently looked at as an optimisation problem. In that case, the model would preferably be rewritten as follows: n
M = ~ ' (ti/T). (ai)Mi + A I
d
i=1
Where: M = 10 tLeq/l°) and M i = 10 tz'/l°). This is a linear function between M and the variables ti, i = 1. . . . . n that can be looked at as an objective function. With proper constraints one can minimise M for a certain combination of the variables t~, a combination that would vary from site to site. For instance, in a residential area, passenger cars and buses prevail, but in what proportion so that M is minimised without depriving passengers of a comfortable mode of transport? In an industrial area where pick-up trucks, single unit trucks and truck/trailer combinations prevail, what proportion of each of these vehicle types should be chosen to minimise M without affecting the total fleet capacity? This would undoubtedly help a town-planner in planning quieter cities. The details and full elaboration of this linear programming problem will be the subject of another paper. REFERENCES 1. F. Kranendok and L. Nijis, The prediction of noise levels in built up areas and acoustical guidance for town-planning, Proceedings of Inter-Noise '80, Miami, 1980, pp. 899-902. 2. US EPA, Noise Abatement: Policy Alternatives for Transportation; National Academy of Science, Washington, DC, 1977. 3. L. H. Schaudinischky, Sound, man and building, Applied Science Publishers Ltd, London, 1976, pp. 325-6. 4. D.J. Croome, Noise, buildings andpeople, Pergamon Press, New York, 1977, 284-5. 5. J. C. Heermrood, Town-planning and noise, Proceedings of Inter-Noise '81, Amsterdam, 1981, pp. 621-6. 6. O. Abdel Alim, T. El-Reedy and A. Abou-Elhassan, Measurements of traffic volume and traffic noise. Proceedings of Inter-Noise '81, Amsterdam, 1981, pp. 533-6. 7. L. L. Beranek, Noise and vibration control, McGraw-Hill, New York, 1971, pp. 568-9.