A study indicates that the peak levels of traffic noise are very serious in Karachi. The maximum peak noise values at selected locations exceed 100 decibels (dB), which is very close to the level of 110dB at which hearing impediments might occur.
Dense transportation systems, including roads, railways, and air traffic, characterise the modern urban environment. These systems have caused environmental noise (also known as community noise) pollution. In recent years, road traffic has played a dominant role in causing environmental noise, which can have ill effects on communities.
Traffic noise is known to have both psychosocial and physiological effects on exposed people. The most negative psychosocial effects of traffic noise are annoyance and sleep disturbance. Recent noise studies indicated that traffic noise, as an environmental stressor, increased the activation of the sympathetic nervous and endocrine systems, elevated physiological risk factors such as hypertension and myocardial infarction, and caused serious health problems such as cardiovascular disease.
Karachi is the largest city of Pakistan, and it is experiencing continued rapid growth. The industrialization of Karachi has played an important role in attracting many rural people who are looking for jobs, which has led to rapid growth in recent years. Many manufacturing industries such as steel, textile, chemical, cement, refined petroleum, and processed food are located in Karachi, and it also serves as a national banking and stock exchange hub in Pakistan.
The length of the road network in the city is more than 8,000 kms. Karachi’s roads are not wide enough for heavy vehicles and large traffic volumes and approximately 75 percent of commuters travel from home to workplace using heavy vehicles e.g. buses. For this reason, the city experiences severe traffic jam during commuting time that is an important factor to generate noise and impact residents.
As Pakistan has no noise model to be used for computing noise levels in an automated manner, a field measurement approach was employed to obtain the information regarding the variations of traffic patterns and noise levels in Karachi.
For the study, 308 sites were selected at major intersections to measure the levels of noise exposure and to monitor the volumes of traffic.
Karachi experienced severe traffic congestions around those intersections. The field survey was conducted during morning (06:30–10:30), afternoon (12:00–15:00) and evening (16:30–24:00) for two weeks. The survey period represented normal traffic volume excluding holiday periods including Ramazan, Eid, Ashura, and Christmas. The levels of road traffic noise were collected with a noise dosimeter.
According to the findings of the survey, traffic volumes of morning, afternoon, and evening during weekdays were moderate to very high in the south, central, and east areas of Karachi, where most business and residential sections are located. In particular, weekday evenings showed the highest volume of traffic among the given time periods. High to very high traffic intensities were observed for most (75 percent) of the measurement sites.
The higher volume of vehicles during weekday mornings and evenings is closely associated with commuting patterns. Relatively high volumes of traffic also occurred on weekend evening. Meanwhile, the morning and afternoon traffic volumes of the weekend were lighter than the evenings.
Mornings and evenings showed higher noise levels than afternoons on both weekdays and weekends. According to the WHO guidelines, average noise levels of 50dB can induce moderate annoyance, and those of 55dB can induce serious annoyance. Karachi was found to have average noise levels of over 66dB. These noise levels indicate that the city is exposed to a level of traffic noise that could cause serious annoyance. When considering peak values, similar noise exposure levels were observed at all measurement sites with the approximate average and maximum of 90dB and 100dB, respectively, for both weekdays and weekends. The maximum levels of noise were close to 110dB, which can lead to hearing impairments according to the WHO guidelines.
The old areas of Karachi experienced high noise levels, and most areas of the city were under moderate noise levels during weekday mornings. On the contrary, weekday afternoons showed low and tolerable levels of noise exposure almost everywhere in the city.
On weekday mornings, the zone with the highest noise levels shifted from the old city to the central part, which is the most populated area in Pakistan. This shift was associated with rapid urbanisation and an increased number of vehicles. On the other hand, the noise levels of weekends were lower than those of weekdays. The level of noise exposure was especially low on weekend afternoons. The characteristics of noise levels over time generally matched the patterns of traffic volumes in Karachi and road density. Interestingly, the noise levels of weekend mornings appeared to be relatively high when considering the traffic volume at that time. This might occur because Karachi’s residents like going to low-cost markets on the weekends.
Compared with mode traffic noise, the distribution of peak noise levels was much less related to road density and traffic volume. In fact, almost all of the areas in Karachi were found to have high and very high levels of peak noise at all times The high level of peak noise in the city might be attributed to the behaviour of the Karachi drivers, who have a tendency of using their vehicle horns more frequently than drivers in developed countries The intermittent exposure of peak noise levels was found to have more harmful effects in the human auditory system than constant sound levels, and many noise control policies consider the measurements of noise peaks.
Peak levels of noise, as well as the number of noise events, were shown to be better associated with reactions of annoyance than energy equivalent levels in an aircraft noise study.
Considering peak noise levels, Karachi residents are exposed to noise pollution that could have an adverse effect on their health. The residential areas of Karachi are vulnerable to the exposure of traffic noise without any control barriers.
Pedestrians are mixed with vehicles on the road, so they are directly exposed to peak noise levels. When considering the population density of Karachi, many people are potentially at risk of being exposed to high level of road traffic noise.
Chronic exposure to the peak noise levels could adversely affect the residents of Karachi, so it is urgent to reduce levels of traffic noise in the city. The decision-makers of the city should be aware of the traffic noise levels. A noise abatement plan should be implemented to control and manage noise levels as Karachi becomes more urbanised and industrialised.
Extract from Mehdi MR’s article ‘Spatio-temporal patterns of road traffic noise pollution in Karachi’ published in Environ Int.
