Environ Monit Assess (2009) 148:397–408 DOI 10.1007/s10661-008-0170-4
Assessment of environmental benefits of flyover construction over signalized junctions: a case study S. K. Goyal & Sangita Goel & S. M. Tamhane
Received: 6 June 2007 / Accepted: 14 January 2008 / Published online: 5 February 2008 # Springer Science + Business Media B.V. 2008
Abstract In the present study, the impact of the flyover construction to curb traffic congestion problem has been assessed in terms of traffic decongestion, time saving, fuel saving and emission reduction. A flyover has also been constructed over four signalized junctions in the main commercial area in Nagpur city, India. It was found that about 35% of the total traffic is diverted to the flyover, which results in a reduction of about 32% in the total emission generation. Travel on the flyover resulted in as much as 60–70% saving in time, compared to the travel on the main road, particularly when all the four signals are found to be in the red phase. The loss of fuel for combustion and the associated cost resulting from waiting for the signal to change are also estimated, and these are found to be significant. Keywords Traffic congestion . Traffic junctions . Signals . Emissions . Time delay . Fuel loss
S. K. Goyal (*) : S. Goel : S. M. Tamhane National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur 440 020, India e-mail:
[email protected] e-mail:
[email protected]
Introduction Urban air pollution from road transport is a growing concern for a large number of mega-cities/major urban centers, mainly in developing countries. Road transport is identified as a major source of pollution, contributing 40% to 80% of the total air pollution in such cities. Air pollution has been shown to have serious short and long-term adverse effects on public health. The short-term effects include the irritation of eyes, dizziness, nausea, wheezing, headache, weakness and numbness, chest tightness etc. The long-term effects may lead to respiratory infections, persistent cough, asthma, lung cancer, blood disorders etc. Air pollution may result in the restriction in activity/ reduction in performance, increase in emergency room visits and hospital admissions, and in some cases may lead to death. The effects of air pollution on health are very complex as there are many, different sources and types of pollutants. Poor people, undernourished people, the very young and the very old, and the people with pre-existing respiratory diseases and other health problems are more at risk. The health effects of air pollution are well documented (ESMAP 2004; Anon; WHO 2003, 2004; Godish 2004). With rising income, the cities are expanding their boundaries, both horizontally and vertically, accommodating more and more people and associated activities. As a result, the use of motorized transport
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is expected to increase continuously in the coming years, potentially worsening air quality. The need to tackle the impact of air pollution from transport activities is wide acknowledged in mega-cities/large urban areas, particularly in the developing countries. The increased use of transport activities often results in traffic congestion problems particularly within the city areas such as commercial activity zones. Commuters as well as people residing in the vicinity of such areas are exposed to high levels of air pollution emitted from the vehicles moving in congested areas and/or while waiting for the signals to turn green. Efforts are required to minimize idle time at the traffic signals. Mandavilli et al. (2003) have reported that modern roundabouts can improve traffic flow as well as cut down vehicular emissions and fuel consumption by reducing the vehicle idle time at intersections and thereby creating a positive impact on the environment. The construction of flyovers over congested traffic roads, wherever round-about is not feasible due to space constraint, is considered an effective way of ensuring smooth traffic flow and avoiding unnecessary delays. It also helps in reducing the emissions from vehicles and the unnecessary combustion of fuel (petrol/diesel) while waiting for the signal or traffic to clear. In order to ease the traffic congestion problem, a large number of flyovers have been constructed and are being constructed in major urban centers throughout the world. In this paper, the impact of the construction of a flyover over four signalized junctions in a busy/main market area of Nagpur city has been studied. It is pertinent to mention that, prior to the flyover, there was round-about at two locations (out of four), but with the tremendous increase in traffic activity in the area, those round-about had to be removed. The traffic signals are synchronized, i.e. if a vehicle gets first signal green, by the time it reaches to the second signal, it is also found to be green, and so on, and vice versa. The worst case is that every signal is found in red phase, whenever vehicle reaches the junction. At that time, maximum amount of pollution generation can be expected during idling. The benefits of the construction of the flyover have been estimated in terms of reduction/relief in congestion, reduction in emissions and savings in time delays. The methodology for the collection of the primary data on the traffic movement, estimation of saving in time delay, emission load estimation on a
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2 km stretch of road has been presented in the paper. The consumption of fuel during vehicle in motion and idling of vehicles at signals have also been estimated. The cost associated with the unnecessary loss of fuel during idling has also been estimated and presented in the paper.
Study area details Nagpur is the largest city in central India and the third largest city in the western state of Maharashtra after Mumbai and Pune. Nagpur is situated at 21° 06’′ N latitude and 79° 03’′ E longitude and at a mean altitude of 310 m above sea level. A schematic map of Nagpur city is shown in Fig. 1. With a population of 2.1 million, Nagpur was the Nation's 13th largest urban conglomeration in 2001, and it is estimated to be the 114th largest city in the world in 2006. As much as 99.4% of the population was engaged in non-agricultural activities, attesting to the overwhelmingly urban character of Nagpur city. India’s geographical centre (Zero Mile) is situated here. Nagpur is also famous throughout India as a trade centre for high-quality oranges grown in the region and hence the city is also known as the ‘Orange City'. The estimated population in 2006 is about 2.42 million with a population density of more than 11,000 persons/km2 spread within the Municipal limits of 217.56 km2. A number of important Central and State Government Offices and institutions are located in Nagpur. Industrial Development exists along the fringe areas like Kamptee,
Fig. 1 Schematic map of Nagpur City with study zone marked
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Hingna, Wadi, Khapri, Butibori and Kalmeshwar. Two national highways; NH-6 (Mumbai-Calcutta) and NH-7 (Varanasi-Kanyakumari) and major railway trunk routes (Mumbai, Chennai, Howrah, Delhi) pass through the city. Nagpur is witnessing an economic boom in recent years and is developing fast as a new metro-city. There are about 0.823 million vehicles registered (as on March 2006) in Nagpur district. This is about 9 times more than the vehicles registered in 1985. Of the total vehicle population, more than 75% of the vehicles are registered in Nagpur city. The rate of increase in vehicles was more in post-1995 years, as compared to that of pre-1995 years, and the growth rate is expected to increase at a much faster rate in the coming years. In 2006, the vehicle fleet consisted of approximately 84% 2-wheelers, 8% 4- wheelers, whereas all other types of vehicles making up the remaining 8%. People prefer to use their own vehicles due to insufficient public transport facility and convenience. The present study area lies in the main commercial area (known as Sitabuldi), located almost in the centre of the city. NH7 passes through the study area, between Rahate colony Chowk (RC) T-point (also known as Janta Square) and Gowarikar Chowk (GC) T-point (marked in Fig. 1). There are four signalized junctions named Lokmat Square, Panchsheel Square, Jhansi Rani Square and Variety Square in between the Rahate Colony and Gowarikar Chowk T-points. The total length of the stretch of road is 2 km. On both sides of the road, there are a number of commercial
establishments such as shops, supermarkets, hotels & restaurants, hospitals, cinema hall etc. A city bus stand is also located within this area between Jhansi Rani Square and Variety Square. Beyond the Gowarikar Chowk, the roads lead to other commercial zones, a railway station, an intercity bus stand etc. A schematic diagram of the study area is depicted in Fig. 2. Being in the main market area, the road remains busy with traffic throughout the day, often resulting in traffic congestion and long queues at the signals. This leads to significant delays for vehicles intending to cross the 2 km stretch of road, resulting in significant vehicular pollution. Therefore, a 1.5 km long straight flyover was constructed (without any diversion) to combat the traffic congestion problem and also the time delays caused by the signalized junctions. The benefit of flyover construction in terms of fuel saving, time saving and emission reduction is presented in the subsequent sections.
Methodology Traffic count The traffic movement at both the ends of the flyover was counted manually on an hourly basis for a period of 12 hours, between 9 am and 9 pm. The traffic count locations marked as A, B, C & D on the main
Commercial Activity Zone
A ---> Wardha Road
RC
Main Road LS
Flyover
PS
E--->
