Ali Asghar Alesheikh
Associate Prof., GIS Dept.,
Faculty of Geodesy and Geomatics Eng.,
K.N.Toosi University of Technology,
Mirdamad Cross, Valiasr St., Tehran, Iran
Hossein Alizadeh Golestani Ph.D. Student
Graduate School of the Environment and Energy
slamic Azad University, Tehran, Iran
Gas stations have the potential to impact human environment severely. Even small changes in the location of gas stations can make a big difference to a city environment. Site selection of a gas station has historically focused on reducing the cost of construction and decreasing vehicles travel time. This paper demonstrates how GIS can be used in the site location process to minimize impacts to the environment during construction and from accidental release, as well as to lessen the air/noise pollution and traffic jams.
Variables used as input in this process mainly address direct construction costs and station efficiency once the structure has been completed. Some of the variables examined include: proximity to population centers, distance from neighboring stations, the easements of using existing utility, and the magnitudes of environmental pollution parameters.
As a case study, Mashhad the capital of Khorassan province in Iran has been selected. Spatial variables together with attribute information are gathered and uploaded to a commercial GIS software. Results demonstrated that locating gas stations in the city centre or around the commercial zones increase the number of trips as well as traffic jams. District one presents the best configuration while district seven is the worst place for locating gas stations. With regards to the environmental parameters Districts 3 and 4 has a high potential to generate pollutions. In contrary, district one has the least effect on the city pollution.
The increase of urban population and the growth of the number of cars and plying generate various kinds of environmental pollutions, such as air pollution, and noise pollution in large cities and inflict a lot of costs by causing heavy traffic and wasting people’s time. A considerable amount of cars fuel is wasted due to the long urban paths and unnecessary trips. The fuel emits dangerous pollutants as well. Air pollution affects the environment from different aspects, such as landscapes, building’s appearance, plant biomass, water quality and soil and residential health (Breslow et al., 2002; Harrison, 1999). Gas stations are among the places that residents refer to repetitiously. Considering the number of cars and urban population, distributing gas station sites can be effective in shortening urban trip paths and reducing the emission of different pollutants. Examining this matter for Mashhad as the most populated city of Iran after Tehran is of vital importance and it’s necessity is felt more than before. Geospatial Information Systems (GIS) provide the appropriate tools for analyzing the effective factors on environmental pollution based on spatial data and non-spatial data.
Mashhad city is the center of Khorasan Razavi Province located in the North East of Iran and at a distance of 965 km from Tehran. The city extends from 59 degrees and 15 minutes to 60 degrees and 36 minutes of geographic longitude and from 35 degrees and 43 minutes to 37 degrees and 8 minutes of geographic latitude.
Mashhad is the most populated city of Iran after Tehran, and is known as a religious city. The transportation and movements of residents is mainly done by private cars, although public buses and taxies are also functioning. Mashhad has 12 municipal regions.
The working method is mostly made up of three stages. In the first step, requirement analysis is done, in which the needed spatial and attribute data are identified. The information is gathered and entered to ArcView GIS software. In the second stage the input data is analyzed and the required information layers are made. In the last stage by examining the output information from the second stage conclusions and necessary suggestions are made.
The basic data used in this research are:
- the digital topographic maps of Mashhad that contains 25 information layers.
- the information related to transportation and urban traffic
ArcView software is then used to generate:
- Urban Cadastral layer in which the locations of gas stations are specified and their attributes is linked to each spatial feature.
- Buildings information layer containing the polygons of urban regional divisions and their attributes containing the number of cars, Gas Stations, and populations.
- the information layer containing the regions’ centers.
Spatial Analyst extension of ArcView is used to compute the distance of each region center to gas stations. Considering the stay time of each vehicle on it’s path, the potential of a region in causing pollution is then determined.
Results and Discusions:
The sum of the distances of the center of each region from gas stations is calculated. The results show that the Seventh region is most distant from gas stations. In other words, the residents of this region have the least access to gas stations. On the other side, the first region has the most access to gas stations. So we can conclude that in equal conditions and by assuming the fact that one of the targets of urban traveling is to get to a gas station, the settlers of the seventh region must travel to longest distance, so they will use more fuel to reach the target.
Compare to 5th ,6th ,8th ,and 1st region, the Seventh municipality region has the most number of cars. So we can say that this region has a fairly great part in air pollution, and by foreseeing building gas stations in this region we can repel the pollution problem.
The following figure presents the sum of the distances of each region’s center from gas stations.
Figure 1. The sum of distances to gas stations for the 12 municipality region
Figure 2 shows Mashhad city, together with gas stations locations and each region’s centers. The colors present the sum of distances to gas stations for each region.
Figure 2: Study area, and the sum of distances to gas stations for each region
Considering the population, the 3rd region is the most populated one while taking into account the population density, it has the second place. So we can conclude that the amount of traffic is more in comparison to other regions. On the other hand, access to gas stations is higher than 1st , 2nd ,8th and region 12 and the sum of distances from this region to gas stations is more so the potential of causing pollution in this region is high. It is suitable to consider another gas station in this region to reduce the stay time of vehicles in this high traffic region. Doing so, will save fuel cost and prevent pollution. Figure 3 presents the regions ranking based on the population access to gas stations.
Considering population density, the 4th region is the densest region. This region, after region 3, has the most number of cars and people settled. So we can conclude that the region has high amount of traffic. Considering access to gas stations, this region has the worst access after region 7, so heavy traffic and being far from gas stations has increased fuel use and caused pollution. Figure 4 presents the regions ranking based on the population density and access to gas stations.
Figure 3: The regions ranking based on the population access to gas stations
Figure 4: The regions ranking based on the population density and access to gas stations
Considering the number of cars the 3rd region has the most cars and the 12 region has the least amount of cars. On the other side, in region 12 and because of the existence of the holy shrine and commercial centers has a high amount of traffic and has the best access to gas stations. So In this region there is no need to build a new gas station and building gas stations increases traffic and as a result increases pollution in this region.
Conclusions and Recommendations:
The GIS knowledge and it’s practical soft wares can be useful in analyzing and finding out how to reduce pollutants in the city. The results of the examinations show that we can specify the potential of causing pollution for each region in comparison to other regions. In this examination by focusing on the site selection method of gas stations and their impact on causing pollution, high potential regions were specified. The results showed that the regions 3 and 4 (because of high population and high population density and region 7 because of poor access to gas stations) have the highest pollution potential in comparison to other regions and region 1 has the least part in causing pollution. It is suggested to study this subject by considering other factors such as architecture and road building methods in regions and compare the results with this research.
The results can be useful for decision makers in Mashhad city. It must be mentioned that the presented strategy is a tool to help decision makers, it is not the decision itself.
- Breslow, L.; Goldstein, B.; Green, L.; Keck, W.; Last, J.; McGinnis, M., (2002). Encyclopedia of Public Health., Macmillan Publication, USA, 1480 p.
- Harrison R., (1999). Understanding our Environment., Royal Society Chemistry, UK, 444 p.