چكيده لاتين :
Transportation and traffic problems are one of the most tangible and critical issues in metropolitans such as Tehran, Iran. In addition to an increase in fuel consumption, lack of integrated and efficient transport system in large cities attributes to other problems such as an increase in number of automobiles, the intra-city travel time, car accidents with financial and body injuries, residencesʹ discontent, various types of pollution, inefficient use of time, and finally an accelerated destruction of environmental recourses.
This research aims to determine the effects of various transportation methods in Tehran on the environmental resources (2007), taking particular fuel consumption into consideration. From these data, a possible combination of transportation systems will be suggested which can reduce fuel consumption and improve environmental quality in Tehran in the future (2026). The methodology used here is based on the ecological footprint (EF) approach developed by Rees and Wackernagel (1996).
The EF represents the amount of natural goods and services consumed or demanded by people. This is equivalent to the land surface or amount of water which has been used to either meet the consumption needs of the community, or absorb their production waste. Unlike the conventional methods of environmental impact assessment (EIA) which are essentially qualitative decision making methods where the environmental impact is determined by using the proportional ranges of+10 to -10, the EF approach applies real, measurable criteria for environmental decision makings, i.e. "land". This feature makes EF a global comparative measure of environmental quality. A large value of EF indicates high level of damage to the environment caused by human activities while small EF shows low level of environmental destruction. Therefore by converting all aspects of consumption to the common measure of "land", it is possible to evaluate and compare the use of resources at large or even small urban scales, e.g. neighborhoods.
The area of study in this research includes 22 urban regions of Tehran with 7,962,201 people living in 74077.7 hectares (107 persons per hectare) as of 2007. The primarily methods of transportation includes buses, minibuses, taxis, subway and personal vehicles.
At first step, the number of transportation vehicles, the daily rate of people moved by each device and the daily fuel consumption per person for each vehicle was estimated. Then, the equal area of land per capita, which has been used to produce daily consumption of each vehicle within the urban transport system in Tehran, was calculated. In other words, the daily rate of fuel consumption and the corresponding land area (m2 / ha), are calculated as the ecological footprints (EF) of each user of any vehicles within the city of Tehran. Finally, using statistical methods and also the predictions of population of Tehran in 2026, the ideal combination of various transportation techniques, which will cause minimum destruction to the environmental resources, was estimated.
Assuming that "l hectare of land absorbs 1.8 hectares of carbon", the per capita ecological footprints (EF) of each vehicle in Tehran (in 2007) is calculated as 0.39 m2 for bus, 0.67 m2 for minibus, 2.2 m2 for taxi, 1.9 m2 for Motorcycle, 4.2 m2 for personal cars and 0.003 m2 for subway.
Tablel: Calculated per capita ecological footprint (EF) in each vehicle in the city of Tehran in 2007
vehicles Bus Minibus Taxi Motorcycle Personal car Subway
Per capita ecological footprint (m2) 0.39 0.67 2.2 1.9 4.2 0.003
The results show that the daily use of subway, with 0.003 m2 land for producing the consumed fuel, produces the least amount of undesirable effects on the environmental resources and therefore can be considered as the most compatible vehicle to the environment. Personal cars, on the other hand, make the most destructive effects on the environmental resources. In other words, transportation of each person by bus, minibus, taxi, motorcycle and personal car are respectively 130, 223, and 733, 633 and 1400 times more harmful to the environment than subway.
Now, in order to obtain the percentage of passengers of various vehicles that will result in minimum damage to the environmental resources, subway (being the most environment-friendly method of transportation) will be used as the basis of analysis, i.e. number of equivalent passengers in each vehicle is calculated in comparison with the subway. The results of such analysis show that the share (in percentage) of each vehicle (based on the equivalent passenger numbers in comparison with subway) equals to 0.76, 0.45, 0.45, 0.14, 0.16 and 0.071 for bus, minibus, taxi, motorcycle and personal cars respectively. The share of subway is estimated as 98.4 percent. This suggests that in order to minimize the amount of damage and destruction to the environment, for every 98,419 person travelled by subway, there has to be an equivalent of 760 persons by bus, 450 by minibus, 140 by taxi, 160 by motorcycles and finally 71 by personal vehicles.
Assuming that in 2026, the estimated population of Tehran increases by 10,000,000 (based on the growth rate of 1.57 percent, in order to minimize the damages to the environmental resources, the daily share of each transportation vehicle is predicted as 76,000 people for bus, 45,000 for minibus, 14,000 for taxi, 16,000 motorcycle, 7,100 for personal cars and finally 9,841,900 people for urban subway.
Table 2: Predict the daily share of each transportation vehicle that will result in minimum damage to the
environmental resources in 2026
Type of vehicle Number of passengers (person)
bus 76000
minibus 45000
taxi 14000
motorcycle 16000
personal cars 7100
subway 9841900 It is noteworthy that the predicated shares of each vehicle are the ideal values for producing minimum damages to the environmental resources. Consequently, deviation from these values will result in more severe destruction of environment, the extent of which depends on the magnitude of the deviation.
