Transport sector accounts for nearly one-quarter of global energy-related CO2 emissions. In India, the transportation segment is one of the major anthropic contributors to the environment of greenhouse gases (GHGs) and other contaminants which have significant adverse effects on human health. The transport industry contributes greatly to global emissions of carbon dioxide, which absorbs 20% of the total fossil energy used and generated 23% to all energy-related CO2 emissions in 2012. ( IEA, 2014 ). Looking at the increasing trends of motorization in India, there are low chances that carbon emissions will reduce in near future. It can be done if Carbon studies are done in cities, which can help in taking the necessary actions. Therefore, this paper will focus on the indicators which are necessary to make carbon studies in Indian cities and therefore, some strategies and recommendations are also suggested which can help to minimize the impact on environment.
Key-words: Low carbon mobility, green transport, Carbon emissions, mobility indicators
In recent years, increase in the use of vehicle has led to increase in congestion, accidents, and local level air pollution. If this trend continues, the situation will deteriorate even further. By aligning development and climate goals, India can make its transport growth more sustainable. The National Action Plan for Climatic Changes (NAPCC) outlines a combination of measures that can reduce transport CO2 emissions, which includes increase in public transport, alternative fuel use, enhanced vehicle energy efficiency, and other initiatives. These are organized in eight National Missions. Many low-carbon mobility solutions will help achieve economic, environmental and social goals which can also help to improve cities 'carrying capacity. This include increasing mobility access, reducing road congestion in parking areas. It also encourages economic growth, improves public health and safety, and reduces emissions from air and noise. Transport is accountable for fatalities, road injury, vibration, noise and congestion at the local scale (Santos et al., 2010). At the national level, transport is responsible for producing numerous greenhouse gases that affect public health. Transport's contribution to global warming is a commonly discussed global economic problem. The International Energy Agency (IEA) proposes a combination of both technological and behavioural measures: avoid, shift, improve and switch which will help to reduce carbon emission and improve the mobility in city.
Mobility is the degree of easiness for people and objects to pass about. Mobility needs to be understood in order to develop a reasonable plan for land use and transportation, and mobility initiatives need to be established which result in improving individual accessibility to opportunities. The data for indices of mobility and accessibility will be obtained through a combination of surveys, such as traffic volume surveys, speed and delay surveys, etc. Mobility can be understood by the Travel behavior indicators and transport infrastructure indicators.
1. Travel Behaviour Indicators
Access to different modes of transport, travel speed and time and distances people travel are considered indicators signaling that how moveable a person is. Moreover, they reveal the present travel behaviour of the residents. It further includes modal share, average travel time, average speed of vehicle on roads and average trip lengths. When presented together, travel time and distance offer a lot of information on transport network efficiency (longer travel time and congestion in low-speed signs, etc.). Trip length and time often reflect the average length of trips in a city and how much time is taken to complete it in various transport modes. Modal share indicates access to different modes and whether they are in favour of low carbon transport or not.
2. Transport Infrastructure Indicators
Indicators of transport infrastructure reflect transport supplies which indicate the quality and size of transport infrastructure. These also give an overview of the alternatives open to individuals to use their preference of mobility. The availability of connectivity also reflects the locational advantage / disadvantage for any mobility choice in the city and thus helps in the decision-making process on transport. Road density, junctions mean that higher road density increases the ease of travel, so that it can also lead to greater access to opportunities. This can also result in greater use of motorized transport models that are not included in the sustainable energy mobility strategy. Junction density indicates size of urban area. The higher the number of junctions, the smaller the urban block size, which encourages the use of non-motorized modes of transportation. Traffic volume survey is done to calculate PCU counts in a city. To assess the existing traffic and transportation situation it is important to conduct traffic volume survey. The Passenger Car Unit (PCU) as shown in Table-1.1 , values recommended by Indian Roads Congress (IRC) for urban roads are to be used in the analysis.
| Table-1.1 PCU standards | ||
| S. No. | Vehicle Type | Equivalency Factor |
| 1 | Car | 1 |
| 2 | Truck bus | 3 |
| 3 | Two-wheelers | 0.5 |
| 4 | Cycle-rickshaw | 1.5 |
| 5 | Animal-drawn vehicle | 4 |
| 6 | Hand-cart | 6 |
Source- IRC standards, 2001
PCU values are calculated by multiplying no. of vehicles by the standard equivalency factor. Then presentation of directional flow is done with help of bar diagrams. Directional flow is also studied if the road is two-way road.
Volume/Capacity ratio - Volume capacity ratio is a true indicator which tells about utilization rate of road. It is the ratio between the total traffic volumes in peak hours with the capacity of road as per standards. Standards for road capacity are given by Indian Road Congress as shown in Table- 1.2 .
| Table- 1.2 Highway capacity standards | ||||
| No. of traffic lanes and width | Traffic flow | Capacity in PCUs per hour for various traffic conditions | ||
| Roads with no frontage access, no standing vehicles, very little cross traffic | Roads with frontage access but no standing vehicles and high capacity intersections | Roads with free frontage access, parked vehicles and heavy cross traffic | ||
| 2-lane | One way | 2400 | 1500 | 1200 |
| (7-7.5m) | Two way | 1500 | 1200 | 750 |
| 3-lane | One way | 3600 | 2500 | 2000 |
| (10.5 m) | ||||
| 4- lane | One way | 4800 | 3000 | 2400 |
| (14m) | Two way | 4000 | 2500 | 2000 |
| 6- lane | One way* | 2600 | 2500 | 2200 |
| (21 m) | Two way | 6000 | 4200 | 3600 |
Source-IRC standards, 2001
Junction Capacity : - Junction capacity is calculated by multiplying the sum of all carriageway widths (w) of the leading junctions with the standard value (k), for three-way or four-way junction. Kadayali,L.R ., (2013) ,has given the following formula,
Junction capacity = kw,
Here, k=70 PCU for 3-way junction
k=80 PCU for 4-way junction
After finding the standard capacity of junction, Junction capacity is calculated which should be equal to 1. If it is more than 1, then it is critical junction which is facing problem of congestion. Junction capacity is calculated by dividing observed PCU on junction divided by standard PCUs of that junction.
Junction capacity = (Observed PCU) / (Standard PCU)
Degree of Congestion: The degree of congestion is the relative volume of the design speed on the road to the observed speed on that road. The degree of congestion is formulated as follows:
Dc = Sd-So
Sd
Dc – Degree of congestion
Sd = Design speed
So = Observed speed
Congestion Index: Congestion index examines the combined effect of traffic volume, road width and the observed speed. Congestion index is defined as follows:
C.I. = (Dc x V)
(Nc x Lane Capacity)
C.I. – Congestion Index
Dc – Degree of congestion
V – Peak lane volume of stretch
Nc – No. of Lanes
NMT facilities include pedestrian facilities and bicycle facilities. Pedestrian facilities enable individuals to make the option of walking as a mode of transportation to access resources. It is important to provide walkways which are broader than 2 m after being deducted for space lost due to intrusion. Appropriate treatment of intersections is also important to encourage pedestrian movement. Similarly, cycling facilities enable individuals to exercise the option of using bicycles as a mode of transportation for accessing opportunities. Some roads are needed to have separated cycling lanes and junctions to give priority to moving bicycles. Sufficient arrangements for bicycle parking also encourage bicycle use. City transport and intermediate public transport show that the people have greater access to public transport services.
Transportation safety is one of the most important urban transport issues. It includes that how many people feel safe to walk and use bicycle on the roads. It includes indicates that how safe an individual feel while using and accessing the transport facilities. It also include that how safe people feel especially women and children while using footpaths that whether footpaths and roads are lighted or not.
Environment considerations are important dimensions to be studied in detail. The first phase in calculating the environmental indicators – CO2 emissions and primary air contaminants – is quantifying energy use from transport. Data on the vehicle population and the average distance traveled by each type of vehicle that then be used to measure the total kilometers of the vehicle. Using data of total vehicle kilometers traveled (VKT), type of fuel, average fuel economy of each category of vehicle, and energy usage can be measured. (Refer Table-1.3 )
| Table-1.3 CO 2 Emission Coefficients | |
| Fuel Type | Kg CO2/ liter of fuel |
| Petrol | 2.3 |
| Diesel | 2.71 |
| CNG | 1.69 |
| LPG | 2.91 |
Source- IPCC, 2006
CO2 emissions can be calculated from the total fuel consumption based on the CO2 content of fuels. If available, local emission factors should be used. National emission factors (refer Table-1.4 ) are published by The Automotive Research Association of India. The air quality is a significant human health predictor. Transportation is a significant contributing cause of urban air pollution. The long-term valuation of ambient air quality data is helpful for, i) understanding prevailing trends and, therefore, prioritizing policies such as emission norms, policies on public transport, etc., and ii) understanding the effectiveness of policies. Air pollutant emissions from transport can be calculated by multiplying the VKTs with emission coefficients for different vehicles.
| Table-1.4 Emission Factors of Different Air Pollutants | |||||
| Emission Factors | Fuel type | CO (g/km) | HC(g/km) | NOx(g/km) | PM(g/km) |
| 2W | Petrol | 3.37 | 2.05 | 0.03 | 0.049 |
| 3W | Diesel | 9.16 | 0.63 | 0.93 | 0.78 |
| CNG | 1 | 0.26 | 0.5 | 0.015 | |
| Petrol | 3.01 | 0.51 | 0.75 | 0.49 | |
| Car | Petrol | 3.01 | 0.19 | 0.12 | 0.006 |
| Diesel | 0.06 | 0.08 | 0.28 | 0.015 | |
| LPG | 0 | 0 | 0 | 0 | |
| CNG | 0.6 | 0.36 | 0.01 | 0.002 | |
| Bus | Diesel | 2.56 | 0.51 | 0.32 | 0.22 |
Source-The Automotive Research Association of India (ARAI)
According to the report Monitoring GHGs Emissions of Transport Activities in Chinese Cities , “Volume capacity ratio and degree of congestion has direct impact on the carbon emissions. As the V/C ratio and degree of congestion increase, the flow of vehicles on the road also increase” as shown in table-1.5 .
| Table-1.5 Impact of LOS on Emissions | ||
| LOS impact on Emissions | Condition | Increase in Emissions |
| A | Free flow | - |
| B | Reasonably free flow | - |
| C | Reaching Unstable Flow | 5 to 10 % |
| D | Unstable Flow | 10 to 15 % |
| E | Forced Flow | 15 to 20% |
Source- Monitoring GHGs Emissions of Transport Activities in Chinese Cities HBEFA China, INFRAS 2014
It shows that when level of service reach C, that is reaching unstable flow conditions, then there is 5 to 10% increase in the emissions. Similarly, when it reaches D and E, there is upto 10 to 15% for D and 15 to 20% for E type, which is, forced flow conditions of vehicles on the road.
The wider strategy for sustainable urban transport aligns with low-carbon policies by building near to public transport nodes; encouraging walking, cycling and public transit as replacements to private cars; and regulating urban vehicle use. Some of the solutions which help in promoting low carbon mobility at city level are discussed as follows.
1 Comprehensive Pedestrian Network
Walking is not only a non-motorized mode of public travel, but it also releases zero carbon emissions. This does not cause a danger to the community. This is the most effective choice for short-distance travel in urban centers. It is necessary to connect the walking network with other operation nodes such as schools, universities, business centers, etc. and mass transit sites.. This helps to lower car reliance by building a robust network of pedestrians throughout the development area.
2 Comprehensive Cycling Network
Biking is indeed true option for low-carbon urban mobility; it is also vital to any new urban mobility network. From the viewpoint of a planner, biking trips are spatially efficient, demand low investment and give mobility beyond environmental impacts of noise, traffic, congestion or accidents. Public Bike Sharing System :- As per the Public Bike Sharing Guidance Document by Ministry of Urban Development , “Public Bicycle Sharing (PBS) is a high quality bicycle based public transport system in which bicycles, stored in a closely spaced network of stations, are made available for short-term shared use. Bicycle sharing programs involve installing multiple bicycle stations at several different key locations. A user checks-out the bicycle from one location, rides to his or her destination, and drops off the bicycle to another location”
3 Efficient and Low-carbon Public Transport System
Public transport is a reliable mode of transportation because it is capable of handling a large passenger traffic at once and providing a wide range of locations. According to Public Transport: Lessons to Be Learnt from Curitiba and Bogota Report , “40% of the population uses public transport as the commuting mode while in Hong Kong, more than 90% of the population depend upon public transport. This shows that public transport can be the preferred choice if the system works efficiently.” An effective transportation system will help to reduce the percentage of frequent commuters from using their own cars to mass transit by 10 to 40 percent, and it will help to reduce the emissions of each passenger per capita.
According to a source quoted from the Green Vehicle company , “electricity is approximately 80% cleaner than gas engine. Besides using electricity as an alternative, another way to achieve clean engine motor vehicles is via biofuel or biodiesel. These sources emit less CO2 compared to conventional petroleum and diesel fuels. Clean fuel on-road public transport modes can significantly reduce CO2 emission for each kilometer travelled.”
4 Low Carbon Private Transport
A traditional car is one of the top contributors to CO2 emissions. According to Chester, M. et al., (2010) , “the average conventional vehicle emits 6000 to 9000 kg of CO2 which leads to global warming potential. One of the effective ways to reduce CO2 emission from the conventional vehicle is to switch to a lower carbon type of vehicle, for instance, a hybrid vehicle. The combination allows the electric motor and batteries to operate the combustion engine more efficiently, thus cutting down on fuel use. As a result, this type of vehicle will produce less combustion, thus significantly reducing the CO2 emission. However, there are several barriers to using this type of vehicle such as the expensive battery technology, limited driving range and the need for a dense network of charging facilities throughout the city.”
5 Vehicle Speed Management
The average speed of automobiles varies in various situations according to road types. Speed limit helps reduce pollution. Of example, CO2 emissions can be minimized to a lower level in highly populated city areas, with a reasonable speed restriction. Many techniques may be used to implement efficient speed control and also to limit the amount of CO2 produced in the environment, which includes speed limits and technology methods. This is to make sure people are obeying the speed limits and the rules. That will also improve the road safety quality. Effective speed limit control thus helps to minimize fuel consumption, resulting in a decline in CO2 emissions to the environment.
6 Traffic Congestion and Traffic Flow Management
Traffic jams is a increasing global problem. Overcrowding exists due to increased vehicle ownership, easy access to a wide variety of community events, as well as lack of and challenging walking or cycling routes. People tend to use cars for getting only a short distance to their destination. Constructing more highways is therefore no longer a solution to these problems and can no longer be enforced because it adds to the growing number of cars thus releasing more CO2 into the atmosphere at the same time. According to Texas Transportation Institute; TTI's-Urban Mobility Report , “Stockholm, for example, managed to cut traffic gridlock by 20%, reduce emissions by 12% and increase public transport use dramatically through the Smart Traffic System. This shows that with appropriate traffic flow management, traffic congestion can be prevented and the amount of CO2 generated into the atmosphere will be lessened.”
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