The development of urban road transport in the 20^th century (hereinafter referred to as urban transportation) is closely related to the national economic growth level (including growth rate and quality). For more than half a century from the World War II to the first ten years of the 21^st century, the highlights of world economic growth appeared in North America, Europe and East Asia. The developments of urban transportation in these regions are to seek a balance between building more roads for more private vehicles and increasing public transportation investments, supplies as well as improving services. As the increasing contribution of transportation to urban air pollution and the global efforts to deal with climate change, the traditional urban transportation decisions aiming at promoting GDP growth, improving population mobility, controlling transport congestion and providing cost-effective and safe public transport services, are facing challenges, which include social and environmental justice, inclusiveness of economic development, climate change and its impacts, public health and other factors resulted from the transportation decision process and activities, and a low-emission (including conventional pollutants and carbon dioxide emissions) transport system for the future. This paper discusses the policy framework of urban sustainable transport in the 21st century by combining the model of transport decision in the United States and the case of low-emission development of urban transportation in the city of Los Angeles.

The comprehensive decision for urban transportation

The transport system includes three interrelated fields: transportation policy and planning, design and construction of transport system, and operation, maintenance and disposal of transport systems after its service life expires. Although this paper mainly discusses the first aspect, consideration of the last two aspects will also affect planning and policies. In planning and policy decision-making, it should consider how to effectively cope with the waste from the end use stage of transport systems in the application of Life Cycle Assessment and how to implement a comprehensive transportation planning and policy decision making after taking into account the factors of investment and economic feasibility, as well as the design and construction of transport system, environment and user friendliness.

The complexity of urban transportation planning and policy decision-making is reflected in that it not only involves social issues (transport convenience, safety and distribution of transport resources), economic issues (affordability of travel time and financial costs, social and economic costs of congestion) and other issues, but also has a direct impact on urban environment (air pollution, water pollution, impact on natural ecosystem/biodiversity-habitat destruction-segmentation, noise, etc.), public health and global climate change. The policy decision-making framework for sustainable urban transportation in the 21^st century needs to break through the limitation of the urban areas and interests tangling, examine the problems and solutions from a long-term time dimension (e.g. more than 50 years) and a global perspective, break away from the previous traditional decision-making model, and establish a decision-making framework including new evaluation indicators:

• Whether to undertake the global responsibility to deal with climate change and promote the development of net zero emission in the transport sector as the goal;

• Whether to aim to improve the quality of urban environment, and continuously reduce the emission of pollutants harmful to public health;

• Whether to control the supply and demand balance of urban transportation resources, an important public good, to limit the growth of private cars and increase the capacity and level of various public transportation services;

• Whether to consider the inclusive nature of economic development to provide affordable, safe and reliable public transportation for the low-income urban population;

• Whether to integrate urban design and planning to provide support and solutions for the future low carbon development of urban areas.

Next, let's look at what American organizations, including government agencies, have done in enhancing the decision-making process in order to promote sustainable transportation development.

Low-emission transportation decision models

Each city has its own characteristics of the current transportation systems, and the basis and ability to achieve sustainable transportation with low emissions are also different. However, the abovementioned indicators are largely universal for sustainable low-emission transportation decision making in cities. The following decision-making models being used in the United States are worthy of noticing as they try to address the sustainability issues in the transportation policy making process. Here is a brief review.

GREET (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation) is an assessment model for greenhouse gases, pollutant emissions and energy use in transportation systems. It was developed and continuously updated by the Argonne National Laboratory of the U.S. Department of Energy. This model aims at how changes in energy and transportation policies lead to changes in output throughout the life cycle of energy use. For example, if in the next five years, 30%-50% of the passenger car is driven by charging electric or hybrid power, how much carbon will be reduced for the full life cycle of the U.S road transportation and the how much cost it will take.

Traffic decisions cannot be made without urban planning and community design. The namesake decision model developed by EcoDistricts, a non-profit organization, focuses on decision-making at the community level and helps integrate infrastructure, construction and transportation decisions into community actions. This model is currently developing four decision-making frameworks, covering institutional organization, performance and evaluation, financing and policy support. This decision-making framework involves many new concepts and technologies, including bicycle lanes, green streets, community energy and water resources management, public art and smart grid.

UrbanSim/UrbanFootprint is an interesting model for how to consider sustainable transportation in urban planning decisions. This model supports the planning and analysis of urban development and integrates land use, transportation, economy and environment into the decision-making process, which helps to discover the impacts of policy changes and infrastructure on communities, such as the convenience of transportation, housing affordability and corresponding carbon emissions. With the aid of the model, scenario analysis can be done, for example, how to take economic, environmental and public health factors into consideration, so as to make analysis of future transportation development under different scenarios.

Local governments in the United States, including states and cities, also use modelling methods in decision-making. For example, New York State Department of Transportation has developed the GreenLITES Model for sustainable development of transportation and environment, in order to recognize and promote the integration of sustainable development methods into planning, project design and evaluation related to regional transportation development by state decision makers, thus to improve the sustainability of transportation systems.

Similarly, the Illinois State Department of Transportation has also developed a tool: Illinois-Livable and Sustainable Transportation Policy Tool (I-LAST), which provides a detailed list of sustainable practices and a brief method for evaluating whether a project is sustainable. This tool aims to minimize the impact on the environment, reduce resource consumption and energy consumption. The tool is highly practicable because it provides a set of lists of potential sustainable practices that can be referenced and includes a corresponding list of raw materials for each practical operation, which greatly helps decision makers to put concepts and methods into practical operations.

These models suggest that policy makers urgently need a decision-making framework or model that can comprehensively examine and consider sustainability from the life cycle of the transportation system. As model developers are often among the stakeholders of policy decision-making, from the perspectives of organizational structure, experience, habits and specialty, the models are usually focused on one specific aspect, and lack a macro and long-term strategic perspectives to think about what kind of the decision-making framework for future sustainable low-emission transportation should look like. Such challenges have been fully recognized by the researchers in this field. The Transportation Research Board (TRB)² of the United States published a series of "Strategic Issues of Transport" reports in 2015. One of the reports, entitled "Sustainability as an Organizing Principle for Transportation Agencies", analyzes how transportation agencies manage and organize to support a more sustainable society. The model explains in detail how to focus on long-term and systematic methods to provide public services from immediate and short-term interests. One concept put forward in the report is "Triple-Bottom Line (TBL), that is, economic, environmental and social factors should be measured and calculated as the bottom line in decision-making. "The TBL is a comprehensive concept that does not exclude any policy areas and systems. It is difficult to isolate the transportation system because transportation has the fundamental attribute of integration with other human activities. Sustainable transportation requires considering a broad definition of sustainability. Under such requirements, it is necessary to consider how transportation affects the sustainability of the whole society and how policies other than transportation coordinate and cooperate with each other to achieve sustainability.”³

TRB’s latest report Critical Issues in Transportation 2019 points out 12 critical issues,⁴involving transportation system governance (decision-making and institutional arrangements, system performance and asset management, investment and financing, and cultivation of more efficient and diversified transportation human resources); how to develop a low carbon transportation system; fairness, safety and health of transportation services and resilience to population changes and frequent disasters; research and technological innovation in the management of transportation, as well as the discussion by a special department on protecting the ecological environment and achieving sustainable development. In fact, these 12 critical issues are all related to the sustainable development of the transportation system, in which the transport sector governance, technological innovation and energy transformation are the top priorities. Many local governments have already made efforts to take immediate actions to seize the short time window to deal with climate change and introduce the transportation system into the track of sustainable development. Next, we will briefly observe a case. This city was a global model of urban development in the 1960s and 1970s, encouraging private car ownership, and building ever expanding highway network. However, it is currently making a fresh start to create a low carbon urban development model that responds to climate change, local air pollution and green economic growth with sustainable transportation as one of the cores of policy initiatives and development model innovations.

Los Angeles: Rebuilding a global model?

Los Angeles County (Greater Los Angeles area with the city of Los Angeles as its core and more than 80 cities included) covers an area of more than 10,000 square kilometers, has a population of more than 10 million (4 million people in the city of Los Angeles), and its total economic output (GDP) exceeded 1 trillion U.S. dollars in 2017, ranking the 16^th position in the world’s GDP in the same year.⁵

On average the residents in Los Angeles County lost 61 hours per year due to congestion. Los Angeles has been ranked as the most congested area in the United States for more than a decade.⁶ Facing the worst situation, Los Angeles has been making changes in the past ten years. In Regional Transportation Planning 2012-2035, Los Angeles County Metropolitan Transportation Authority plans to invest 525 billion US dollars to develop sustainable transportation by 2035.⁷ By 2012, Los Angeles’s public transportation networks such as subways, light rails, liquefied natural gas (LNG) bus lines, bicycle lanes, and so on. have increased significantly.

Los Angeles’s transportation and construction sectors account for three quarters of all carbon emissions.⁸ Moreover, Los Angeles has undoubtedly placed transportation emission reduction in a key position in its action to mitigate climate change. Los Angeles has already put forward a more active target of reducing emissions in 2015. Under the leadership of Mayor Eric Garcetti, who regards tackling climate change as the most important task in his administration, Los Angeles further launches a “Green New Deal”⁹ in 2019 and sets more ambitious targets for mitigating climate change. Here are only the contents related to transportation and urban planning:

• By 2045, the power system will achieve 100% renewable energy supply;

• By 2035, 80% of passenger cars are powered by electricity or zero-emission fuels, while 80% of the electricity supply comes from renewable energy;

• By 2050, 100% of vehicles will be electric vehicles or zero-emission vehicles, and by 2030, public transportation including rails and buses will be 100% electrified;

• Port-related carbon emissions will be reduced by 80% against the level of 1990 by 2050;

• The number of public charging stations for electric vehicles will reach 28,000 by 2028;

• Vigorously developing public transport (by 2035, 50% of the trips will be made up of low carbon modes such as walking and cycling);

• Implementing public transport-oriented urban design and planning (by 2035, 75% of new residential buildings will be located within 1,500 feet of public transport stations);

• Using reverse incentives (charging higher road tolls in heavily congested areas), Los Angeles plans to reduce the average daily driving distance of residents from 15 miles around 2017 to 13 miles in 2025 and 9 miles in 2035.

Los Angeles has set an action targets full of opportunities and aspirations. Maybe by 2030, we can judge whether Los Angeles has realized its objectives and recreated a model of world-class city’s low carbon development based on the facts and experiences.

Conclusion: What kind of cities do you want to live in?

From the macro point of view, sustainable transportation development requires us to rebuild the social development model and policy decision-making framework, and we need to balance thinking and making decisions about our future from the “Triple Bottom Line” of society, environment and economy; from a micro point of view, the realization of sustainable transportation depends on every citizen’s action to answer the question: What kind of urban environment do you want to live in in the future? Responding to climate change is the most urgent and important issue in the field of sustainable development, as well as in the field of transportation. Under the Paris Agreement, most governments have been taking various actions to reduce greenhouse gas emissions under the constraints of their own capabilities and resources. However, the current trajectory of global mitigation efforts cannot achieve the goal, to keep the global average temperature rise no more than 2 ℃. Therefore, more and more non-state (government) actors, from commercial enterprises, to community organizations, environmental groups and individual citizens, are taking part in the initiative to make changes from the bottom up. In the next ten years, these two currents, both top down and bottom up approaches will work together to bring sustainable development and low carbon development to the core of all parts of human activities, including the transport sector. The cities, where vast majority of population across the globe will live and work in the future, will become more socially inclusive, economically dynamic, technologically creative, environmentally healthy, and naturally sustainable for their citizens. This might be the ideal future city each of us would like to live in.

References

1. The so-called sustainability should involve environmental, economic and social sustainability. Specifically, it should refer to environmental sustainability (climate change), vitality of economic development and sharing of growth/values, social inclusion, multiple integration and mutual respect (avoiding the disparity between the rich and the poor and ethnic confrontation based on beliefs and values).

2. TRB is one of the six main branches of the National Research Council of the United States. It is managed by the United States National Academy of Sciences, the National Academy of Engineering and the National Academy of Medicine and has a history of nearly 100 years. This interdisciplinary and cross-disciplinary research institution is leading the way in promoting innovation and progress in the transportation field in the United States through research and information exchange.

3. NCHRP Report 750 Volume 4: Sustainability as an Organizing Principle for Transportation Agencies

4.“Critical Issues in Transportation 2019: Policy Snapshot” Link：http://onlinepubs.trb.org/onlinepubs/policystudies/criticalissuesbrochure.pdf

5. According to Stastata.com’s data on GDP comparison.

6.Achieving a Lower Carbon and More Sustainable Transportation System, Pam O’Connor. Link：https://sustainabledevelopment.un.org/content/documents/3724oconnor.pdf

7. Same as footnote 6.

8. The data quoted in this paragraph is from an interview with the Mayor of Los Angeles in Los Angeles Times, published on April 29, 2019, entitled Los Angeles Mayor Proposes Ambitious Sustainability Plan. Linkage: https://www.govtech.com/fs/transportation/Los-Angeles-Mayor-Proposes-Ambitious-Sustainability-Plan.html

9. Links to “Green New Deal Plan”: https://plan.lamayor.org/targets