In the United States, transportation represents a large part of the urban energy balance and plays a key role in economic activities. As a sector, transportation makes up 20 percent of global energy use and 50 percent of oil consumption. Urban transportation, which accounts for 40 percent of global energy expenditure on transportation, makes up 8 percent of the world’s total energy consumption. It’s also one of the largest contributors to pollution and CO2 emissions.
The International Energy Agency (IEA) has stated that, despite the better gas mileage of the growing percentage of hybrid and electric cars, the projected doubling in size of the global Light Duty Vehicle (LDV) fleet by 2050 will cause these energy consumption numbers to continue to grow. As such, solutions that leverage non-motorized transport (NMT) should be developed on top of the general advancement in automobile efficiency to decrease the reliance on LDVs. To solve these problems and create more efficient modes of transportation, the IEA has developed a three-part framework – Avoid, Shift, Improve.
“Avoid” relies on slowing rail growth through smart planning and the development of new pedestrian pathways that make NMT more attractive for urbanites. Solely implementing avoid techniques could reduce a total $30 trillion in vehicle, fuel and infrastructure expenditures by 2050. “Shift” depends on a move from private motorized vehicles to public motorized (and in some cases, non-motorized) vehicles. “Improve” pushes the auto industry to make small improvements to gas-mileage and develop alternative fuel sources for transportation. A combination of all three solution systems is expected to reduce energy expenditure by $70 trillion by the year 2050 (Ming Yang and Xin Yu, “Energy-Efficient Urban Transport).
Avoidance methods are used to decrease the need for transportation within urban areas by leveraging passive solutions that place people near where they need to be. Since energy consumption per capita decreases as density goes up, zoning for dense urban areas with mixed-use programs results in minimizing the amount of transportation needed to get to work, allowing urban dwellers to rely on walking or cycling.
Freight also benefits from the existence of megacities since goods can reach a larger number of consumers by traveling shorter distances. The introduction of centralized distribution warehouses near urban centers leads to a dramatic avoidance of last-mile transport – something that Amazon has begun doing in major cities across the United States. The key performance indicators for avoidance tactics include annual passenger miles, urban density and passenger transport energy use. Avoidance methods also include the development of teleconferencing techniques that allow for information and economic activity to travel without physical bodies doing so. As remote work becomes more widely accepted by large corporations, reliance on energy-guzzling modes of transport is expected to dramatically decrease.
By shifting the reliance on private modes of transportation and investing heavily in public modes of transportation within the urban core, cities can improve efficiency and increase the number of people moved per energy unit. Buses are a particularly good example of this, since they rely on the same infrastructure as privately owned vehicles and road incentives can be aligned to increase the use of public modes at a cost or tax to private modes.
One successful example of this is the TransMilenio project in Bogota, a system of buses that run on their own exclusive street lanes. This system accounts for 1.4M daily trips and saves travelers an average of 223 hours per year in traffic. It minimizes the number of vehicles on the road and increases the efficiency of each trip. Since it relies on shifting rights to pre-existing infrastructure and enacting a time tax on personal transportation by decreasing road space, the project only cost $5M/km which is significantly more affordable than the average $150M/km construction cost for metro systems. Other solutions, such as limiting parking to discourage driving to the central business district or congestion pricing, also serve to incentivize a shift to public transportation. Key performance indicators for this shit are analyses of modal shares of transportation, vehicle occupancy rates and energy use per passenger per mile.
Improvement methods mostly rely on vehicle-level fuel efficiency and are taken care of by automobile companies that are trying to differentiate themselves by new fuel sources, development of electric vehicles and improved gas mileage. This system can be measured by tracking the average gas mileage of the entire LDV fleet as well as the replacement rate of existing, non-efficient cars with hybrid or electric vehicles.
While the avoid-shift-improve methodology is a great framework for thinking about energy efficiency in transport, there are two larger shifts in the transportation industry that’ll play larger roles in decreasing fuel use and emissions: the rise of shared autonomous vehicles and the electrification of all modes of transportation. At any given time only about 10 percent of America’s car fleet is on the road – we simply own more cars than we need. Studies have also shown that ridesharing reduces driving distances by 27 percent and that per mile costs can be reduced by up to $0.34 when using ride-sharing services. Computational simulations for shared autonomous vehicles (SAV) have shown that each SAV could replace up to 12 regular cars on average. Additionally, energy use in SAVs is projected to go down by 12 percent as the inefficiencies of human driving are reduced. On an environmental level, pollutants would also dramatically reduce (GHG by 5.6 percent, SO2 by 19 percent, CO by 34 percent, NOx by 18 percent, volatile organic compounds by 49 percent and PM10 by 6.5 percent). Such numbers come from models that assume that the entire vehicle fleet is replaced by SAV, but that the current fuel mix remains the same. They also don’t take into account that car sizes could be smaller and more energy-efficient, nor that 30 percent of traffic in the central business district is cars looking for parking, a factor that would be virtually non-existent with shared ownership. Real world increases in energy efficiency would, therefore, be much larger than 12 percent.
The electrification of cars is also an important factor to consider in the development of energy-efficient transportation. By moving to electric, cars can run on renewable resources attached to microgrids, drastically decreasing emissions. A 100 percent renewable energy electric transport system would correspond to an energy demand decrease of around 18 percent, mainly because of a 69 percent reduction in the global demand for petroleum, which currently accounts for 94 percent of the total energy demand in transportation. While other green energy systems exist for urban transportation, they tend to be less efficient than pure electrification.
For example, fuel cell vehicles require 3.6 times more electricity consumption to generate hydrogen. Although electric vehicles are a great solution, the number of vehicles producible would only be able to match the current number of vehicles in the global fleet since any larger number would not be serviceable by the known supplies of Lithium and Nickel for battery systems.
Figure 4: Estimated energy used for present and future transport, by sector.
While personal vehicles are an important piece of the development of energy-efficient transportation, they’re just one piece of the transportation chain and aren’t as effective without shared ownership. Cities should invest in metropolitan and regional electric transport such as train systems which can carry 8 times more people per MW of capacity than a car. Additionally, last-mile transportation should rely heavily on bikes and walking in order to minimize electricity use for individual movement. Smaller electric scooters, such as the ones introduced by startups Bird and Lime are also good options since they don’t take up as much street area and are both cheap and easily accessible for short distances.
It would take $36 trillion dollars to fully electrify the global vehicle fleet, a transition cost equivalent to 33 percent of the gross world product (2016). While it’s infeasible for this transition to occur over the course of a single year, by slowly beginning to shift incentives away from non-electric modes of transportation, and making sure such energy comes from renewable, non-polluting sources, we can begin tackling the 25 percent of global greenhouse gas emissions that’s attributed to urban transportation and making our cities cleaner and more efficient places to live.