I do not remember how or when I came across this specific article- “Environmental assessment of passenger transportation should include infrastructure and supply chains”- but I was initially captivated by the way its authors, Mikhail Chester and Arpad Horvath, analyze ways of more accurately accounting for environmental impacts of transportation, providing a more holistic approach to comparing different transportation modes (Figure 1)1. They specifically account for infrastructure, fuel production, and supply chains.
Figure 1. Energy consumption and GHG emissions per passenger-kilometer traveled (PKT) (The vehicle operation components are shown with gray patterns. Other vehicle components are shown in shades of blue. Infrastructure components are shown in shades of red and orange. The fuel production component is shown in green. All components appear in the order they are shown in the legend.)1.
Personally, one of the most interesting results of their analysis is the stark difference in energy consumption (~350 MJ/PKT) and emissions (~350 g CO2e/PKT) between off-peak and peak hours within public transportation, i.e. urban diesel buses. I would assume that the significant differential relationship would still hold true using other fuels such as gasoline and natural gas, since the values are normalized per passenger-kilometer traveled. It is also counterintuitive to see that peak-hour urban buses are a significantly better alternative to light rail when fuel production and infrastructure construction and operation are taken into account.
Over the years, Chester and Horvath’s article has made think about how to reduce the energy consumption and emissions of off-peak periods so that it looks more like peak-hour periods (waste reduction). Two possible starting points are technological innovation or increasing ridership. Actually solving this conundrum could make busses a more attractive alternative to building new rail for cities that do not have a rail system already, since rail requires high upfront investment and long-term implementation due to infrastructure development. I was “stuck” for a while with no answers, until I came across the first bus rapid transit (BRT) system in Curitiba, Brazil, built in 1974, where it was estimated that a new subway system would cost over $90 million per kilometer, compared $200,000 per kilometer of new BRT construction2.
There is no universal definition of a BRT system, but the best ones are characterized by efficient ways to provide convenience and comfort to passengers while improving system performance, in essence providing the speed and reliability of light rail, but on wheels. The benefits behind implementing a successful BRT system is not only a cost-effective alternative to light rail, a mechanism to increase ridership due to convenience and reliability, but also a flexible system that is able to expand and/or readjust routes based on future demographic and land-use changes (something more difficult to deal with when a fixed light rail system is in place).
Similar to LEED buildings, the BRT Standard has recently (piloted in 2012) provided a scoring system that results in Gold, Silver and Bronze certifications based on the criteria described in Figure 2 and Figure 3.
Figure 2. BRT Standard Scorecard consists of five sections: service planning, station design and interface, quality of service and passenger information systems, and integration and access3.
Figure 3. Duke’s Center on Globalization, Governance, and Competitiveness at the Social Science Research Institute’s representation of different BRT components: 1) Station 2) Branding 3) Passenger communication 4) Vehicle 5) Information technology 6) Integration and access to other transportation modes 7) Fare collection 8) Infrastructure and restricted lanes 9) Frequency and convenient operational services 10) innovative finance mechanisms4.
Curitiba’s permanent success, where 75% of total travelers use BRT and 28% of its 1.3 million riders switched from personal vehicle to using the BRT system, is due to5:
- Frequency and Convenience. The arterial streets that are most used by passengers provide express busses that may come as often as every 90 seconds. Buses are equipped with sensors to inform passengers of delays2. Passengers are also only required to pay a single fare with no additional fees to transfer between busses at terminals where different buses intersect.
- Bus Service Hierarchy. Buses are given protected and given the right of way, decreasing travel time (Figure 4). Additionally, Instead of using one size for all buses, Curitiba uses minibuses along residential neighborhoods that feed into the arterial routes serviced by medium-sized buses. It is only the major corridors that passengers are serviced by mega buses. Moreover, buses are color-coded based on ring-zones and route, a distinct part of the branding process2.
- Accessibility and Comfort. Bus stations are elevated and covered, providing comfort during inclement weather. The elevated stations provide a leveled platform that makes boarding the bus quicker and provides a good system for pre-boarding fare collection. A bus will on average spend 15 to 19 seconds at a stop with the exchange of passengers, increasing operational performance.
- Land-Use Policies. Curitiba intentionally favored zoning policies that promotes high-density development along the corridors served by BRT routes (land within two blocks). Furthermore, density decreases the farther away one is from the corridors. Also, there is very limited public parking in the downtown area, forcing employees to use the BRT.
- Financing. A new infrastructure was not built, but rather modifications and updates were progressively constructed over the past 30 years6. Unlike the US, the BRT system in Curitiba is serviced by ten private companies that are paid by distance traveled rather than passenger volume.
Figure 4: Possible configurations of bus-way alignment to reduce congestion and delays due to turning conflicts and obstructions4.
Returning to my initial question: how do we reduce the energy consumption and emissions of off-peak periods so that it looks more like peak-hour periods? It seems to me that while many rely on technological innovation (e.g. hybrid vehicles) as the solution, ignoring ridership decreases the potential reduction of energy consumption and defeats the purpose of providing public transportation. With respect to ridership, most of the people I know, including myself, sometimes (or many times) prefer a personal vehicle to public transportation due to a bus’s unreliability and inconvenience (lack of access to where we need to go in a timely manner). Curitiba has shown the world, specially the U.S., that public transportation can address these issues. Nevertheless, it seems to me that Curitiba was able to come up with revolutionary solutions due to new policies and reformation of existing policies that went beyond a narrowly defined transportation sector. If U.S. cities are interested in saving its public transit system, they will need to address its current zoning, funding, operational, and development policies through a multi-sector perspective.
 Chester, M. V., & Horvath, A. (2009). Environmental assessment of passenger transportation should include infrastructure and supply chains. Environmental Research Letters, 4(2), 024008.