I referenced a study of a Life Cycle Assessment of Infrastructure in one of my previous posts. Now that I have reviewed some of the data and results, I wanted to address how this study can help our public policy planning. In my opinion, the most valuable information of this study can be found in the section on “sensitivity to passenger occupancy”. Shown graphically in Figure 3, the ranges of energy input and pollution per Passenger Kilometers Traveled (PKT) are associated with ranges rather than a single number.
What this shows is that certain vehicles are more sensitive to occupancy than others. Sensitivity in order as follows:
- On-road vehicles
- Rail Systems
The on-road vehicles are quite variable, whereas the airplanes and rail systems vary only a small amount. This is because the tailpipe emissions of airplanes and rail systems only account for a small amount of overall emissions (infrastucture and fuel source play a large role).
One bright spot for bus enthusiasts is that a fully occupied rail system is about as efficient per passenger as a fully occupied bus. SUV vehicles are rarely efficient, even when fully occupied.
The Greenhouse Gas (GHG) issue is also important, especially since GHG emissions must be cut and reduced within the next few years. This study shows that a rail transit system is the best option to reduce GHG emissions. It also shows us that a coal powered transit system (e.g. Boston Green Line) is not effective at reducing emissions.
Probably the most important issue, and one this study cannot address directly, is the overall energy inputs and GHG emissions for each transportation mode. While this study offers great data on PKT rates, the other side of the equation is actual distance travelled by each passenger. Urban sprawl generates a system whereby people must travel long distances using the most inefficient form of transit available. We are building potential high costs (energy and GHG) into our transit systems. This can be just as serious an issue as the mortgage crisis which crippled the US economy.
With public transit, people travel smaller distances and do so on more efficient systems. Transit-oriented development (TOD) offers an opportunity to connect neighborhoods to the urban core without relying on automobiles. People travel shorter distances and use the most efficient form of transit available today.
Air travel for long-haul flights can still play an important part of the US system, but the airports should be served by public transit systems and not just rental car facilities. Connectivity is a very important feature, and removing automobiles from transit systems requires intermodal options at every point.