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Future transportation projects and services may have far different impacts than is currently the case, and planners may be challenged both by estimating novel forms of impact and overcoming the prevailing perceptions amongst professionals, policy makers, and the public.
I've long been intrigued with varying levels of effort and accuracy in assessing the longer-range implications of transportation policy and investment decisions. It is common to assess impacts 25 or 30 years in the future. For capital intensive projects, this comparison point design year often occurs when the investment is perhaps 15 years old (as it takes 10- to 15-plus years to implement many long-range plan projects) and perhaps halfway through the life of the asset being studied. As we are now entering a time period with an even greater pace of change, it is becoming increasingly difficult to assess both the market acceptance of an investment as well as its performance and impacts.
The energy use and environmental impacts of transportation provide good examples of this dilemma. In the first session of every course I teach, we do round-robin introductions where students share their motivations for taking the course. When I teach a public transit course, it's not uncommon for a third or more of the students to express their motivation to address climate change and energy challenges by providing better public transportation. The implicit assumption is that public transportation is a more resource efficient means of moving people. That premise is indeed supported by historic and particularly international conditions, where public transportation has been able to deliver resource efficient mobility. However, the world has been changing, and evidence suggests the pace of change is quickening. Not only do we struggle to develop reasonable future year assumptions, but often planners don't even rely on the most current or contextually relevant data on modal efficiencies when evaluating design year conditions. So for fun, let's look at the energy use metrics for electric means of urban travel.
Energy efficiency and emissions are critical considerations for a significant share of the public, and they are also significantly influenced by technology. This example looks exclusively at electric vehicles, where power generation and transmission efficiency differences can be ignored and only point of consumption of energy use is compared (making a 10 percent adjustment for charging inefficiencies for battery powered personal vehicles). Imagine, for example, evaluating transportation investments for a 2040 design year, when one might reasonably expect a large share of the vehicle fleet, particularly for urban operations, to be electrically powered vehicles. The table below itemizes energy efficiencies per passenger mile for various technologies that exist today. Admittedly, these technologies are likely to evolve over time, and the composition of the vehicle fleet operating on a planned facility is likely to change over time. In addition, the energy ratings for personal vehicles may not match real-world deployment. The light rail vehicle numbers shown in the table represent agency reported actual energy consumption in real operating conditions for several newer light rail systems.
1. Energy use based on USEPA MPGe ratings debited 10 percent to account for charging efficiency, occupancy based on 2008 NHTS average of work occupancy and overall personal vehicle occupancy.
2. Tuber might be the car developed by the partnership between Toyota and Uber while Goof might be the code name for the Google and Ford partnership. Or perhaps a Google and Uber partnership will produce a Guber vehicle. Low occupancies may result from these automated vehicles shuttling empty between assignments.
3. Energy use based on the company website assumes no charging losses, average bus occupancy based on APTA Public Transportation Fact Book, 2015, Table 5 bus passenger miles, Table 6 bus vehicle miles.
4. Based on Federal Transit Administration 2014 test of BYD 40 foot electric bus.
5. Based on manufacturer's website data; debited 10 percent for charging losses.
6. Based on 2013 agency submittals to the National Transit Database, LRT electricity use, passenger miles of travel, and vehicle miles of travel.
The data in the table is likely to surprise individuals who have not closely followed changes in energy consumption and vehicle utilization. This table suggests two sets of observations:
Comparative energy efficiency:
Implications for planning:
This scenario only touches on the challenges of planning for future transportation needs. The prospects of business models that treat mobility as a service, emerging technologies and propulsion systems, and ultimately automated vehicles, coupled with economic and demographic changes, create an extraordinarily challenging planning environment. Various analysts have speculated on the changes in the demand for travel with highly variable scenarios each having credible back-stories (Ken Laberteaux, Suzanne Childress, Johanna Zmud, Zia Wadud). Planners will be left with the daunting task of identifying plans that accommodate uncertain mobility needs, evaluating those plans credibly and objectively, potentially challenging current perceptions, and communicating risk and uncertainty to the decision-makers. That should be enough to keep planners busy for a while.
The opinions are those of the author—or maybe not—but are intended to provoke reflection and do not reflect the policy positions of any associated entities or clients. [email protected]