Editor’s Note: The following was originally posted to the Oregon Transportation Reform Activists Network (OTRAN) email list (you can subscribe here).
In order to actually meet targets for reducing greenhouse gas emissions, Oregon must do the math to determine that proposed steps will be sufficient. I offer the “Basic Equation of Transportation Greenhouse Gas Emissions” as a tool for examining the interplay of the five major factors: overall reduction target, share attributable to the transportation sector, population growth, changes in technology, and changes in travel behavior. Under reasonable assumptions, I find that in order to meet the targets for reducing greenhouse gas emissions, statewide vehicle miles traveled (VMT) per person will need to be reduced 18% by the year 2020, 33% by the year 2035 and 62% by the year 2050. Note that the first two benchmarks are within the planning horizons of regional transportation plans (RTPs) for Oregon’s six metropolitan areas, none of which are planning for anywhere near these kinds of reductions. A future post will discuss what making such needed reductions in VMT would actually mean for Oregon’s transportation system.
Warning: Math at the sixth grade level ahead!
Dear OTRAN friends,
Last December in “Framework Part 1: The New Direction for Oregon” (12/5/07), I proposed:
The New Direction for Oregon: All proposed, laws, rules, plans, policies and other actions must be judged in terms of how effectively they keep Oregon on track reducing greenhouse gas emissions. Proposed efforts taking us in the wrong direction must be rejected. Efforts that don’t go far enough must be strengthened to keep us on track. Every year and at every level, Oregon must assess how well it is doing compared to the House Bill 3543 targets, and make adjustments as necessary.
More recently in “Gov. Kulongoski re transportation and climate change: Part 2—glass half empty or half full?” (4/17/08), I challenged Governor Kulongoski and other state leaders to “show us the numbers that explain in detail how Oregon can move from business-as-usual to where we need to go.”
But it is easy to challenge others, and even easier to set ambitious goals. Instead, we need to roll up our sleeves, take out our slide rules,1 and begin the critical work of re-engineering the Oregon’s future to meet Oregon’s ambitious, but essential, targets for reducing greenhouse gas emissions, in particular, from the transportation sector.2
Basic Equation of Transportation Greenhouse Gas Emissions
The starting point for re-engineering Oregon’s future is what I term the “Basic Equation of Transportation Greenhouse Gas Emissions”:
(Total Emissions) × (Transportation Sector) = (Population) × (Technology) × (Behavior)
Before I explain in detail each factor in this equation, which involves only simple multiplication, I’ll point out that there are many solutions to this equation—and even more non-solutions. This equation does not dictate a single future, but merely reflects the fact that numbers don’t lie. For example, we can’t propose taking baby steps to reduce greenhouse gas emissions and expect these will add up to meeting the ambitious House Bill 3543 (2007) reduction targets.
I’ll also note that the equation involves five factors, each measured relative to today’s values. The factors will assume different values at different points in time, for example, today, the year 2020, the year 2035 or the year 2050.
In particular, one trivial solution to the equation is where we are today with all the factors equal to 1:
1 × 1 = 1 × 1 × 1 (year 2008)
As we look to re-engineer the future, we can adjust each of these five factors—think of turning each of five knobs up or down—subject to the constraint that the equation remain true.
Let’s look at each factor in detail…
The Total Emissions factor in the Basic Equation represents the total annual emissions from all sectors relative to today’s emissions.
Today in 2008, Oregon’s total greenhouse gas emissions are roughly 70 million metric tons of carbon dioxide equivalent (MMTCO2E) per year. In 1990, the figure was 55.5 MMTCO2E per year.3
For purposes of illustration, I am going use the year 2035 as a medium-term point in the future, far enough away to begin seeing real changes but not so far away that there is too much uncertainty. In particular, the Metro Regional Transportation Plan (RTP) currently under development goes out to the year 2035.4 The RTPs for other metro areas will also need to plan out to roughly that year. Thus the year 2035 is within the timeframe of current transportation planning processes.
Oregon’s greenhouse gas reduction targets set in House Bill 3543 (2007) call for reducing emissions by the year 2020 to roughly 50 MMTCO2E per year (= 10% below the 1990 level) and by the year 2050 to roughly 13.9 MMTCO2E per year (= 75% below the 1990 level).5
As the year 2035 is halfway between 2020 and 2050, if we are to stay on target, Oregon’s total greenhouse gas emissions in 2035 should be halfway between the 2020 and 2050 targets, i.e., roughly 32 MMTCO2E per year.
Recalling that today’s emissions are roughly 70 MMTCO2E per year, the Total Emissions factor for the year 2035 is (rounded to two decimal places):
(Total Emissions) = (32 MMTCO2E) / (70 MMTCO2E) = 0.46 (year 2035)
In plain English, Oregon needs to cut total greenhouse gas emissions by the year 2035 to just 46% of today’s level in order to stay on track.
The Transportation Sector factor in the Basic Equation represents the fraction of the total annual emissions attributable to the transportation sector relative to the fraction today.
According to the Governor’s Climate Change Integration Group (CCIG), the transportation sector accounted for 36% of Oregon’s total greenhouse gas emissions in 1990 and 34% in 2004.6
In theory, one could imagine a future in which the transportation sector accounted for anywhere between 0% and 100% of total emissions.
In practice, as Oregon looks to meet its targets, there will be some political negotiation around how much each sector must do to reduce greenhouse gas emissions. If one sector does less, other sectors will have to do more.
A reasonable policy decision is to plan for each sector to continue to account for the same fraction of emissions as it does today, in particular, that the transportation sector continue to account for 34% of all emissions. Under this policy decision, the Transportation Sector factor for the year 2035 is:
(Transportation Sector) = (34%) / (34%) = 1.00 (year 2035)
But an argument can be made that other sectors, in particular, residential, commercial and industrial uses, should be required to reduce emissions relatively more than the transportation sector: It is more practical to have low- or zero-carbon sources of energy for uses at fixed locations connected by a network of electrical power lines than for millions of personal motor vehicles traveling all over the place. In this case, the Transportation Sector factor would actually be larger than 1, reflecting that the sector’s share of emissions is increasing. We will return to this policy option below.
The Population factor in the Basic Equation represents the population relative to today’s population.
At least for the purposes of this discussion, we don’t have much control over population and it is just a fact of life. Thus the Population factor for the year 2035 is (rounded to two decimal places):
(Population) = (5.15 million) / (3.75 million) = 1.37 (year 2035)
In plain English, by the year 2035 the population is projected to grow to 137% of its current level.
The Technology factor in the Basic Equation represents the effect of technological changes on greenhouse gas emissions relative to technology today.
This factor subsumes all factors affecting the greenhouse gas emissions per vehicle mile traveled: vehicle fuel efficiency, fuel cleanliness and/or carbon content, transportation system changes to increase the experienced fuel efficiency of travel, etc.
Indeed, this factor subsumes three of the four specific ideas Governor Kulongoski highlighted in his recent speech to the Oregon Environmental Council Forum for Business and the Environment:
* low carbon fuels;
* vehicle technology improvement, including the shift to plug-in and electric cars; and
* improving transportation system efficiency.
Now it is notoriously difficult to predict where technology will be, say, 25+ years in the future. One can optimistically assume that technology will save us, even if that technology isn’t widely available and affordable today. Or one can pessimistically assume that there will be no improvement in technology, at least until it is actually commonplace.
Today, the fleet average fuel efficiency for cars and light trucks sold in the United States is just 25 miles per gallon (mpg). The Bush administration recently proposed rules that would mandate this figure rise to 35 mpg by the year 2020, a 40% increase.9 (Of course, just because the federal government proposes something doesn’t necessarily make it so.)
In comparison, a Toyota Prius, the best-selling hybrid in America, gets an estimated 51 mpg, even in the city.10 But currently all hybrids make up only 2.2% of the U.S. auto market, barely a drop in the bucket.11 Even once improved technology is available, it can take years or even decades for it to be widely adopted.
In trying to gaze into and re-engineer the future, I suggest a middle approach. In particular, I suggest taking the proposed new federal fuel efficiency rules for 2020 at face value. But I also suggest that this 40% increase in fuel efficiency be assigned to the year 2035, as it does take years for people to replace older cars with new.
Now increasing fuel efficiency by 40% translates to reducing fuel consumption, hence emissions, all other factors being equal, by 29%.12
In addition, I generously suggest that all other technological improvements, including further improvements in fuel efficiencies beyond the proposed 2020 targets, the increased use of hybrids and fully electric vehicles, non-carbon fuels and cleaner carbon fuels, and transportation system changes that result in greater operational efficiencies, account for an additional 21% decrease in emissions.
In plain English, I suggest that as a result of all technological changes, vehicle emissions in 2035 can be cut to just half of what they are today, mile for mile:
(Technology) = 0.50 (year 2035)
Last but not least, the Behavior factor in the Basic Equation represents the effect of behavior changes on greenhouse gas emissions relative to behavior today.
The Behavior factor subsumes factors related to how much people choose travel, as measured in vehicle miles traveled (VMT) per person. Thus it incorporates the effects of trip lengths, frequency, carpooling, mode splits, and so on.
Indeed, this factor subsumes the fourth specific idea Governor Kulongoski highlighted in his recent speech to the Oregon Environmental Council Forum for Business and the Environment:
* reducing the vehicle miles traveled.
We could argue about what sorts of changes in behavior are likely or desirable. But the magic of numbers not lying, i.e., of the Basic Equation of Transportation Greenhouse Gas Emissions, is that any four factors determine the fifth.
In particular, given our settings for the other four factors, it is necessary that:
(Behavior) = 0.67 (year 2035)
If this is the case, then the Basic Equation holds true:
(0.46) × (1) = (1.37) × (0.5) × (0.67) (year 2035)
In plain English, by the year 2035 each person needs to travel, on average, just two-thirds as much as they do today.
Put another way, VMT per person needs to decrease on average by 33% by the year 2035.
I recall that years ago the Oregon Transportation Planning Rule called for metropolitan areas to reduce VMT per person by 5%, 10% or even 20% over a period of decades. But such targets were amended by the Land Conservation and Development Commission, under pressure from the metropolitan areas, to require only more achievable steps towards reducing VMT.13
For example, the recently adopted regional transportation plan (RTP) for the Eugene-Springfield-Coburg metropolitan area plans for a slight increase in VMT per person between now and the year 2031.14
Thus the idea of reducing VMT per person by 33% by the year 2035, given recent history, is farfetched to say the least.
But the numbers don’t lie and a 33% reduction by the year 2035 is exactly what will be required, assuming the other four factors are as specified.
As I noted above, the Basic Equation does not predict the future nor does it have a single solution. The Basic Equation is merely a useful tool for exploring different possible futures, for asking “what if?” questions.
If we continue to focus attention on the year 2035, and if we take the Total Emissions and Population factors as fixed, then we can adjust the Behavior factor if we also adjust the Transportation Sector and/or the Technology factor.
For example, if we allow the transportation sector to grow from 34% of all emissions today to, say, 50% by the year 2035, then this growth would allow us to keep VMT per person constant, and thereby to avoid having to make significant changes in behavior. But doing so would be at the expense of all other sectors, requiring them to reduce their emissions not to 46% of today’s level but even further to 35% of today’s level.15 It would have to be a policy decision, heavily affected by politics and what is technologically feasible, to impose less ambitious targets on the transportation sector while imposing more ambitious targets on other sectors.
Another possibility would be to rely more heavily on technology, planning for emissions mile for mile to be cut not merely in half but actually to one-third of today’s levels. For example, this could be accomplished by increasing average fuel efficiencies from 25 mpg today to 75 mpg in 2035, or by a combination of technological measures. But it would be foolhardy today to plan for technology to improve so dramatically and thus to forgo opportunities to change behavior, i.e., to reduce reliance on motor vehicles.
The Years 2020 and 2050
Rather than focusing on the year 2035, we can also look to the year 2020 or 2050.
As a shortcut, one can set the other four factors using reasonable values and then solve the Basic Equation for the needed Behavior factor:
(Behavior) = (Total Emissions) × (Transportation Sector) / (Population) / (Technology)
For the year 2020, we get:16
(Behavior) = (0.71) × (1) / (1.16) / (0.75) = 0.82 (year 2020)
In plain English, under reasonable assumptions, by the year 2020 we need to see people driving just 82% of what they do today, in other words a reduction of 18%.
For the year 2050, we get:17
(Behavior) = (0.2) × (1) / (1.6) / (0.33) = 0.38 (year 2050)
In plain English, under reasonable assumptions, by the year 2050 we need to see people driving just 38% of what they do today, in other words a reduction of 62%.
I don’t intend the discussion above as a prediction of the future nor as detailed policy recommendations.
Rather my main point is that numbers don’t lie and if Oregon is going to actually meet our targets for reducing greenhouse gas emissions, we need to think like engineers and determine how to make the numbers work out.
I’ll also note that the RTPs for Oregon’s six metropolitan areas are not planning for anywhere near the kinds of reductions in VMT per person that are needed: 18% by the year 2020 and 33% by the year 2035. In a future post, I’ll discuss what these kinds of reductions in VMT per person might mean for Oregon’s transportation system.
Oregon has many great engineers, trained at Oregon State University and elsewhere. Today, if you want to, say, build a highway from Point A to Point B handling × average daily traffic (ADT), the engineers can pull out their “Highway Capacity Manual” and tell you exactly what kind of highway is needed to get from here to there.
Moving forward, a bigger challenge than moving traffic from here to there will be moving from where we are today to a future with far less greenhouse gas emissions. The state’s engineers, including many good people with the Oregon Department of Transportation, need to begin retooling and rethinking to figure out in detail how to solve the challenges of this century, not the last.
But what do you think? The Basic Equation offers a framework for exploring the future. Using it, what kind of future do you see? How do transportation proposals we are hearing fit into this framework, and do the numbers add up?
Framework Part 3: Leadership, Commitment and Accountability
P.S. To learn how some other engineers, in this case from Princeton, propose to re-engineer the future, not only for the transportation sector of Oregon but for the entire world, listen to a National Public Radio story about the “Wedge Game.” In brief, to reduce greenhouse gases worldwide to acceptable levels by the year 2050, it will be necessary to adopt seven specific policy actions—”wedges”—from a menu of 15 possible actions. The first two possible “wedges” relate to transportation: doubling transportation efficiency and halving VMT, i.e., the Technology and Behavior factors we have been discussing.
1 In this age of cheap computers and even cheaper calculators, many might not know what a slide rule is. That’s too bad because the old analog technology offered a simple, concrete, tactile way to learn number sense in a way that the new digital tools don’t. Slide rules made it easy to do multiplication and division—and to see tangibly how the magnitudes of different numbers compare. One could even argue that a lack of number sense underlies the difficulty current society has in facing many important problems.
2 The term “re-engineering” is meant loosely. According to Wikipedia, “re-engineering is the radical redesign of an organization’s processes, especially its business processes. Rather than organizing a firm into functional specialties (like production, accounting, marketing, etc.) and looking at the tasks that each function performs, we should, according to the reengineering theory, be looking at complete processes from materials acquisition, to production, to marketing and distribution. The firm should be re-engineered into a series of processes.”
3 See Figure 11 in Appendix A of the Final Report to the Governor: A Framework for Addressing Rapid Climate Change, Governor’s Climate Change Integration Group, January 2008
6 See Figures 18 and 19 in Appendix A of the Final Report to the Governor: A Framework for Addressing Rapid Climate Change, Governor’s Climate Change Integration Group, January 2008
7 See 2007 Oregon Population Report, Portland State University Population Research Center, March 2008
8 See Forecasts of Oregon’s County Populations and Components of Change, 2000-2040, Oregon Office of Economic Analysis, April 2004
9 “Update 1: US DOT wants autos to average nearly 32 mpg by 2015,” Reuters, April 22, 2008
10 “Guide to Choosing a Vehicle,” Oregon Environmental Council
11 “US hybrid sales up 38 percent in 2007; Prius leads the pack,” Associated Press, April 21, 2008
12 For example, a vehicle traveling 175 miles uses 7 gallons of gas at 25 mpg but only 5 gallons of gas at 35 mpg, a reduction of 2/7 or 29% (not 40%, as one might naively suppose). Mathematically, fuel efficiency and fuel use are inversely related, so raising the fuel efficiency by a factor of 1.4 lowers the fuel use by a factor of 1/1.4 = 0.71, i.e., by 29%.
13 The text of the Transportation Planning Rule is available online. For a history of the TPR, see “The Politics of Implementation: Oregon’s Statewide Transportation Planning Rule—What’s Been Accomplished and How,” by Martha J. Bianco and Sy Adler, November 1998
14 See Table 8, “Summary of Key Performance Measures” in Chapter 4, Central Lane Regional Transportation Plan, Lane Council of Governments
15 If the transportation sector continues to account for 34% of all emissions, then it will need to reduce emissions from 23.8 MMTCO2E/year (= 34% × 70 MMTCO2E/year) to 10.9 MMTCO2E/year (= 34% × 32 MMTCO2E/year), i.e., to 46% of today’s levels: the same percentage as for reducing overall emissions. On the other hand, if the transportation sector grows to account for 50% of all emissions, then it will need to reduce emissions only to 16 MMTCO2E/year (= 50% × 32 MMTCO2E/year), i.e., to 67% of today’s levels. But the flip side of giving the transportation sector a break is that other sectors, which currently account for 66% of all emissions, will need to reduce emissions from 46.2 MMTCO2E/year (= 66% × 70 MMTCO2E/year) to 16 MMTCO2E/year (= 50% × 32 MMTCO2E/year), i.e., to 35% of today’s levels.
16 The Total Emissions factor is (50 MMTCO2E/year) / (70 MMTCO2E/year) = 0.71. We set the Transportation Sector factor to 1, assuming that transportation will continue to account for 34% of emissions. Oregon’s population in 2020 is projected to be roughly 4.35 million people, resulting in a Population factor of (4.35 million) / (3.75 million) = 1.16. Finally, we assume that technological improvements by the year 2020 will result in a 25% reduction in emissions, mile for mile, i.e., a Technology factor of 0.75.
17 The Total Emissions factor is (13.9 MMTCO2E/year) / (70 MMTCO2E/year) = 0.20. We set the Transportation Sector factor to 1, assuming that transportation will continue to account for 34% of emissions. Extrapolating trends, Oregon’s population in 2050 will approach 6 million people, resulting in a Population factor of (6 million) / (3.75 million) = 1.6. Finally, we assume that technological improvements by the year 2050 will result emissions being cut in third, mile for mile, i.e., a Technology factor of 0.33.