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Article Excerpt
Introduction
I. Mobility & Accessibility: Four Policy Levers A. Transportation Infrastructure B. Transportation Pricing C. Transportation Education D. Land Use 1. Density 2. Diversity 3. Destination Proximity 4. Distance to Transit 5. Design II. Accessibility-Based Scenario Planning A. Asking "What If?" B. Land Use-Transportation Scenario Planning III. Federal Transportation and Environmental Mandates A. Long-Range Systems Planning 1. Transportation Planning Statutes 2. Transportation-Air Quality Conformity B. Project-Level Planning 1. Alternatives Analysis 2. Indirect Impacts Analysis Conclusion
INTRODUCTION
U.S. cities are a major contributor to greenhouse gas emissions. Collectively, the commercial and residential buildings that make up our urban areas contribute 38% of the nation's human-generated carbon dioxide emissions and urban-related car and truck travel another 21%. (1) And yet, American cities are a significant source of hope in the battle to reduce climate change impacts. True, American culture, policy, and affluence have created some of the most resource consumptive landscapes in the world, (2) but the picture is not uniformly dismal. In carbon emissions, as in real-estate, not all urban development is equal.
In fact, there is substantial variation in the resource consumption and carbon emission capacity of differing development patterns. Manhattan, for example, has been labeled one of the nation's "greenest" places, in part because of its record of energy efficiency in transportation, (3) while Raleigh-Durham has been identified as one of the most resource consumptive. (4) While it is tempting to label these variations as just another dimension of the city-suburb continuum, that would be too simplistic and conclusory. Moreover, it would not offer much in the way of guidance for future action. Instead, what is needed is a framework that first provides some understanding of how people interact with their built environments and then offers constructive direction for policy development.
This Article attempts to construct that framework. Part I begins by outlining the elements that should be included in the framework, using the concept of accessibility as the primary organizing structure. Part II describes how the framework might be made operational through the use of an emerging technique called land use-transportation scenario planning, and offers some indication of what deployment of that technique might mean for reductions in carbon emission rates. Part III then assesses how well land use-transportation scenario planning fits within the dictates and limits of U.S. environmental and transportation law.
The analysis reveals that accessibility-based land use-transportation scenario planning holds substantial promise as a decision-making tool that could lead to meaningful cuts in carbon emissions. While the technique is accommodated by several important federal environmental and transportation statutes, the fit is awkward. Moreover, the degree to which federal law mandates use of the technique is limited, indicating that its wide-scale deployment will likely also be limited. Given this outcome, the Article concludes that national leadership is needed for the development of statutory revisions, principally in the federal transportation planning and funding law, which is scheduled for renewal by Congress in 2009. (5)
I. MOBILITY & ACCESSIBILITY: FOUR POLICY LEVERS
Patterns of land use and transportation investment that are carbon profligate can be differentiated from those that are carbon efficient by whether the pattern was designed and built to prioritize mobility, on the one hand, or accessibility, on the other. Strictly speaking, mobility focuses on the movement of vehicles in time and space. (6) Accessibility, by contrast, focuses on the ease and convenience by which a person (or an increment of freight) can gain access to a needed activity. (7) While the two concepts are related, they are not mutually dependent. (8) In many circumstances increased mobility can increase a person's level of accessibility to daily destinations. (9) Assuming a constant geographic arrangement of destinations and low levels of traffic congestion, the number of places one can access in a car is frequently much greater than the number accessible by walking. (10) Accessibility, however, is not dependent on mobility. (11) For example, a person's access to grocery shopping can be increased by the construction of a new store within walking distance of that person's home or place of work. This would result in a net increase in the person's accessibility in a way that is independent of mobility. In fact, the person's expressed amount of mobility would likely decrease. Assuming households in Manhattan and Raleigh-Durham have roughly equivalent needs for access to basic daily activities, (12) Manhattanites accomplish the same tasks with substantially less mobility than those living in Raleigh-Durham. (13)
Given the environmental and climate impacts associated with increased levels of mobility, (14) it would seem that the focus of land use and transportation planning, policy, and investment should be on accessibility. This, sadly, is not the case. Instead, for the past half-century, those efforts have been directed, almost exclusively, at reducing impediments to, and thereby increasing, mobility. (15) The operative principles that lie behind this seeming obsession with mobility can be grouped into four basic policy "levers": transportation infrastructure, transportation pricing, transportation education, and land use. (16) These policy levers, which individually and synergistically influence individual travel choices and community level transportation patterns, have been pointed, almost uniformly, toward mobility-based outcomes since the mid-twentieth century. Hence, moving toward an accessibility-focused, and more carbon-efficient, land use and transportation planning framework will require substantial readjustment to each one of the levers.
A. Transportation Infrastructure
The impact of transportation infrastructure on travel demand is rooted in the physical requirements of public investment to facilitate movement-one cannot drive on a road that does not exist. The presence of transportation infrastructure does much more than facilitate trips, however. It can, in fact, influence the timing, length, destination, and mode of a trip, or whether a trip is made at all. Although for decades transportation planning has been based on the assumption that the amount of demand for travel is set predominantly by demographic forces, it is now understood that demand also responds to the amount and nature of the supply provided. According to "Down's Law," demand for travel expands to fill the capacity provided to it. (17)
When a new or expanded facility adds significant amounts of capacity to a transportation system that formerly was near or beyond its capacity, travel on the new/expanded facility is easier and quicker compared to other travel options, at least initially. Because people, to a large degree, make travel choices that optimize for speed and convenience, (18) they are apt to change their behaviors to take advantage of the new capacity. Those behavioral changes express themselves in short-term shifts in daily travel patterns, medium-term changes in trip frequencies and lengths, and longer-term structural changes in land development patterns. These three phenomena are referred to, respectively, as triple convergence, induced travel, and induced development.
As the name implies, triple convergence connotes three ways in which travelers take advantage of a new or expanded transportation facility: by changing their time of travel, their travel mode, or their travel route. (19) All three describe responses to the new or expanded facility's increase in relative speed and convenience, compared to other travel choices. The temporal shifts occur among travelers who formerly avoided rush-hour congestion by traveling at other times; the new/expanded facility allows these travelers to change to traveling during the peak period. Travelers who formerly used modes of travel other than the one improved by the capacity expansion are similarly induced to switch to the improved mode. Travelers using other, parallel routes will likewise be encouraged to switch to the improved facility. (20) Together, these three short-term adjustments to travel patterns converge to soak up substantial amounts of the new capacity offered by the new or expanded facility. (21)
Induced travel describes the changes people make in trip frequency and length in response to transportation capacity increases. One might assume that as travel becomes faster, people would use the time saved toward some other productive activity, but this, largely, is not the case. Basic economics teaches that as a product becomes less costly, people tend to consume more of it. (22) So it is with travel. When the cost of travel decreases, in this case as measured by time, people tend to do more of it. (23) This occurs, despite the fact that travel is a "derived demand"--in other words, it is not a good in and of itself but a function that provides the means for obtaining goods or accomplishing tasks. (24) It is now understood that people have a daily "travel time budget"--an amount of time that they are willing to devote to traveling each day. For most people, that budget is somewhere around seventy-five minutes, regardless of travel conditions. (25) As average travel speeds increase or decrease, people make proportional changes to their trip-making behaviors to stay close to their travel time budget. Hence, as travel speeds increase due to a significant capacity expansion, many people respond by increasing their trip frequencies and lengths, particularly for discretionary trips such as shopping. (26) For example, they begin making individual trips to stores they formerly visited as part of multi-destination tours--thereby increasing the rate at which they make trips--and they select stores further away than they did previously, adding to their average trip distances. These relationships are demonstrated graphically, and somewhat cynically, by the cover of the April 1966 edition of Asphalt magazine (see Figure 1).
[FIGURE 1 OMITTED]
Induced development (sometimes called induced growth) refers to the long-term changes in land use patterns resulting from significant capacity expansions, reflecting shifts in the origins or destinations of trips. (27) Consistent with the total travel time budget outlined above, average travel times for various trip purposes (for example, work, school, and shopping) have remained relatively stable for decades, perhaps even for centuries. (28) This has been especially true for commute trips. Throughout the last third of the twentieth century, average commute times remained steady at approximately twenty to thirty minutes. (29) Yet, during the same period, travel speeds increased appreciably, reflecting increases in travel capacity. (30) Obviously, this meant that travel distances also increased. While in some cases the increased commute distances reflected shifts in workplace location, they more often reflected shifts in housing location, with commuters choosing to trade the increased travel speeds for more distant, and frequently larger, residences. (31)
Adding or expanding a transportation facility usually also means increasing the potential traffic flow in the vicinity of the improvement, thereby increasing the number of people who can access those places--in other words, more people can now travel to those locations within a given time frame. (32) This increased access enhances the market attractiveness of those locations. (33) For example, major retailers prefer highly accessible sites, as do businesses that rely on high levels of access to labor markets. The increased attractiveness, however, is relative: the locations served by the new or expanded facility have increased accessibility compared to other potential locations within a given market area. This means that the newly favored locations gain a competitive edge over the others. In time, this is likely to manifest itself through additional land development in the areas surrounding the improved facility. (34) The new or expanded facility does not create the demand for the new development, per se--in most cases the development would have occurred somewhere in the market area anyway. The new facility does, however, influence the location of the development, proximate to the expanded facility. (35) This new development, of course, will have a certain amount of travel associated with it. Depending on the development's size and type--commercial, residential, or industrial--the impacts of the added trips on surrounding transportation networks--including the newly expanded facility--could be substantial.
In the context of new or expanded highways, triple convergence, induced travel, and the travel generated by induced development conspire to swamp the additional capacity provided by a new or expanded facility. (36) The extent to which these factors consume that capacity depends on a number of site-specific factors, particularly how congested the pre-existing roads were before the expansion. Studies estimate that the short-term effects could consume 40-50% of the new capacity: (37) "the longer-term effect is likely to be greater, with a higher proportion (perhaps all) of the time saved being used for further travel.'' (38) In other words, depending on local conditions, approximately half of the new capacity could be consumed by triple convergence and much of the rest consumed by the impacts of induced travel and induced development. (39)
Interestingly, these same relationships between supply and demand appear to apply to all transportation modes, not just to highways, although not to the same degree. (40) For example, when the Utah Transit Authority added light rail service to its system for the first time in 1999, overall transit rider-ship increased 17% in just one year; an additional 9% increase occurred in the year after the agency opened its second line in 2001. (41) Similar effects have been observed for non-motorized travel as well. (42) The effects in nonautomobile contexts arise from the same factors observed with respect to highways: the added capacity provided by new or expanded facilities makes travel by those modes more attractive because of actual or perceived increases in speed or convenience.
As outlined, the provision of transportation supply through investments in infrastructure can significantly affect the choices travelers make in how, when, where, how often, and how far they travel. Rather than being fixed and pre-determined solely by demographic influences, demand tends to follow supply to a certain degree, lending credence to those who argue that regions cannot successfully build their way out of congestion. (43) In the end, people tend to make rational choices that maximize the time and convenience efficiencies of their travel. If public policy and investment decisions make traveling in a certain method superior to other options, people will gravitate to that method. Since the 1950s, U.S. policy and investment decisions have made automobile driving the superior method (44) and people have responded by dramatically increasing their level of driving. (45) The increase in driving has been attended, of course, by commensurate increases in carbon dioxide emissions. (46)
The increased mobility that occurred as a result of these investment policies initially facilitated increased accessibility to a wide range of destinations. Over time, however, levels of accessibility steadily eroded. Through the effects of induced development, increased mobility has facilitated a steadily expanding development pattern. (47) The saturation of automobile-related infrastructure and corresponding automobile dependency within dominant segments of American society have helped lead to a dispersion of destinations, thereby increasing the distances between where people are and where they need to go. In a self-fulfilling way, this has made access to many destinations increasingly dependent on high levels of mobility, frequently achievable only by the automobile. (48) These mobility levels, however, are not shared across society (49) and they are increasingly difficult to maintain fiscally and environmentally. (50) Even within the portions of society that own and drive cars, destinations within a constantly dispersing development pattern are becoming less accessible because of increased distances (51) and higher levels of automobile congestion. (52)
To reverse these trends and move toward an accessibility focused planning process, the transportation infrastructure policy lever needs to shift substantially away from investments in highway expansion and toward non-highway investments that support a greater concentration of activities. (53) Instead of obsessing on the need to ease or increase the flow of vehicles, transportation planning should refocus on facilitating accessibility to needed and desired activities. In other words, attention needs to shift from the needs of the machine to the needs of the operator. (54)
B. Transportation Pricing
People tend to make their travel choices in response to perceptions of cost (55)--in transportation, as in other areas of life, people look for bargains. It is not just the total cost of transportation that is influential, however, but also whether those costs are fixed or incremental. Fixed costs are those that do not vary with the amount of use. One either pays the cost--thereby gaining access to a particular travel option--or does not--resulting in the foreclosure of that option. Examples include the capital cost of buying a car or the cost of buying a monthly bus pass. In both cases, the amount of cost and the amount of use are unrelated, with neither affecting the other.
With incremental costs, on the other hand, costs and use are proportional: the more you use, the more you pay. Here, the best example is a bus fare. Every time someone boards the bus, they pay a fare (assuming they do not have a pass). Other examples include highway tolls, parking (at meters or pay lots), fuel, and the exertion of pedaling a bicycle. Time and convenience costs are incremental, as well: the time spent sitting in traffic congestion or trolling for an on-street parking spot are paid per instance.
The basic rule is that people seek to maximize the use of transportation modes that are based predominantly on fixed costs and minimize the use of incremental cost options. (56) From a personal utility perspective, this makes sense. (57) The fixed-cost option is already paid for; using it more will not cost more. (58) In fact, increased use of a fixed-cost transportation option lowers the calculated amortized per use cost of that option, often to the point where continued use is perceived to be free. (59) In contrast, an incrementally charged option will, by definition, always cost more with additional use. Hence, travelers that have comparable fixed cost and incremental cost alternatives will almost always chose the former over the latter. (60)
On balance, most of the costs associated with car ownership and use are fixed. Of the $835.6 billion Americans spent on owning and operating private automobiles in 2001, 53% was spent on fixed costs--purchase price, financing, insurance, licensing, and registration--while only 20% was spent on incremental costs--fuel and tolls. (61) Although some time and convenience costs associated with car use, such as those associated with traffic congestion, are paid incrementally, these costs are generally offset by the automobile's many time and convenience benefits, which also accrue incrementally.
By contrast, many of the costs associated with transit use are imposed incrementally. As mentioned, with the exception of monthly passes, fares are generally charged on a per use basis, which is by definition an incremental cost. In addition, transit travel tends to be significantly slower than automobile travel, (62) with much less geographic and temporal flexibility. These time and convenience costs are also paid incrementally.
Given these conditions, a casual observer would have to conclude that U.S. transportation policy either favors driving or is indifferent: well over half of the costs of driving are paid through fixed-cost methods, whereas the costs of using non-automobile modes, in both out-of-pocket and time costs, are paid incrementally. Intentional or not, the current transportation pricing methods are partially, but significantly, responsible for America's automobile dependency (63) and its resulting dispersal of destinations and decrease in accessibility....
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