LAND USE - TRANSPORTATION INTERRELATIONSHIP September 12, 2002
History has shown that urban areas in the United States have evolved from small towns to larger ever-expanding metropolitan areas. Transportation also evolved during this time from simple walking to the speed of the jet plane. The general consensus by academia is that land use and transportation have had strong impacts on each other throughout this evolution. What is unclear is the level of their interrelationship for future planning. Although recent evidence appears to show that these impacts are weaker, planners can still have a significant effect in guiding land use and transportation development in the complex urban environment by taking a comprehensive and rational approach.
Cities exist due to the fact that it is convenient for people to aggregate. J.S. Adams (1970) identified four transportation-related eras in the United States. Significant urbanization began in about the mid 1800s with the Industrial Revolution. Prior to this time urban areas were clustered in sizes that were no larger than what it would take to walk 30 minutes in a radius from the center. This walking distance expanded later to about 45 minutes. This characterized the beginning of the Walking-Horsecar Era of 1800-1890. In the 1830s, railroad construction allowed travel or commuting to the cities from suburbs that were created along these transportation routes. This primarily served the affluent population. At about the same time intracity mass transit had its beginnings with omnibus lines and the horse-drawn streetcar which rode on rails. The moderate increased transportation speeds created a rapid proliferation of middle-income residential development at the city's edge. Lower-income residents could not afford to move farther out and remained clustered in high-density locations next to industrial areas in the inner city. The downtown central business district (CBD) came into being by the late 1800s when it was apparent that it was most convenient to locate retail, commercial and other services at this centralized location.
The Electric Streetcar Era of 1890-1920 increased intraurban travel speeds to about 15 miles per hour and created further expansion of the city's perimeter to a distance that could be reached within about the same 45 minute time frame. These streetcar lines radiated out from the city center similar to spokes on a wheel. Stores were built along these lines while residential development fanned out from them. The most significant effect of the electric streetcar was that it allowed the large number of blue-collar workers and their families to congregate in their own ethnic neighborhoods as opposed to the tenements next to the industrialized eras.
The Recreational Automobile Era of 1920-1945 caused further population decentralization. Although the depression was a limiting factor development was created that filled in the gaps left between transit routes. A circular shape to the urban metropolis was formed and the edges of the city became more independent from the CBD. It was during this period that the automobile began to create hardship for urban transit. Home builders had subsidized streetcar companies so that people could be transported to their developments. These subsidies stopped with increased automobile use and transit routes began to deteriorate. Other related factors were the dispersal of population away from transit lines and dispersion of industrial entities and other employment sites away from the central city. These early trends greatly increased during the Freeway Era of 1945 to the present when the automobile came to dominate transportation and increasingly affected land use. A massive highway construction period was stimulated by the 1956 Interstate Highway Act. These high-speed limited access expressways were similar to the aforementioned transit routes in that they radiated out from the city center. In addition, circular expressways or beltways were built that went around the metropolitan areas. Together, these expressways greatly accelerated land use changes along their routes in the form of residential and industrial development. This development increased the metropolitan perimeters substantially. Urbanites are now able to live much farther from their employers. Major highway intersections of the outer city have spawned concentrations of business, retailing and light industty that have parity with each other as well as the nearby central city CBD. 
R.M. Haig (1926) argued that, in a monocentric city, "transportation costs and site rents are vitally connected through their relationship to the friction of space." People will obtain the most desired locations through their willingness to pay for higher transportation costs. Therefore, an improvement in the transportation system will cause a drop in land values throughout an urban area and cause the city to expand outward (expansion of "market shed" and "commute shed") depending upon the elasticity of demand for transportation. High income individuals are more likely to pay higher rents for larger suburban locations while those with low-incomes are more likely to pay higher rents for smaller inner area locations as they cannot afford the transportation costs.  This was demonstrated in Hotelling's Linear City (1929) which shows that the optimal number of markets is a tradeoff between transportation costs and market setup costs. As transportation costs decline the optimal size of the market shed increases. 
Genevieve Giuliano (1995) states that it is difficult to measure the level of influence transportation investments have on forming and influencing land use patterns as they are jointly dependent. Land use form or the location of activities is affected by accessibility or the ease of moving from one place to another. In turn, transportation or travel patterns are affected by land use characteristics. Theories of transportation and land use interaction focus on economic-behavioral factors. Profit maximization and utility influence land use and location choice. Land apportionment is determined by production costs which includes the costs of transportation. Theories also focus on mathematical programming models in three variations: maximization of
transportation movement for a set allocation of land use activities; allocation of land use activities for a given, fixed set of transport costs; or allocation of land use activities for a given set of transportation characteristics. 
Giuliano further states that standard urban economic theory evolved to explain the basic structure of cities in terms of their land value and population density patterns. The theory is centered on residential location choice and assumes logical behavior, identical preferences, and flawless data. In addition, it is assumed that: the city center holds all employment; each household has only one worker and only work travel is weighed; housing is a function of capital and land, thus location and lot size are the distinguishing factors; and unit transportation cost is steady in all directions, and includes time and monetary costs.
The city is structured with population density and land values highest in the center. These values decline with increased distance from the city center. Households are dependent upon factors such as land, commuting costs, and other costs in seeking utility maximization. Both standard economic and rent gradient theory predicts that as transportation costs decline population decentralizes and moves away from the city center and more housing will be consumed. The ideal location for a particular household is that point at which the increase in transportation cost is just offset by the savings in housing.
Generally, inductive evidence supports the standard theory that population is most dense in city centers. In addition, there is a correlation between declining population densities with improvements in transportation systems. However, if the direct correlation between housing costs and transportation costs is relaxed and more preference is given to housing then even more housing will be consumed at the cost of additional commuting. There is some
supporting evidence that this is actually true. Therefore, higher-income households would locate farthest from the city center while lower-income households would consume less housing and locate closer to the city center.  Today's geographic patterns of urban land use and travel
demand were strongly influenced by the historical developments in transportation, however, travel behavior has only been influenced by land use to a limited extent. Future investments in transportation will have even more of a limited effect on urban land development and land use.  The reason being that it is inherently difficult to change the built environment once it is in place. Additionally, there is little funding available for system expansion as governments have been unable to maintain state of good repair in recent years. Rapid expansion of the limited express highway system in the 20th Century substantially accommodated and induced travel demand of personal vehicles that previously was very small. New transportation expansion projects make up smaller proportions of the urban environment over time.
As described by Adams, the growth of the urban edges at a faster rate than the already developed interior, has been the result of over two centuries of intraurban transportation innovations and the development patterns they formed culminating with the increased use of the automobile in the freeway era of post World War II. Building of transit lines in many major cities has not resulted in significant increases in ridership. A main reason is that transit lines cannot serve a substantial level of transportation needs in the low density automobile oriented suburban areas. Many of the recent transit lines have followed the traditional CBD-focused, hub-and-spoke network which has become increasingly irrelevant. The implications in urban transportation planning lie in moving people about these downtown-type independent dispersed, polycentric centers within metropolitan areas. More expressways do not appear to be the answer as they seemingly create more traffic gridlock as in cities such as Los Angeles and Houston.  Other cities with less developed expressways have been able to increase transportation efficiency. This approach has slowed reductions of development clustering which enables better mode choice and lower travel costs.
Studies of the impacts of transportation investments on land use have shown mixed results. Transportation system impacts are just one of many other factors that influence land use. In addition, the interaction of transportation and land use takes place over many years due to the longevity of capital infrastructure and the market response to changes. The postwar Interstate highway construction boom predominantly took place from the mid 1950s into the 1980s when most of it was completed. Any subsequent highway investment is only a sma!I portion of the much larger urban transportation network and will consequently have limited impact. The amount of developable land is also a determining factor in the impact of a highway investment. Local zoning codes may not aliow significant change or development. In addition, if the area economy is slow then little impact could be expected from the investment. The scale of analysis is also a factor in terms of whether to study the impact on only the immediate vicinity or the region as a whole. Finally, analysis should be meticulous in distinguishing what the general economic growth and land use change would have been without the impacts of highway investments given circumstances with growing regions in many areas of the country in the 1980s. 
In recent years, there has been a lack of land use impact studies of highways as there have been little new highway construction and a lack of funding for such studies. The DOT Beltway Study published in 1980 was performed by the U.S. Department of Transportation to look at land use and related impacts of beltways (Payne-Maxie Consultants, 1980). It was found that the land use impacts of beltways have mostly been insignificant. The study found that the existence, location and length of a beltway had no consistent effect on growth. When economic conditions were favorable, manufacturing and retail activities located along beltways while the distribution of employment growth between suburb and central city was not significantly different for those cities without beltways. The central-city residential population had more growth in those cities where the beltway was located within the city as opposed to its location in the suburbs. In addition, those cities without beltways had the most suburban residential growth. "The Study authors conclude that the extent of land use impacts is determined largely by market conditions. When conditions are favorable, land use change will occur, and when conditions are not favorable, land use change is unlikely." 
Studies have shown that rail transit by itself has not had systematic impacts on land use in the post-World War II era. However, by coordinating transit plans with other provisions, greater land use impacts can be realized. Such provisions include: coordinating transit plans and local land use at the regional level; complimentary parking and traffic policies; public infrastructure to support development; and financial incentives to attract development in the vicinities of transit stations. It also appears that the interdependence between transportation and land use will continue to decline with the emergence of increased telecommunications. 
The proliferation of low-density development and decline of CBDs has increased the importance of a balanced street system to serve the amount of trips and varying types of trips that occur in a metropolitan area. Such a street system should emphasize the importance of principal and minor arterials to support travel amongst densely populated areas and major activity centers. Analysis of vehicle-miles of travel (VMT) has shown that arterial and freeway systems carry approximately 70% of total traffic."  Efficient bus service needs to be encouraged for these types of trips so that low-income individuals who may not be able to afford an automobile will not be at a disadvantage.
Some have theorized that transportation in the United States is dominated by three modes of transpotiation: walking, automobile and airplane. Substantial evidence has shown that a person's choice for a trip is based on travel time, cost and, subconsciously, distance which is associated with time. People have been very willing to spend more for high speed transportation because of the preference of high speeds over lower speeds. However, analysis has shown that the demand for speed hinges on the distance traveled. Transportation gaps are created in instances where distances may be too far to walk but too short to use an automobile efficiently without causing or contributing to traffic gridlock, pollution, and higher user costs. The answer may be spatial reorganization and/or increased telecommunications.  In addition, walking and bicycling should be encouraged by creating compact, pedestrian friendly development including sidewalks and bicycle lanes. Transportation gaps may also be apparent for longer distance trips where the distance is too far to travel by automobile efficiently and too short to fly by airplane economically. A gap of this type could certainly be achieved through high-speed rail which is virtually nonexistent in the United States. The shut down of the air transportation system on September 11, 2001 demonstrated this gap as thousands of travelers were stranded without efficient transportation altematives. Continued high consumption of non-renewable energy resources also warrants closer evaluation of such transportation gaps. An energy crisis could restrict the unlimited travel by automobile that has been enjoyed in the United States for many years. Such a scenario of increased transportation costs would create smaller market sheds and commute sheds. In association, there would be higher population densities nearer CBDs and the mini CBDs that have been built around transit stations and arterial junctions in the suburbs. Rational investments that have been made in transportation structure will have an impact on creating more efficient land use pattems.
1. J.S. Adams, Residential structure of Midwestern cities. Annals of the Association of American Geographers, 60, 37-62, described in Peter 0. Muller, Chapter 2: Transportation and Urban Form: Stages in the Spatial Evolution of the American Metropolis. University of Miami. Contained within The Geography of Urban Transportation (Hanson, ed.) (New York: The Guilford Press, 1986), 26-47.
2. R.M. Haig, Towards an understanding of the Metropolis, Quarterly Journal of Economics, 40, 179-208, described in K. Button, Transport and Economics. 2'' Ed. (Eiger; 1983), 30-32.
3. Hotelling's Linear City, 1929, as described by Kazuya Kawamura, Urban Planning and Policy, UPP560, Urban Transportation Planning 1: Introduction, lecture, September 5, 2002.
4. Genevieve Giuliano, The Geography of Urban Transportation (New York, NY: The Guilford Press, 1986), 306-307.
5. Ibid, 310-311.
6. Don Pickrell, Chapter 12: Transportation and Land Use in Essays in Transportation Economics and Policy (Gomez,-Ibanez, Tye, and Winston, ed.), (Brookings Institution Press, Washington D.C. 1999), 431-432.
7. Muller, 46-50.
8. Giuliano, 327-330.
9. Payne-Maxie Consultants, The land use and urban development impacts of beltways. Final Report No. DOT-OS-90079, US. Department of Transportation and Department of Housing and Urban Development. Washington, D.C.: Payne-Maxie Consultants, 1980, in Giuliano, 330-332.
10. Giuliano, 335-338.
11. Khisty and Lall, Chapter I: Transportation as a System in Transportation Engineering: An Introduction (Prentice Hall, 1999), pp 15-17.
12. Ibid., 18-21.
Adams, J.S. Residential structure of Midwestern cities. Annals of the Association of American
Geographers, 60, 1970.
Button, K. Transport and Economics (2"d Ed.), Elger, 1983.
Giuliano, Genevieve. Chapter 13: Land Use Impacts of Transportation Investments: Highway and Transit in The Geography of Urban Transportation (Hanson, ed.), New York: The Guilford Press, 1986.
Hotelling's Linear City, 1929.
Khisty and Lall. Chapter 1: Transportation as a System in Transportation Engineering: An
Introduction. Prentice Hall, 1999.
Muller, Peter 0. Chapter 2: Transportation and Urban Form: Stages in the Spatial Evolution of the American Metropolis in The Geography of Urban Transportation (Hanson, ed.), New York: The Guilford Press, 1986.
Payne-Maxie Consultants. The land use and urban development impacts of beltways in Final Report No. DOT-OS-90079, U.S. Department of transportation and Department of Housing and Urban Development. Washington, D.C.: Payne-Maxie Consultants, 1980.
Pickrell, Don. Chapter 12: Transportation and Land Use in Essays in Transportation Economics . and Policy (Gomez,-Ibanez, Tye, and Winston, ed.), Brookings Institution Press, Washington D.C. 1999.