Office of Planning, Environment, & Realty (HEP)
This report was superseded in October, 2011.
As the United States is faced with escalating global competition and the associated rapid increase in international trade and freight movement, it is becoming critical to support economic development by enhancing the capability and capacity of transportation infrastructure. (American Association of State Highway and Transportation Officials (AASHTO), 2007).
However, transportation statistics indicate that the current U.S. transportation infrastructure is not sufficient to support these trends. While the number of vehicles and vehicle-miles of travel increased by 39.8% and 81.2%, respectively, road and street mileage increased only 2.4%. The annual vehicle-miles of travel on interstate highways increased by 39.4% between 1990 and 2000, while the miles of interstate highways increased only 3.6% during the same period. In addition, as population and economic growth has concentrated on urban areas, the annual vehicle-miles of travel increased more in urban areas (30.6%) between 1990 and 2000, compared to rural areas (24.9%). Specifically, for interstate highways, the annual travel-miles increased 41.3% in urban areas and 34.5% in rural areas during the same period while the increase of travel-miles on local roads is higher in rural areas (31.0%) than in urban areas (23.5%) (Federal Highway Administration (FHWA), 2000). This identifies the failure of supply of the infrastructure to keep pace with rapid increase in demands in urban areas during the past several decades. Large metropolitan areas continuously expand from urban areas to urban area sharing transportation networks and environmental systems over large geographic areas making transportation systems difficult to manage by one individual metro region. Such growth pressures environmental resources around transportation infrastructure as well as the fringes of metropolitan areas, calling for construction of green infrastructure as a way to preserve undeveloped land and environmental resources.
AASHTO (2007) emphasizes that the U.S. competitiveness in the global economy can be maintained by preserving the current system of interstate highways, ensuring a modern and efficient transportation system, expanding system capacities, and reducing growth in highway demand by developing alternative modes. At the same time, an effort to protect environmentally sensitive areas and ecosystems from the encroachment of this infrastructure should be made. This suggests the attractiveness of implementing a strategy that directs where and how investment in transportation infrastructure and green infrastructure should be made.
In this section the freight movement, which is not only a key factor for the national economic prosperity but also one of significant contributors to highway congestions, is reviewed within the context of megaregions. Nationwide infrastructure planning is reviewed to examine how national transportation infrastructure planning reflects the current and future necessity to foster and support economic competitiveness. In addition, the role of green infrastructure is examined all under the auspices of megaregion planning.
As much as the efficient passenger travel for inter-metro areas is important in the quality of life and economic competitiveness, the efficient movement of goods via freight transportation infrastructure is essential because freight transportation may significantly affect economic productivity (Jones, 2007). In particular, the transportation infrastructure that connects metropolitan areas to move goods by truck, rail, water, air, and other modes is critical for the nation's economic competitiveness (Puentes, 2008).
A global economy and free trade will increase the demand for movements of goods and services. For example, the volume of shipments is projected to increase to 33.7 billion metric tons in 2035 from 17.5 billion metric tons in 2002 (Jones, 2007). As seen from Figure 3 and 4, the trade between the United States and foreign countries are intensively taking place in most megaregions. In 2005, approximately two-thirds of the total U.S. trade took place in the 50 largest metropolitan areas (Puentes, 2008).
Figure 3: Distribution of the volume of trades with Canada and Mexico (2035)
Figure 4: Distribution of the volume of trades with overseas countries (2035)
To accommodate these future demands, a freight transportation policy that can direct sufficient investment in appropriate areas should be prepared by identifying what kind of transportation modes will be demanded and where those movements will take place.
a) Transportation modes of freight movement
While the volume of shipments is projected to continuously increase, its effects on the transportation system may be different, depending on the transportation modes, the properties of goods, and the characteristics of geographic areas, such as origins and destinations.
The freight transportation system is a complex network of land, water, and air. The Federal Highway Administration's (FHWA) 2006 Freight Analysis Framework (FAF) provides seven modes of transportation, including air & truck2, other intermodal3, pipeline & unknown4, rail5, truck6, truck & rail7, and water8.
Figures 5-7 show that more than half of exporting goods were carried by truck to the ports of exit on the U.S. border. More than 60 percent of domestic commodity flows were moved by truck. On the other hand, the transportation modes of imported goods from foreign countries are distributed more evenly across several modes. For example, approximately 40 percent and 25 percent of imported goods from Canada and Mexico were carried by pipeline and rail, respectively, to the U.S. destinations while 30 percent were moved by truck.
The figures also show that megaregions relied more on truck than non-megaregion areas for freight movements. This issue will be discussed in the next section.
Figure 5: Transportation modes for the domestic trade goods
Figure 6: Transportation modes for the international trade goods with Canada and Mexico
Figure 7: Transportation modes for the international trade goods with overseas countries
b) Domestic commodity flows
More than half of commodities were carried by truck (64 percent) between domestic origins and destinations in 2002. Pipeline & Unknown mode contributed 21 percent, rail 10 percent, and water 3 percent (Figure 5). Specifically, more than 77 percent of commodities from megaregions were moved to domestic destinations by truck in 2002, and its portion in megaregions is projected to 80 percent in 2035, while non-megaregion areas rely less than 60 percent on truck in both 2002 and 2035 (Table 1). This means that megaregions will experience heavier freight traffic on highways than other non-megaregion areas.
Only 4-5 percent of commodities are carried by rail in megaregions, compared to 13 percent of rail usage in non-megaregion areas. Pipeline is highly used in non-megaregion areas (approximately 26 percent in 2002), compared to 4 percent in megaregions.
Table 1. Transportation modes for exporting goods to domestic destinations between megaregions and non-megaregion areas
|2002 (%)||2035 (%)||2002 (%)||2035 (%)|
|Air & Truck||0.02||0.04||0.01||0.02|
|Pipeline & Unknown||14.01||11.97||25.74||26.03|
|Truck & Rail||0.19||0.20||0.21||0.22|
Source: reorganized from the data of Freight Analysis Framework (FHWA, 2006d)
Table 2 also shows that more increase in exporting commodity flows by truck and rail will take place in megaregions than other areas while the increase in the use of the pipeline and water modes is projected to be larger in non-megaregion areas by 2035. However, for importing goods from other domestic regions, there is no significant difference between megaregions and non-megaregions except for the pipeline for which use will increase more in non-megaregions.
The average distance covered by truck freight is shorter (485 miles) than air (973 miles), rail (902 miles), and coastwise water (1,269 miles). Moreover, more than 65 percent of the tonnage of the freight movements by truck is estimated to move less than 100 miles (Puentes, 2008). The relatively short length of trucking implies that the freight movement policy between metropolitan areas at the megaregion level would be useful in relieving congestion caused by truck traffic on highways and to ensure just-in-time delivery of goods.
Table 2. Comparison of growth rates of domestic commodity flows between megaregions and non-megaregion areas (%, 2002-2035)
|Megaregions||Other areas||Megaregions||Other areas|
|Pipeline & unknown||68.7||88.5||68.9||91.6|
Source: reorganized from the data of Freight Analysis Framework (FHWA, 2006d)
c) Commodity flows from and to overseas countries
Table 3 shows how different transportation modes move export and import goods between origins or destinations and ports within the United States. For export goods, the reliance on truck in megaregions may increase from 63 to 74 percent between 2002 and 2035 while the reliance on water, rail, and pipeline may decrease. Although the freight movement by truck will increase in non-megaregions as well, other transportation modes, such as water (16 percent), rail (20 percent), and pipeline (8 percent), are expected to serve many portions of freight movements in these regions.
For import goods, 'Pipeline & Unknown' mode plays significant role next to truck in both megaregions and non-megaregion areas. For example, approximately 37 percent of commodities are moved by this mode in megaregions, and 48 percent in non-megaregion areas. This may be probably because of the characteristics of imported goods, such as oil and natural gas. However, the reliance on truck may increase to 72 percent in megaregions by 2035 while the use of the 'Pipeline & Unknown' mode may decrease from 37 to 21 percent during the same period (Table 3).
Table 4 shows that the volumes of both export and import from the trade with foreign countries will increase more in megaregions by 2035. During this period, megaregions' export goods may increase by 134 percent and import goods by 124 percent, while non-megaregion areas' export goods may increase by 85 percent and import goods by 76 percent. This implies that megaregions may play a more significant role in the nation's economic competitiveness over the next few decades.
This table also shows that the freight movement by truck will increase significantly in megaregions (almost twice the amount of increase in non-megaregions for imported goods) between 2002 and 2035. Although trucks are responsible for the greatest share of U.S. freight movements, the freight rail network also makes important contributions. For example, the rail network is estimated to reduce 100 billion truck miles of travel over the next 20 years (Puentes, 2008).
Thus, in order to mitigate the congestion of freight movements on highways, the investments in alternative modes, such as the rail freight network in megaregions should be considered
Table 3. Transportation modes commodity flows from and to foreign countries
|Megaregions||Other areas||Megaregions||Other areas|
|Air & Truck||0.06||0.12||0.07||0.10||0.06||0.09||0.08||0.11|
|Pipeline & Unknown||7.93||4.49||12.68||7.50||37.48||21.44||48.14||37.96|
|Truck & Rail||1.64||1.36||0.42||0.61||0.13||0.15||0.09||0.12|
Source: reorganized from the data of Freight Analysis Framework (FHWA, 2006d)
Table 4. Comparison of growth rates of commodity flows from and to overseas countries between megaregions and non-megaregion areas (%, 2002-2035)
|Megaregions||Other areas||Megaregions||Other areas|
|Pipeline & unknown||32.7||9.3||28.2||38.7|
d) Conclusions and implications
As a result of the global economy and free trade, many portions of international trade as well as domestic trades are taking place in megaregions. While the freight transportation system includes a complex network of roads, rail, water, and air, more than half of exporting goods were moved by trucks in 2002. This trend is estimated to be reinforced over the next few decades.
The reliance on trucking is higher in megaregions than non-megaregions. The congestion caused by truck traffic on highways may negatively affect economic productivity, increasing the costs of goods movements and generating problems for production schedules. Since these trends are estimated to continue or to be even worse in the future, a strategic approach to the freight transportation infrastructure in megaregions, focusing on highways and alternative modes, such as rail should be considered.
In order to prepare a strategy to effectively face with these challenges, the demands of freight movements, the types of infrastructure that efficiently meet those demands, and the geographic areas where those demands will increase should be studied by analyzing the characteristics (e.g. commodity groups) of goods and their possible transportation modes for each megaregion. For example, approximately 75 and 23 percent of imports/exports (in value of millions of dollars) via Detroit Combined Statistical Area in 2002 were moved by truck and rail, respectively, and 54 percent of them include motorized and other vehicles (including parts) and machinery (Yoder, 2006). Thus, many export/import goods transported via the Detroit area, which is included in the Midwest megaregion, are bulky goods, implying that the efficient highway and rail system that distribute those heavy goods from the port of entry or exit is critical in economic vitality in the region. Importantly, it begs the issue of what kind of conveyance might be more efficient in reducing emissions.
a) The structure of NHS
The National Highway System (NHS) was required by the 1991 ISTEA. FHWA developed this system in collaboration with the states, local governments, and MPOs. The NHS was approved by Congress in 1995. The NHS consists of the Interstate System (IS) and more than 100,000 miles of arterial and other roads (FHWA, 2000). The NHS represents approximately 4% of the total public roads while it accounts for more than 44% of travel. Rural areas have more NHS miles (73.8%) than urban areas (26.2%), but more travel takes place in urban areas (59.6%) than in rural areas (40.4%) (FHWA, 2000). Modifications are frequently made to the NHS which is thus, a living system.
Figure 8 (left). The National Highway System (ESRI, 2006; Bureau of Transportation Statistics (BTS), 2007)
Figure 9 (right). The Strategic Highway Network (STRAHNET) (ESRI, 2006; BTS, 2007)
The NHS is categorized into five parts: the interstate highway system, high-priority corridors (some of which are existing Interstates), the non-interstate portion of the Strategic Highway Corridor Network (STRAHNET), Strategic Highway Corridor Network connectors, and other arterial highways (Slater, 1996). The interstate highway system accounts for approximately 30% (more than 40,000 miles) of the NHS (Figure 8). The high-priority corridors were first identified in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), and there are 80 such corridors as of 2006 (FHWA, 2007). The Strategic Highway Network (STRAHNET) system provides access and emergency transportation of personnel and equipment in times of peace and war. It consists of over 61,000 miles of roads linking major military bases and other defense related facilities to the interstate highway. The almost 2,000 miles STRAHNET connects more than 200 important military bases and ports to STRAHNET corridors (Figure 9).
b) NHS high-priority corridors
The Congressionally-identified high-priority corridors, one of the components of NHS, have been designated with national significance. Beginning with 21 corridors identified by ISTEA in 1991, 59 additional corridors were added in Federal transportation legislation as of 2006 (Figure 10). One of advantage of designation is that these corridors were eligible for funding from the National Corridor Planning and Development (NCPD) Program, a discretionary fund of the U.S. Secretary of Transportation, for planning, construction, and maintenance. The high-priority corridors have been funded through the "ISTEA", "TEA-21", and "SAFETEA-LU" multiyear surface transportation authorizations. While the first two authorizations were effective from 1992 through 1997 and from 1998 through 2003, respectively, SAFETEA-LU is currently effective (FHWA, 2007). SAFETEA-LU did not continue the NCPD. Designation of high-priority corridors may benefit economic development with the improvement of freight and vehicle movement.
c) Highway systems and megaregions
As seen from Figure 8 and 9, an overlapping map of NHS and megaregions9 (RPA, 2006), most urban areas within megaregions are served by or close to interstate highways. However, the capacity and load of roads and streets are different between megaregions and non-megaregions. For example, Table 5 shows that urbanized areas of megaregions have shorter interstate highways and local roads than non-megaregions. Specifically, miles of interstate highways and local roads per 1,000 persons are 0.0586 and 2.6949 for megaregions, but non-megaregions have 0.1075 and 3.8068 miles, respectively. This implies that interstate highways of megaregions are more congested than non-megaregions. Figures 11 and 12 also show that both passenger travel and freight movements are more congested in megaregions.
Table 5. Miles of interstate highways and local roads of federal-aid urbanized areas10
|Total Miles/1,000 persons|
|Urbanized areas of megaregions||0.0586||2.6949|
|Urbanized areas of Non-megaregions||0.1075||3.8068|
Source: reorganized from the table (miles and daily vehicle-miles of travel) of FHWA (2006)
While congressional high priority corridors have increased from 21 to 80 since 1991, some routes within megaregions have not been designated as high priority corridors. They include the routes between Dallas-Fort Worth and Houston (I-45)11 and San Antonio and Houston (I-10) in the Texas Triangle, the route between Houston and New Orleans in Gulf Coast (I-10), the interstate system of central and west Florida (I-75, 4), and the route between Washington D.C. and New York (I-95). Additionally, in the Piedmont Atlantic Megaregion, any route that connects major metropolitan areas, such as Birmingham, Alabama, Atlanta, Georgia, and Raleigh, North Carolina, was excluded from the congressional high priority corridors although these areas have experienced severe congestion in both freight and passenger travel (Figure 11 and 12).
Figure 11 (left). Average daily traffic volumes (National Surface Transportation Policy and Revenue Study Commission, 2007)
Figure 12 (right). Interstate Bottlenecks (National Surface Transportation Policy and Revenue Study Commission, 2007)
Figure 13 presents future interstates on the NHS. Within megaregions, the California Farm-to-Market Corridor, US 59 (Texas), US 90 (Louisiana), US 69 (Michigan and Indiana), and US 41 (Wisconsin) have been designated by Section 1105 of ISTEA as future interstate highways. To incorporate the notion of economic competitiveness in the global economy into the interstate planning and programming process, a megaregions context could be taken into account for designation of future interstates.
a) History of railway systems in the United States
Under the High Speed Ground Transportation (HSGT) Act of 1965, the Federal Railroad Administration (FRA) introduced Metroliner cars and the Turbotrain in the Northeast Corridor (NEC) revenue service in 1969 (FRA, 1997). With the completion of the route between Washington D.C. and New York, the National Railroad Passenger Corporation (Amtrak) led by the Rail Passenger Act of 1970, ensured HSGT options as a part of the intercity rail passenger network (FRA, 1997). With increasing involvement of states as well as federal involvement in HSGT planning during the 1980's, six states, including Florida, Ohio, Texas, California, and Nevada, formed high-speed rail entities although these proposals have not resulted in construction. The High-Speed Rail Transportation Act, of which key issues were reflected in ISTEA of 1991, and the Next Generation High-Speed Rail Technology Development Program in 1994 encouraged study of an implementation of HSGT technologies (Schwieterman & Scheidt, 2007; FRA, 1997). In 2001, Amtrak started Acela Express service, which is the only high-speed railway system that operates at speeds between 75 mph and 150 mph in the United States12. The Acela Express service connects Washington D.C., Baltimore, Philadelphia, New York, and Boston (Schwieterman & Scheidt, 2007).
b) Advantages of HSR systems
As intercity transportation by highway and aviation systems has increasingly suffered from congestion within metropolitan areas due to growing travel demand, many states have invested in intercity passenger rail service (AASHTO, 2007; FRA, 1997). As an alternative to existing surface transportation modes, high-speed rail (HSR) systems have several advantages. First, the use of a HSR system can reduce current congestion in both air ways and highways. Second, the HSR system may save energy (Schwieterman & Scheidt, 2007). National Surface Transportation Policy and Revenue Study Commission (2007) estimates that the railway mode consumes about 17% and 21% less energy per passenger mile than airplanes and vehicles, respectively. Second, HSR emits less carbon dioxide and may contribute to better air quality, compared to airplanes and automobiles. Third, when the HSR system is integrated with existing Amtrak service, it may be possible to provide direct access to downtown areas as well as reducing construction costs (National Surface Transportation Policy and Revenue Study Commission, 2007). Finally, it may be used as a secure intercity transportation mode in the event of future disruptions to the aviation systems as experienced in the September 11 event in 2001.
c) Existing plans for HSR systems
The FRA (1997), conducted benefit and cost analysis of HSR for 8 corridors in the United States. As seen in Figure 14, they include existing corridors where intercity trains currently operate at speeds of more than 110 mph [Northeast Corridor (Boston - New York City - Washington) and Empire Corridor (New York City - Albany - Buffalo)], five potential HSR corridors [Pacific Northwest Corridor (Eugene-Portland-Seattle-Vancouver, B.C.), California Corridor (San Diego-Los Angeles-San Francisco), Chicago Hub (Chicago to Detroit, St. Louis, Milwaukee), Florida Corridor (Tampa-Orlando-Miami), and Southeast Corridor (Washington-Richmond-Charlotte)], and the Texas Triangle (Fort Worth-Dallas-Houston-San Antonio) as a unique "nonlinear" shape. The above five potential corridors were designated under Section 1010 of the ISTEA using operational, financial, and institutional criteria and conditions that existing railroads have the capacity to run at 90 mph.
Figure 14. FRA HSR illustrative corridors (FRA, 1997)
In addition to the 5 HSR corridors under ISTEA of 1991, in 1998, 6 more corridors were authorized as HSR corridors under TEA-21. Since then, the Department of Transportation has designated ten corridors and their extensions (Figure 15).
Figure 15. HSR corridor designations (FRA, 2005)
Recently, the Passenger Rail Working Group (PRWG) (2007), established by Commissioner Frank Busalacchi of the National Surface Transportation Policy and Revenue Study Commission, which was created by Congress, identified the 2050 intercity passenger rail network to estimate the future investment required for the passenger rail system. The corridors, designated by U.S. Department of Transportation, and other corridors, already proposed or expressed as possible developments by states, were overlapped with megaregions (Figure 16). AASHTO (2007) estimated the costs of improvement for 21 intercity passenger rail corridors (Figure 17).
Figure 16. 2050 intercity passenger rail network of PRWG (PRWG, 2007)
Figure 17. Intercity passenger rail corridor development plan (AASHTO, 2007)
Many state and regional agencies have proposed the development of HSR systems. Schwieterman & Scheidt (2007) estimate that about 60% (9991 miles) of proposed mileage in 64 intercity corridors, including corridors included in the above literature are federally designated routes.
d) HSR systems and megaregions
Schwieterman & Scheidt (2007) indicate that about 63% of the proposed mileage for HSR service is included in HSR corridors that cross state lines. All but one of the 43 states proposing routes on the HSR system have at least one interstate corridor slated for consideration. The location of the proposed HSR coincides with the economic core of most megaregions and would serve to provide greater mobility in a more sustainable way. In fact, some corridors, such as the Chicago-Detroit-Pontiac corridor, are divided into several segments reflecting differences in operations and in management/ownership. These segmentations may negatively affect both the development process and future operations in the long run.
Although many corridors connect existing metropolitan areas, each passenger rail route has been identified based on existing transportation patterns and infrastructure and relevant studies (National Surface Transportation Policy and Revenue Study Commission, 2007) without full consideration of future social and economic environments and the global economy. Table 6 shows that about 65.7% of the proposed mileage of 64 intercity corridors, identified by Schwieterman & Scheidt (2007), are located within megaregions and only 40.4% of them are formally designated as federal HSR routes.
Table 6. Share of the proposed mileage of SHR within megaregions and non-megaregions (%)
|Federally designated routes||40.4||20.1||60.5|
Source: reorganized from Schwieterman & Scheidt (2007)
In order to compete globally by enhancing economic competitiveness and maintaining the quality of life in the region, the designation of the HSR network should consider not only financial issues but should include social and economic considerations including complex relationships between the regions.
The elements of transportation infrastructure which facilitate the movement of people, goods and information have created a network of barriers to natural systems. These barriers are in conflict with the natural landscape, impede natural processes, spatially fragment land uses, and isolate open space (Williamson, 2003). Furthermore, the issues of land consumption and environmental degradation are critical in the metropolitan areas because urban sprawl has been a trend in most metropolitan areas with constructions of highways and expanding regional growth. The establishment, planning, and implementation of a "green infrastructure" system may play an important role in offsetting these losses and systematically protecting the ecosystems. Green infrastructure is the ecological framework needed for environmental, social and economic sustainability. These natural networks provide essential ecological solutions that offset impacts created by traditional infrastructure.
a) The concept of green infrastructure
Green infrastructure is a network of open space, woodlands, wildlife habitat, parks and other natural areas that sustains clean air, water and natural ecological processes and enriches our quality of life (Benedict & McMahon, 2002). The concept of green infrastructure repositions open space protection from an amenity to a necessity (Benedict & McMahon, 2002) and encompasses a variety of natural and restored eco-systems and landscape features that make up a system of hubs and links.
Hubs anchor green infrastructure networks and provide origins and destinations for wildlife and ecological processes (McQueen & McMahon, 2003). Hubs include:
Links are the connections between the hubs, facilitating the flow of ecological processes. Links include:
The underlying concepts of green infrastructure include the science of conservation biology and the practice of ecosystem management (Benedict & McMahon, 2002). An analysis of the specific types, extents and qualities of the vegetation, wildlife, topography and resources of an area should be made to determine the role that each landscape feature plays in supporting natural processes (Williamson, 2003). Linking parks and other green spaces for the benefit of communities is also an integral concept. The green infrastructure system can more easily be addressed at an appropriate scale under the megaregion planning approach.
b) Green highway
Green highways may bridge the gap between the transportation networks and environmental systems by bringing the concept of sustainability to transportation infrastructure, and maximizing existing transportation infrastructure. Figure 18 shows the physical characteristics of green highways, including biofiltration, a preserved forest buffer, a porous pavement shoulder, wildlife crossing, stream restoration, wetland restoration, soil amendments, and environmentally friendly concrete. Green highways are built with permeable materials to reduce imperviousness. Since green highways technology uses recycled materials, they can reduce concrete production waste and energy consumption. Using wildlife crossings, such as bridges, culverts, tunnels, and barriers, as a link reduces the risk of vehicular collision. These technologies prevent traditional highway infrastructure from interrupting critical habitats and ecosystems (Green Highways Partnership).
Figure 18. Virtual Green Highway (Green Highways Partnership: www.greenhighways.org)
Building a green highway includes three steps: 'planning and preliminary design', 'final design and construction', and 'operations and maintenance'. Construction of a green highway requires an expansive scope both geographically and functionally because the sphere of influence of natural environments is broad. Also, monitoring and evaluation systems should be managed in broader areas along highway corridors (Green Highways Partnership).
c) Green infrastructure and megaregionsGreen infrastructure is intended to integrate nature back into the community in a way that facilitates various levels of human interaction with the environment based upon the resiliency of the natural resources being protected (Williamson, 2003). An effective network of green infrastructure cannot stop abruptly at the edge of the implementing jurisdiction. There are many laudatory efforts being made to develop and implement informed greenspace strategies, but to date, there is very little coordination between these local initiatives. A megaregion based green infrastructure would be more effective.
2 'Air & Truck' includes "shipments by air or a combination of truck and air" (FHWA, 2006c).
3 'Other Intermodal' includes "shipments typically weighing less than 100 pounds by Parcel, U.S. Postal Service, or Courier, as well as shipments of all sizes by truck-water, water-rail, and other intermodal combinations" (FHWA, 2006c).
4 "Pipeline is included with unknown because region-to-region flows by pipeline are subject to large uncertainty" (FHWA, 2006c).
5 'Rail' includes "Any common carrier or private railroad" (FHWA, 2006c).
6 'Truck' includes private and for-hire truck (FHWA, 2006c).
7 'Truck & Rail' Intermodal includes "shipments by a combination of truck and rail" (FHWA, 2006c).
8 'Water' includes "shallow draft, deep draft, and Great Lakes shipments. Shallow draft includes barges, ships, or ferries operating primarily on rivers and canals; in harbors; the Saint Lawrence Seaway; the Intra-coastal Waterway; the Inside Passage to Alaska; major bays and inlets; or in the ocean close to the shoreline. Deep draft includes barges, ships, or ferries operating primarily in the open ocean" (FHWA, 2006c).
9 Since RPA-defined megaregions, although their identification methods have not been released, , this section uses RPA's delineations as tentative megaregion locations. Recently, Passenger Rail Working Group (PRWG) (2007) and National Surface Transportation Policy and Revenue Study Commission (2007) used RPA's definition.
10 A "Federal-Aid Urbanized Area" is an area with more than 50,000 persons that encompasses the Census-defined urbanized areas (FHWA, 2001).
11 There exist strong flows of Chemicals/Petroleum products via this route (Zhang et al., 2007).
12 Chicago-Detroit/Pontiac corridor is planned to serve at 110 mph within 2 years (Schwieterman & Scheidt, 2007).