Assessing and Managing the Ecological Impacts of Paved Roads (2005) / Chapter Skim
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2 History and Status of the U.S. Road System
2 History and Status of the U.S. Road System
Pages 37-61
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From page 37... ...
The current system of paved roads handles a volume of traffic on the order of 2.9 × 1012 vehicle miles per year,1 or about 8 billion vehicle miles per day (DOT 2003)
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From page 38... ...
In addition, ecological impacts, environmental mitigation, and simple scale of the road surface area vary widely by road type. For example, depending on the scale of concern, an eight-lane interstate highway connecting major cities would have much greater fragmenting effects than a two-lane rural road.
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From page 39... ...
In 1806, the federal government began its most ambitious project to date: construction of the National Road, also known as the Cumberland Road, from the Potomac River at Cumberland, Maryland, inland to the Ohio River at Wheeling, West Virginia. By 1831, revenue began drying up, completed sections of the Cumberland Road were turned over to the states, and the federal government halted all road funding.
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From page 40... ...
. Interstate Highway System A few intercity highways, such as the Merritt Parkway in Connecticut, and the New Jersey and Pennsylvania turnpikes were built in the 1930s through the 1950s, and a few major cities had some limitedaccess, divided, multilane highways.
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From page 41... ...
of paved public roads in the United States are two-lane rural highways, and the remainder are urban and rural multilane roads. The road network is expanding slowly, having only 55,000 lane miles built between 1987 and 1997 (less than 0.2% increase per year)
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From page 42... ...
During the 1990s, the largest increase (41.9%) in road use occurred on the principal arterial urban roads (not urban interstates)
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From page 43... ...
0012 Functional alrie ro ro A 2-1 ectl E onali nct etatsre aysw art alrie ways/ palcin art nori ectllocrjoa FHW col or nori TABL Fu System Int Free express Pri M M M ectlloC la ce:r Local Tot Sou
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From page 44... ...
One major grouping is the NHS, which comprises the interstate highways and a large number of the high-volume arterial roads. Although not exclusive, most of the considerations of ecological impacts that occur in subsequent chapters consider the impacts from the first three functional types listed above.
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From page 45... ...
The interstate system accounts for only 1.2% of the nation's total miles of roadway (Table 2-2) , yet interstate highways convey 24% of the annual VMT in the United States and 41% of total truck VMT, suggesting their importance to commercial transportation.
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From page 46... ...
The NHS serves major population centers, intermodal transportation facilities, international border crossings, and major travel destinations. It includes the interstate systems, other rural and urban principal arterials, highways that provide access to major intermodal transportation facilities, strategic highway network connectors, and the defense strategic highway network (Figure 2-2)
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From page 47... ...
Source: FHWA 2001b. TABLE 2-3 National Highway System Mileage and Travel in Rural and Urban Areas Rural Urban Total NHS Mileage Interstate 33,150 13,527 46,667 Other NHS 85,882 28,629 114,511 Total NHS 119,032 42,156 161,188 NHS Percent of Total Mileage Interstate 0.8 0.3 1.2 Other NHS 2.2 0.7 2.9 Total NHS 3.0 1.1 4.1 NHS Travel (millions VMT/yr)
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From page 48... ...
Travel represents vehicle miles traveled per year. Source: FHWA 2001.
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From page 49... ...
Local roads and streets primarily provide access to adjacent land and are generally not maintained by a state highway agency. Local functional systems serve only 13.2% of total VMT, but these roads account for 68.8% of the nation's total roadway miles (Figure 2-4)
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From page 50... ...
This system of roads comprises circular roads (hubs, belts, and ring roads) that go around a city center at various distances and separate roads (spokes)
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From page 51... ...
These include concrete barriers, guardrails, noise barriers, bridges, culverts and pipes, and overpasses and underpasses. Each of these structures has a particular ecological effect.
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From page 52... ...
Some Jersey barriers are used for traffic separation on freeways and interstate highways, and many others are used only temporarily. Temporary units are used mainly to enhance safety in construction work zones.
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From page 53... ...
Three-dimensional models of the alternatives are sometimes used to obtain informed public input into the decision. Noise Barriers Noise barriers are designed and built primarily to muffle highway traffic noise in residential areas, schools, playgrounds, and other sensitive
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From page 54... ...
road system. It reported that most of the existing road surfaces in the system are in good condition but that an aging set of bridges and other engineering structures are a challenge to the system.
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From page 55... ...
These issues are discussed in the following sections. Travel Congestion on Principal Arterial Roads in Urban Areas The use of urban roads continues to outpace the use of rural ones.
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From page 56... ...
Many sources suggest that travel is becoming more congested. The percentage of travel under congested conditions (percentage of daily traffic on freeways and principal arterial streets in urban areas)
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From page 57... ...
History and Status of the U.S. Road System 57 FIGURE 2-7 Traffic congestion map showing a concentration of congested highways in the southeastern and south-central regions of New Hampshire.
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From page 58... ...
Structurally, porous pavement has not proved to be as durable to heavy trucks and high traffic volumes as other road surfaces because of movement of water under the road, resulting in cracking. Porous pavement also is a problem in states having to deal with snow removal because the sand and salts used in snow removal clog the openings.
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From page 59... ...
In 2000, 29% of the nation's estimated 590,000 bridges were considered structurally deficient or functionally obsolete (Table 2-6)
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From page 60... ...
The network comprises different functional types of roads (interstate, arterial, connector, and access) as well as rural or urban areas where roads traverse.
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From page 61... ...
Since the 1960s, urban road travel has become greater than rural road travel; yet the later has more than doubled, and that has important ecological impacts, as discussed in Chapter 3. Indicators of congestion in urban areas are increasing.
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