Transportation modes 233hydrology, wetlands and streams, block animal movement across the
landscape, subdivide natural populations into smaller populations,
road-kill animals, and disperse air pollutants into the environment
(Figure9.1).
(B) Degradation zones by highway.Increasedvehicular traffic on highways cre-
ates wider adjacent zones of degraded animal communities (presum-
ably due to traffic noise), wider highways generally (often with more
traffic) are greater sources of non-native species, eroded earth material,
stormwater contaminants, and atmospheric pollutants.
(C) Highway protection of the matrix.Amore concentrated, safe, and efficient
transportation system to access resources, homes, and other human land
uses is valuable for reducing dispersed human impacts on nature and
natural systems across the landscape.
(D) Highway network.Busier and wider highway corridors increasingly reduce
landscape connectivity and subdivide an urban region into sections,
with a mesh size normally suitable for relatively separate small popula-
tions of large animals.
(E) Perforated highway corridor.Increasingly perforating a transportation cor-
ridor with passages, from tiny wildlife tunnels to culverts, underpasses,
and overpasses, reduces habitat fragmentation by providing for rela-
tively natural movements and flows of wildlife and water.
(F) Closing roads.Progressively closing spur roads and low-usage roads in and
bymedium-to-large natural patches is an especially effective way to cre-
ate large natural patches and their many important benefits for nature
and society.
(G) Adding radial-route capacity.Adding transportation capacity on a city’s
radial route stimulates growth and development in that direction.
(H) Adding a ring road.Adding an outer ring road provides flexibility in
movement for suburban (peri-urban) residents and catalyzes growth and
development over a broad outward zone.
(I) Trucking center.Atruck (lorry) transportation terminal near the metro-
area border facilitates the transfer of manufactured goods and agricul-
tural products for long-distance trucks, as well as small-truck movement
serving local farms, industries, markets and restaurants, in effect provi-
ding economic efficiency and better traffic flows on congested urban
streets.
Communities and development
(A) Commuter rail lines.Light or heavy rail lines and streetcars/trollies that
extend outward, offering convenient service beyond the metro area,