172Built systems, built areas, and whole regions
[S6]Cities without ring roads have few primary radial roads, and paved two-lane radial
roads areessentially limited to cities without ring roads(Figures7. 2and7. 3).With few widelyseparated radial highways, perhaps less pressure builds for
aring road. Two-lane radials may suggest mainly local traffic rather than long-
distance intercity transport travel. Housing and jobs are local rather than dis-
persed, so commuter traffic and associated commuter residential areas are lim-
ited. The adage, ‘‘If you want to work in a city, move and live there,” seems to
apply. Erzurum, the one exception to the pattern, has two-lane radials with a
partial multilane ring road (Color Figure17).[S7]Cities with considerable ring-road length normally have relatively few primary radial
roads,and cities with many radials have little ring-road length(Figures7. 2and7. 3).In general, cities seem to either invest in many primary radial roads that may
protect more nearby greenspace or invest in a ring road. More radials mean more
strip development, more interrupted stream/river corridors, more barriers to
wildlife movement, more connected greenspace, and more in-and-out greenspace
access between city and countryside. More radial roads also imply more human
dependence on the metro area, rather than dispersed movements in surrounding
landscape areas.
Beijing is an interesting exception, with both a relatively complete ring road
and many radials (Color Figure7).Beijing has heavily invested in ring roads, with
thefourth ring relatively complete and the seventh ring beginning in places
(Yang Rui and Laurie Olin, personal communications). No large greenspace is
apt to remain for future residents or for nature near the metropolitan area.[S8]Cities with more radial roads may also have more radial commuter-rail lines extending
beyond the metropolitan area(Figure7. 4).Although limited data on commuter-rail systems were collected, apparently
commuter-rail service is mostly within metropolitan areas. Radial commuter-
rail lines, however, serve separate communities outside certain metro areas.
Cities with many radial highways plus outside commuter-rail lines (London,
Philadelphia) may have a large outside commuter population that demands an
alternative to radial vehicular-traffic flows. Large connected nearby greenspaces
could be maintained with such an emphasis on radial transportation routes.Airports and aircraft noise
[S9]Most urban regions have one or two major airports, while 10 % have five or
more airports(Figure7. 5).