Civil Engineering Reference
In-Depth Information
Table 17.3
Some examples of intersection grade separation
Location
Type
Flyover
or
Left
turn
fl
3-level
diamond
Interchange
y-
under
fl
yover
Boston
Cambridge Massachusetts Ave at
Commonwealth, Huntington,
Memorial Drive
⃝
Chicago
Western at Belmont and Clybourn
⃝
Archer at Ashland
⃝
Detroit
metro area
Telegraph Rd (US 24)
and 8-mile road
⃝
Miami
Beach
⃝
New York New Jersey
Route 4
-
17
⃝
First Ave at UN
⃝
Grand Concourse at Fordham Rd
⃝
Seattle
Aurora
⃝
Washington Massachusetts Ave
⃝
Connecticut Ave, Dupont Circle
⃝
40 ft of
width to a roadway. Ideally the number of lanes should be the same as those on the
parallel roadway to avoid bottlenecks the start and end points.
The
fl
fly-overs and underpasses on roadways normally add about 30
-
17.2.3 Street Connectivity, Continuity, and Spacing
Street patterns in cities and suburbs re
ect topography, settlement densities, and
policies regarding street spacing and subdivision requirements. City street grids are
usually closely spaced, while many suburban streets are circuitous, discontinuous,
and usually spaced far apart.
Systems of streets with circuitous and discontinuous routing patterns increase
trip lengths and discourage walking trips and bus transit use.
Compared to cul-de sac neighborhoods, traditional neighborhoods built on grid
systems combined with higher development (mixed use) densities experience a
lower VMT per capita and higher utilization rates of non-motorized modes [
13
]. On
traditional grid networks, local streets provide an alternative to arterials for short
trips and lessen the traf
fl
c demand on arterials (e.g., see Fig.
11.2
).
