Civil Engineering Reference
In-Depth Information
To minimize traf
c delayed by large left-turning volumes at intersections,
provide continuous collector/arterial roadways at 1/2 mile to 1 km spacing or
less
Provide suf
cient residential densities to support bus service
Provide rapid transit service to major activity and employment concentrations
Provide local residential streets with sidewalks that in large urban areas can
afford direct traveler access to bus service
Provide local street patterns that can better accommodate emergency vehicles
24.7.3 Suburban Mega Centers
Mega centers in suburban areas are mainly accessible by private automobiles. These
major concentrations of activities tend to generate heavy peak-period traf
c demand
that can exceed the capacities of the approach and boundary roads and result in
severe traf
c congestion on expressways and arterial roadways that provide access
to the mega centers.
Congestion relief strategies on the roadways serving suburban mega centers
involve proactive actions aimed at (1) increasing the capacities of the access modes
to match the centers
'
traffic demand, or (2) constraining peak hour traffic loads by
limiting the growth of these centers to the capacity of their access roads, and (3)
coordinating the center
s land use development/design to facilitate customer access
by transit or as pedestrians.
Coordinating land use decisions (under local control), land developers
'
decisions
(under private control) and transportation decisions (under State control) is a
challenging task involving competing and diverse objectives (e.g., the
'
financial
interests of private developers, the importance of tax revenues to the local towns
'
operating budgets, and home rule in zoning decisions).
24.7.4 Central Business Districts (CBD) of Large Cities
Mega centers located in centers of large cities (e.g., Manhattan, Chicago, Boston, or
Philadelphia central business districts) consist of high-density commercial and resi-
dential developments where rapid transit access predominates. There is a high volume
of pedestrian trips, and a low per capita share of private vehicle use. Even where most
trips are by public transport, these centers usually face extensive traf
c congestion
where CBD employment exceeds 100,000, and where off-street parking is expensive.
Congestion relief strategies for large city centers typically require a
mix
of
strategies involving operational and physical improvements to increase multimodal
transportation capacity, as well as multimodal travel demand management and
parking management policies.
