Overview of Congestion Relief Strategies - Road Traffic Congestion - page 181

14.4.4.1 Possible Strategies

Relief strategies that focus on removing/reducing bottlenecks produce the most
immediate congestion relief considering that 65 % of congestion delays nationwide
are attributable to bottlenecks 40 % of delay is from recurring bottleneck locations

and 25 % from incident-induced bottlenecks (Table 7.1 and Ref. [ 1 ]).
Strategies that reduce the impacts of nonrecurring congestion delays involve the
ability to detect the event as soon as it happens and to restore the roadway to full
capacity as soon as possible, direct drivers to reduce speed during inclement
weather or when the roadway is being repaired, or inform drivers about the location
and times of special events that are likely to generate surge in traf

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c demand on the

impacted roads.
Strategies that reduce recurring congestion delays at physical bottlenecks
involve grade separation of intersecting traf

c streams; road widening at bottleneck
locations; the addition of merging and turn lanes; and recon guration of entrance

and exit ramps at freeways and expressways. However, to prevent new traf c

attracted to the improved roadway from nullifying the travel time bene ts of bot-

tleneck removal, strategies that reduce bottleneck congestion in highly congested
roads should be coupled with strategies that control traf

c demand on these roads

(e.g., ramp metering).
In urban areas under 1 - 1.5 million people, recurring congestion can be reduced
in intensity, extent, and duration. In larger urban areas, however, congestion relief is
generally manifested in reducing its duration .
Strategies involving the removal of operational bottlenecks are relatively easy to
implement from an operational standpoint when they are the responsibility of one
transportation agency. However, where the owners of the transportation infra-
structure are agencies typically controlled by different units of government, coor-
dination of congestion management strategies among these units may be time
consuming and not always easily achievable especially when the limited funding

available for this purpose may not be transferrable between agencies.

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14.5 Summary

Most urban areas experience more congestion, poorer pavement and bridge condi-
tions, and less public transportation services than required. A variety of solutions is
needed for different metropolitan areas, their cities, job centers and shopping areas,
and neighborhoods [ 1 ] Some of these will involve constructing new road capacity,
others will require improving the throughput of existing roads, adding travel alter-
natives to the automobile, the development of diversi ed land use patterns, or the

redevelopment of neighborhoods that encourage use of non-motorized transportation.