Adaptation Strategies for Managing Recurring Congestion—Operational Improvements - Road Traffic Congestion - page 210

entering and leaving a development site reduces con fl icts and simpli es signal

operation.
In this example, the left turn movements entering and exiting take place
essentially at the same time. This two-phase operation results in shorter

“ red ” times

and less delay for motorists on both the arterial and site-access roads.

16.7 One Way Streets

One-way streets have improved traf c speed and reduced congestion since ancient

times. They were found in Pompeii where the narrow lanes allowed for the passage
of only one lane of vehicles [ 3 ].
In the US, one-way streets

first emerged on Chestnut Street in Philadelphia and
in the Park Row section of Manhattan in 1907. They were progressively imple-
mented in American cities since the 1920s. By 1939, 85 % of the streets in Man-
hattan operated one-way. Most urban areas in the United States and Canada have
one-way streets.

16.7.1 User Benets

One-way streets are a low-cost strategy that reduces delay, increases traf c speeds,

and improves safety. The delay reductions translate into lower emissions and better
air quality. One-way street operations increase road capacity and reduce intersection
con

icts, travel times and crashes. Case studies from the 1950s indicate that one
way conversion from two-way traf

fl

c fl flow increased traf c speeds from 20 to 50 %,

with a corresponding reduction in crashes [ 18 , 19 ].
The changes in traf c volumes, trip times, and number of stops resulting from

converting Fifth Avenue in Manhattan to one-way operation are as shown in
Table 16.6 .
The Madison Avenue-Fifth Avenue one-way couplet in Midtown Manhattan
reduced accidents by 27 % and personal injuries 28 % [ 11 ].

Table 16.6 Traf c volume
and performance changes
resulting from two way to one
way operation on fifth avenue,
Manhattan

Item % Change

Average daily traf c volume +19

Average trip time 31

−

60
Source Reference [ 20 ] © National Academy of Sciences,
Washington, DC, 2000. Reproduced with permission of the
Transportation Research Board

Average number of stops

−