east liberty station: realizing the potential - City of Pittsburgh

Long-term: Roundabout at Penn
Avenue and Shady Avenue
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Modern roundabouts in both the United
States and other countries have achieved
a 50 to 90 percent reduction in collisions
compared with intersections using traffic
signals. Studies have found a particularly
significant reduction (up to 90%) in
the number of crashes that result in
death or disability, in good part because
roundabouts eliminate the high-speed,
severe angle crashes (such as T-bone and
head-on crashes) which occur at traffic
signals. In addition, the high capacity of
the roundabouts is what makes it possible
to remove lanes between intersections.
This can potentially allow for the addition
of bicycle lanes in lieu of the underutilized
travel lanes.
Properly designed roundabouts provide
large safety benefits for pedestrians, when
compared to intersections controlled by
either stop signs or traffic signals. For
example, a Dutch study of 181 intersections
that were converted to roundabouts found
an 89 percent reduction in casualties
(fatalities and injuries). Other studies
have also found major improvements in
pedestrian safety. This reduction in crashes
occurs because roundabouts provide three
key features that pedestrians need for a
safe crossing: simple decision-making, short
crossing distances, and low traffic speeds.
Decision-making is simple because
pedestrians cross one direction of traffic
at a time, traveling from curb to splitter
island, then from splitter island to curb.
Vehicle speeds are kept low by the physical
constraints of the roundabout. On one
side, pedestrians cross behind drivers who
are waiting to enter the roundabout. On
the other, drivers exiting the roundabout
at low speed have room to pause outside
the circle, while pedestrians cross the
13 feet from splitter-island to curb. By
contrast, crossing Penn Avenue at a signal,
pedestrians face conflicts from both rightturning
and left-turning drivers who also
have a green light, and also are at risk from
drivers making a right-turn on red. All of
these drivers at signals are simultaneously
searching for gaps in traffic. Because
roundabouts reduce the large number
of conflicts found at signals, they are
able to provide safety improvements for
pedestrians.
Roundabouts also slow traffic, and
are particularly useful in areas where
drivers should recognize the presence of
pedestrians. They can also serve as an
attractive gateway to a community. As
East Liberty develops land adjacent to the
busway station, a more visible transit node
will emerge which can be greatly enhanced
by gateway treatments in the center of the
roundabout.
Based on forecasted traffic volumes
developed for the Eastside Development
project, a roundabout that could work
at the Penn Avenue/Shady Avenue
intersection is shown in the above diagram.
A conceptual illustration of this roundabout
superimposed onto the station area
plan is shown at right. This roundabout
would need to be approximately 180 feet