Signal Synchronization
Why can’t the signals in Spokane be
synchronized so I can drive down an arterial without stopping? Doesn’t this waste
gas and pollute the air?
The traffic signals in
Spokane are managed by an advanced central computer system that communicates
with almost all signals in real time. The purpose of the system is twofold; one
is for maintenance and monitoring, and the other is to implement and control
synchronizing traffic patterns.
The City operates 251
signals, of which 180 will be in a synchronization plan during some part of the
day. So, there are 71 intersections that are not ever timed with respect to
‘adjacent’ intersections. As might be expected, the tightly spaced
intersections in the downtown are synchronized 24 hours per day, while the more
far spread intersections will not be synchronized at all. Some groups of
intersections may be operated in a plan during the heaviest, or most
directional traffic volumes. For example, some intersections on Nevada Street
are only synchronized during the morning or afternoon peak traffic flows.
During the non-synchronization times, the theory is that cross street traffic
would be un-duly held up while the signal provided time (now unused) for the
now non-existent traffic on the primary corridor.
The primary traffic flows in
Spokane have historically proven to be heavy inbound (towards the downtown or
freeway) in the morning, and heavy outbound (away from the downtown or freeway)
in the evening. Naturally, signal timing is set to reflect those conditions. If
you are driving in directions different than the primary flow, you will
probably see poorer system performance.
During the non-peak hours,
the system tries to optimize to favor more localized demands. These patterns,
for example, may favor shorter travel links within larger corridors, or heavier
left turning and crossing traffic that may be shopping.
The City regularly responds
to service calls that may reveal problems with traffic flow. In some cases,
problems can be resolved by dispatching crews that may find and repair some
failed local component. In other cases, extensive analysis of local conditions
may dictate changes in actual timing values or even signal design. Such changes
occur on a consistent basis as conditions change or simple errors are revealed.
Federal and traffic industry
(Institute of Traffic Engineers) guidelines and complex software programs are
used to determine the best pattern of operation for any given traffic flow.
Some software tools measure the effectiveness in terms of gallons of gas
consumed and in pounds of pollution produced. The Environmental Protection
Agency monitors Spokane air quality, and participates in system implementation
and design.
The single
greatest element of smooth, uninhibited traffic flow is grid geometry. In a
perfectly spaced street grid with equal distances between intersections, flow
management is fairly straightforward for traffic in all directions. As the
street system departs from perfection, flow performance quickly deteriorates,
as compromises have to be made to favor the heavier volumes.
If you have any questions about Traffic
Signals, please contact the City of Spokane, Traffic Operations Division at
(509) 232-8800.
This site
will be updated as further information is developed and formatted for online
access.
|
The information contained on these pages is compiled from various
sources and is subject to constant revision.
This material should be used for informational purposes only. Please refer to the Citizens Reference Guide or contact the street department directly for further
information. |
Please
send any questions or concerns for the street department to:
Spokane
Streets
To contact the Street Department, call (509) 232-8800 during normal working
hours.
If you are in need of after hour assistance please contact us at (509)
625-7733.
or send correspondence to:
City of Spokane Street Department
901 N Nelson St.
Spokane WA 99202-3769
Any Questions
or Suggestions on this web page please email us at: info@spokanestreets.org