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indicated that the rate of growth of passenger
miles traveled within the county exceeded population growth.
The city anticipated that the increase of traffic at the I-10/Estrella
intersection would coincide with the opening of the new Super Wal-Mart
there in the early summer of 2005. Wal-Mart was funding the
signalization, and installation was set for the spring of 2005.
Earlier problem
Traffic volume became unmanageable as an
uncontrolled intersection by early 2004. There were enough collisions
that Goodyear placed stop signs at the base of the I-10 off-ramps to
control the traffic merging into the Parkway. This caused traffic to
back up the ramp and out into the westbound lanes of I-10 at rush hour.
The delay was unacceptable, and collisions continued to occur. Finally,
the city carved left-turn lanes out of the parkway median and put an
additional stop sign on the Parkway itself. Collisions were reduced, but
traffic delays continued to mount. The motoring public was quite
dissatisfied.
The city knew that traffic signals would
alleviate the problem and attempted to accelerate their installation,
but ran into a supply problem. Goodyear uses a distinctive style of
traffic pole, available from a single source. That source was under a
heavy workload, and could not supply the poles at a time earlier than
initially scheduled.
Temporary signals
At this point, Dave Mueller at Goodyear Traffic
Operations and Don French, then Public Works Director (since retired),
got creative. He asked
OMJC Signal, Incorporated if they could temporarily signalize the
intersection until the permanent signals were installed. OMJC
manufactures a portable signal mast arm, called the Pop-Up, with
solar-powered, radio-connected signals and controls.
While each of these features is available from
more than one company, what swung Dave’s favor to OMJC is their unique
use of an industry standard NEMA TS1 controller and conflict monitor to
run a complete intersection. These NEMA components are very similar to
what Mueller already had in most of his traffic control cabinets in the
city, and have a very defensible record in terms of tort liability.
Familiarity with the technical standard and good tort defense are often
key issues with governmental entities concerned with traffic control.
Scott Nodes, the traffic engineer for the city,
determined that the intersection would require six trailers. OMJC agreed
to take on the job, even though no one had ever before tried to run six
trailers interconnected by radio and under the control of a single NEMA
controller and conflict monitor.
To further complicate matters, OMJC’s production
capacity was nearly fully committed at the time. In short, there was no
possibility of OMJC producing enough trailers within the allotted time.
OMJC creatively found a means of retrofitting
their secondary trailer controls onto a trailer model manufactured by a
competitor, which allowed the Master Pop-Up to control that trailer.
Partnering with United Rentals, which already owned some of the
competition’s trailers, OMJC was able to use United Rentals’ trailers to
meet the need in time.
Scott Nodes determined the trailer placement,
and worked with the Arizona Department of Transportation to determine
barricade requirements and placement. Trailer placement required two
trailers to be put in a median or a turn lane. The narrow width (6 feet)
of the Pop-Up was a great benefit.
On these two Pop-Ups, the signals needed to be
reversed from standard, which was readily accomplished. Since the Pop-Up
has the longest arm in the industry, this placement used the extra
length to an advantage and placed the overhead signals in a position
that was clearly visible to both through traffic lanes in each
direction. Because the trailers are all solar powered and
self-contained, they could be easily relocated to accommodate the
contractors installing the permanent signals in the spring.
The six trailers were easily placed and
initialized. However, because this installation broke new technological
ground, there were early problems with reliability. Here’s where the
NEMA conflict monitor and fail-safe mode, as well as the on-board cell
phone auto-dialer (which calls in case of failure), proved their worth.
OMJC and city engineers stuck by each other, and, ably assisted by Jerry
Borneman at the United Rentals Phoenix store, achieved a reliable and
safe system that was in operation for six months.
The final result?
Traffic moved. Collisions were eliminated. The
motoring public was better served, and letters to the editor of the
local newspaper moved on to other topics. The work zone was safer for
the contractors installing the permanent signals. |
