Transportation -
Intelligent Transportation Systems (ITS)
Mesa's ITS Group is responsible for the
construction, maintenance, and operation of traffic
signals and related ITS (intelligent transportation
systems) technology. Nearly all of Mesa's signals are
interconnected and operate as a system to reduce overall
delays throughout the City. Mesa's skilled field
technicians and staff in the City's state-of-the-art
Transportation Management Center (TMC) work together to
keep traffic moving.
Vehicles starting out straight (e.g. not making a turn from a side street) at
a major intersection at the beginning of a green will experience less stops and
delays.The signal timing is adjusted at various times of the day to accommodate the
changing traffic patterns. However, there are times when the amount of traffic
exceeds the capacity of the roadway. When this happens, backups and delays are
inevitable. Carefully planned signal timing helps use the available street
capacity to its utmost.
Approximately two-thirds of Mesa's traffic signals are equipped with
preemption. Fire department vehicles have special coded transmitters that
trigger the system. This equipment makes the traffic signal give the green
indication to the approaching fire vehicle to help emergency services personnel
arrive quickly and safely to where they're needed. You may have noticed the
detectors for the system. In Mesa they are typically mounted to the top of the
signal head, at the end of the mast arm, over the roadway.
The most common method uses a coil of wire embedded in the road surface. An
electronic signal running through the wire of this inductive loop is affected by
the presence of vehicles. An interface device in the traffic signal cabinet
tells the traffic signal controller when a vehicle is present based on these
inductance changes. The principle is essentially the same as how a metal
detector used to find coins on the beach works.If the loop of wire in the street becomes damaged, the traffic signal controller
will interpret this as if there were always a car present. This means, for
example, that a left turn arrow or side-street indication would be displayed for
its maximum time with no vehicles present.
Many recently constructed or renovated intersections have video detection
devices which monitor the lane usage through video input. Detection zones are
drawn on an image of the roadway. A computer program running inside the
detection device determines when vehicles enter a zone and pass that information
on to the traffic signal controller. There are several advantages to video-based
detection such as not being damaged by road work, being re-programmable for
situations such as construction where lanes may be moved, and the ability to
send images back to the TMC where City staff can see traffic incidents or
congestion and make timing adjustments.
Pedestrian indications consist of a walking person symbol (i.e. "walk" indication) and an upraised hand
(i.e. "don't walk" indication). The walking person symbol means
you can begin crossing
now. This indication is typically on for a short amount of time just to get you
started. The flashing hand means if you've started crossing, finish crossing.
The flashing hand also is a warning that if you haven't started crossing yet,
don't start because it is too late to safely cross before the signal changes.
If the hand (i.e. "don't walk" indication) is on solid you shouldn't be in the
street.
When crossing the street, if
there is a button present for the direction you are traveling, please press
it. When the button is pressed the controller knows to bring up the pedestrian
indications to allow enough time for you to cross. Without the button press,
the traffic signal may only give enough time for vehicles. Pressing the button
doesn't make the signal turn green any faster but it does give more time for
pedestrians to cross the street. If there isn't a button, don't worry, the
signal will display the pedestrian indications automatically.
Pedestrian Crosswalks - How Safe Are They?
Pedestrian Safety Tips
The City of Mesa's
Transportation Management Center (TMC) is bringing it all together. This
facility is the nerve center of Mesa's Intelligent Transportation Systems (ITS)
efforts. This facility houses systems which can notify City staff of any
unusual incidents. Based on this information, traffic signals near the scene
can be adjusted to better accommodate the change in conditions. Several key
intersections are monitored from the TMC, and City staff is working diligently
to expand this technology throughout Mesa. The coordination of these
efforts all results in less traffic congestion and delays. This advanced
technology also allows TMC staff to work with neighboring cities on monitoring
traffic conditions and accidents, making your commute an easier one. The TMC is
truly one of the most advanced facilities of its
kind in the nation, and the City is pleased to put
this state-of-the-art technology to use for the
benefit of all who travel in Mesa.
Mesa has switched to LED (light emitting diode) traffic signal indications instead of incandescent lamps. LEDs
use a fraction of the energy when compared to the older technology and they have
a life-expectancy of eight to ten years compared to one to two. Several years ago Mesa
started building all new intersections with LED indications and then shortly
thereafter a retrofit program began. The switch to this more efficient
technology means that, even with an increase in the number of traffic signals,
the electric bill has dropped by over $260,000 per year! |
