The holy grail of efficiency and
reduced driving stress is never (or at least seldom) stopping for a traffic
signal. To a degree it's predicting the future, and that will always yield
mixed results. It's not as hard as it would seem, but as with any driving
advice, your mileage may vary. This is ground-rules for how to 'model' your
local lights. It will be different for virtually every intersection, city/town,
state/province, and country.
Essay Writing:
Keep your readers engaged in your essay writing
Keep your
reader traveling in the right direction
by using
clever "traffic signals" in your
essay
writing.
If you're writing an essay, you want to get a good grade, or
at least to make your reader understand what you are trying to say. When essay
writing, try to think about your paper from your reader's point of view.
Imagine your reader as a tourist, setting out on a journey, traveling down your
written page.
Give the reader direction in your term paper
From the
outset, he or she will want a roadmap. What lies ahead? In the first paragraph
of your essay, you'll need to give Dear Reader a summary look at where she is
going. That's the only way she's going to feel safe and secure about making her
way through the verbal landscape of your term paper. Just a few sentences or a thesis statement will do; consider the following
example:
"The
aardvark and its sleeping habits, its diet, and its play will be discussed,
with examples from species found on the African continent."
Keep your reader on track with traffic signals
Once your
essay's road map is set, the reader is going to expect traffic signals along
the way. Capital letters mean a green light; periods or full stops mean a red light. Without them,
Dear Reader will speed along, crashing into your term paper's carefully
constructed sentences. If you string together a few sentences without signals
to indicate stop and go, expect to encounter a traffic jam or two along the way
in your essay writing.
Gently steer your reader through transitions in your
term paper
Another
signal you need to consider in your essay writing is to give your reader
adequate notice before the road branches off to somewhere else. In other words,
when you're starting a new paragraph in your essay, give your reader some
warning. Dear Reader doesn't like abrupt surprises. We liken this to one
of those road signs with an arrow pointing backward and another one pointing
ahead. A sentence like, "Not only does the aardvark sleep upside down
(that's the sign pointing backwards to the discussion you've just had about its
sleeping habits), but it prefers to eat its meals in this position too (that's
the road sign pointing to the discussion ahead)." If you put one of these clever
two-way road signs at the beginning of a new paragraph in your term paper, your
reader will purr right through the transition, secure in where she's been and
where she is about to go.
State the obvious
It always
helps to point out the obvious to the reader/traveler, just like those road
signs that say "twenty kilometers" to your destination, and then a
few minutes later, "ten kilometers" to your destination. Wherever you
can in your essay, enumerate things and organize neat categories—your reader
will appreciate it. If we continue with our aardvark example, we would include
sentences like: "There are three things aardvarks like to eat: bugs,
roots, and leaves. Bugs are found in the.... Roots are plentiful..." and
so on. This information will help the reader keep all of the mileage signs
clearly in view.
End your essay with a quick synopsis
Finally, if
Dear Reader makes it through your prose, she'll want to stop at the end of the
trip and savor where she's been. That's the time to give a synopsis, a look back over the road, and
maybe a suggestion for a new travel direction. We would thus conclude our essay
on aardvarks by saying: "It is clear that the aardvark has peculiar
sleeping habits, subsists on a diet of bugs, roots, and leaves, and likes to
play hide and seek with others of its species. What is not known, and may merit
further research, is why the aardvark spells its name with two As."
Does your
essay lead readers astray? Then submit it to one of our essay editing services today and let a trained
professional help you get it back on track.
· Know
approximately what your 'net' rate of travel will be, and consider that instead
of the speed limit, or how quickly you can move from light to light. A
45 mph (72 km/h) speed limit is often a net speed of 30 mph
(48 km/h), sometimes a lot less, in an area with traffic signals. The fact
that you're moving along at 30 mph (48 km/h) in a 45 mph
(72 km/h) zone should make no difference to your travel time, especially
if you are almost never stopping.
Ad
· 
2
Know where
signals are 'coordinated'. On sections of road where this is true, once you are moving with the
flow of traffic, maintaining a given speed will usually get you through
without stopping.
· 
3
Learn that
green is bad, and red is good. This is the opposite of what most people think, but
absolutely works. A green light can be totally unpredictable. It might stay
green right up until you're almost committed and then turn yellow. Green will
betray you. A green light will tempt you to speed toward it and force you to
slam on your brakes. When you are approaching a signal that is red, you are
covering ground instead of idling at the signal. Well coordinated signals will
typically be red as you approach then turn green shortly before or after you
arrive at the intersection.
· 
4
Discover
that red lights are the most forgiving and the most beneficial things to see a
ways up ahead. You know
you'll stop at a red light, which makes it predictable, but it might just turn
green, so if you slow down enough approaching it, you might never stop. At the
very least, you won't have worn brakes and burned fuel keeping the car moving
fast. Now it's only a matter of trying to work out how long it will remain red,
and how long it will be green after that, and moderate your speed to be moving
at the right rate when you reach the intersection to follow the other cars
through without stopping at all (though not so fast that you can't stop if they
stall, the signal doesn't behave like you wanted it to, or whatever other
unpredictable things happen). You may also be able to tell from where you are
that even though the light will turn green about when you get there behind the
traffic, that you won't be making it through, and plan accordingly.
· 
5
Get a 'feel'
for where/when to start watching and predicting where your car should be when
considering a traffic signal. This takes 'fuzzy' experience, because it's different
for most intersections and is different for different cars.
· 
6
Watch not
only at the current light, but the next one and occasionally even the one after
(if not too dangerous to do so, like when you're stopped and have nothing
better to do), where signals are spaced closely together. You can often tell fairly precisely
what the next light will do after the current one changes.
· 
7
Watch the
pedestrian crossing signals. If it's green or only just started flashing red, your
green light is still 'fresh', and you might make it.
· 
8
Watch the
intersection for cars waiting on the crossroad, or in a left-turn lane facing
you. If you see
these things, your green light will in all probability betray you.
· 
9
Watch left
turn signals for traffic traveling in your direction. If you have a green light, and the
turn signal facing you just turned green, and there are still cars turning,
your green light may be 'fresh' enough to make.
· 
10
When
attempting to make a left turn yourself, if there is other traffic waiting in
the turn lane for a left turn light, you can occasionally time your arrival
such that the left turn light has turned green, and traffic is moving. More often than not, you can't.
· 
11
Left turn
signals can lead or lag the straight through green, especially along
coordinated routes. Each signal
will likely be phased for a particular day and time, so pay attention to learn
what each signal does on your commute.
· 
12
Make
opportunistic plans for entering parking lots. Many parking lots have multiple
entrances on different sides. With a lot on the left, if your traffic light has
turned red, or is going to turn red, consider taking the a left turn instead of
proceeding to a later entrance. If it's fresh and green, maybe proceed ahead to
an uncontrolled left turn lane (depending on traffic) to avoid waiting for the
signal to cycle all the way through to a left turn. Similar when approaching a
lot on the right, especially if you are in a 'right on red' jurisdiction. Mind
the pedestrians, though.
· 
13
Make opportunistic
plans for your route. Most
American cities are laid out like a grid. There are multiple paths/doglegs to
take to reach the same destination, on or off freeways. Often some of these
paths have fewer signals, or more 'friendly' signals. Balance this with the
knowledge that every turn is usually a stop. At certain times of the day or
week, an otherwise 'impassible' industrial zone with relatively few signals can
be absolutely deserted.
Traffic Signals Information
The first
traffic signal in Queensland was switched on, 21 January 1936. It was located at
the intersection of Ann, Upper Albert and Roma Streets.
Queensland
now has around 1,700 signalised intersections under the central control of a
fully integrated Intelligent Transport System (ITS) known as STREAMS.
The
Department of Transport and Main Roads uses STREAMS to:
- coordinate traffic signals;
- record faults (eg. blown traffic signal lamps);
- record data for performance monitoring (eg. traffic volumes at intersections);
- manage traffic incidents and special events;
- provide traveller information; and
- provide parking guidance.
- Why have Traffic Signals
- How do Traffic Signals Work
- Modes of Operation
- Pedestrian Crossings at Traffic Signals
- Roundabouts vs Traffic Signals
- Reporting Problems / Concerns
- Traffic Signal Coordination
The main
reason for traffic signals are:
- to allow road users to safely navigate through an intersection;
- to give priority to a particular direction / mode of travel at different times of the day; and
- through coordination, allow large volumes of traffic to pass through the network with minimal delay.
A standard
set of traffic signals consists of:
- a traffic signal controller;
- vehicle detector loops and pedestrian push buttons;
- traffic signal lanterns; and
- posts, pits and underground electrical cables that connect all the components together.
The traffic signal controller
Housed in a
grey metal box on a corner of the intersection, the controller is the 'brain'
of the system. It is a computer that processes information received from the
detector loops and pedestrian push buttons and changes the signal
lanterns in accordance with its programming. Based upon the prevailing
demands, the controller determines the length of the green signal for each
traffic movement and controls the transition from one combination of green and
red signals (known as phase) to the next. It can operate in a 'stand alone'
manner or be programmed to coordinate with a series of adjacent traffic
signals.
Vehicle loop detectors and pedestrian push buttons
Vehicle loop
detectors and pedestrian push buttons are the 'eyes' of the system. They are
mechanisms motorists and pedestrians use to make the controllers 'see'
them and change the signal to give them right of way.
Vehicle loop
detectors are loops of wire buried in the road leading up to the stop line at
the intersection. When a vehicle is passing over the loop the
magnetic field (inductance) of the loop changes. The controller detects that a
vehicle is waiting to proceed through the intersection.
Likewise,
when the pedestrian push button is pressed the controller knows that a pedestrian
is waiting to cross.
Traffic signal lanterns
Traffic
signal lanterns are the means by which the controller directs traffic. They
tell the road users when to go and when to stop. Queensland traffic signal
lanterns follow universal traffic signal colour conventions. GREEN = Go if it is safe to do so; YELLOW = Stop if it is safe to do so; and RED = Stop.
Modern
pedestrian signals use the symbolic walking
green and standing red figures
figures although there are still older lanterns around that display WALK and DON"T
WALK.
Over time,
the department is converting standard signal lanterns to LED (Light Emitting
Diode) lanterns which are very energy efficient and long lasting.
Signal phases and cycles
Each
combination of green and red signals that the controller is programmed to
display is called a phase. Each phase has a programmed minimum time so that
once the signals have entered a phase they cannot change again until the
minimum time has expired. One complete sequence of all the vehicle and
pedestrian movements (phases) at an intersection is known as the signal cycle.
In Queensland, the duration of a cycle is usually between 50-150 seconds. The
cycle time varies by location and time of day.
The yellow signal
Traffic
signals change from green to yellow to warn approaching motorists that the
signal is about to turn red. The length of the yellow signal depends on the
speed limit of the road. Most urban intersections have a yellow time of four to
six seconds. The yellow signal means stop if it is safe to do so. Any vehicle
travelling at the speed limit toward a green signal that changes to yellow
should have sufficient time to stop safely or clear the intersection before the
signal changes to red if the driver has entered the intersection.
All-red time
The all-red
time is the time between the end of the yellow signal on one phase and the
commencement of the green signal on the next phase. All-red time is used to
provide a safe clearance for vehicles that cross the stop line towards the end
of the yellow signal as they may be in danger of colliding with vehicles or
pedestrians starting in the following phase.
The all-red
time is based upon the physical size of the intersections and speed limit of
the road. Similar to the length of the yellow signal, the all-red time does not
change throughout the day.
The traffic
signals at each intersection can be programmed to operate in an isolated mode
or be coordinated with traffic signals at adjacent intersections to allow the
progression of traffic along the road.
In isolated
mode, traffic signals changes are driven by the vehicle loop detectors and
pedestrian push buttons at the intersection (see above). Isolated mode works
very well for intersections with low volumes of traffic, no major flow of
traffic in one direction or intersections that are a long way from each other.
The other
mode is 'coordinated'. For traffic signals to be coordinated they need two
things:
- A common signal cycle time: The signal time is the time it takes to run through one complete sequence of all the vehicle and pedestrian movements (phases) at an intersection; and
- A timing offset between the start of one intersection's main green movement and the next intersections main green movement so that vehicles travelling at the designated speed limit leave the first intersection on the green signal and reach the second intersection at the same time as its signal turns green.
The benefit
of coordinating signals is that large volumes of traffic can pass through
multiple signals with minimum delay.
The
disadvantage is that because the common cycle time is set to meet the needs of
the largest and most complex intersection in a series, signals at smaller
intersections in the series can appear to change too slowly.
When
coordinating traffic signals, the department works hard to strike balance
between allowing the progress of vehicles along the main road and keeping the
wait times for side street vehicles to a minimum.
It is a
common misconception that people have to get all the way across a road while
the WALK signal is on. This is not
true. The purpose of the WALK signal is
to inform pedestrians when they can start to cross the road.
It is the
flashing DON'T WALK signal that is timed
so that a pedestrian who leaves during the walk will have enough time to safely
cross the roadway.
Remember, if
a pedestrian leaves the footpath at the very end of the WALK signal, they will have enough time to
safely cross the road before the next movement of traffic begins.
Some
pedestrian push buttons also have an audio and tactile (touch)
component to them. These are the push buttons -called audio tactile push
buttons - that emit a beep beep sound. Visually impaired people can use the
steady beep beep sound (homing signal) to locate the push buttons. When it is
time to cross the road the push buttons produce a series of fast beeps.
The face
plate of the audio tactile push buttons also physically pulse in time with the
audio sounds produced providing the tactile part of the push button.
Traffic
engineers use the Australian Standard AS1742 and Austroads Design Guidelines to
decide which option - the installation of signals or the construction of a
roundabout - will best suit a particular intersection.
Some of the
pros and cons are:
Traffic
Signals:
- are less expensive than roundabouts to install but higher maintenance costs;
- are normally only considered for intersections with high volumes of traffic;
- use less space than roundabouts, and
- are safer for pedestrians and cyclists
Roundabouts:
- are more expensive than traffic signals to install as they usually require land resumption but they are cheaper to maintain;
- can make traffic flow more smoothly when traffic volumes are low to medium; and
- have built-in priority rule, which means that heavy traffic in one direction can tend to dominate and cause excessive delays to traffic in other directions.
In deciding
between traffic signals and a roundabout, traffic engineers will assess each
intersection, taking into account factors such as traffic volumes, available
land, needs for pedestrians and cyclists, the intersection's accident history
and the intersection's overall place in the transport network.
Traffic
signal faults can be reported by phoning the Traffic Signals Fault Line on 13
19 40.
When calling
the fault line to report a fault or raising a concern it will assist the
operator if you can supply the following information:
- The location of the traffic signals - eg. the intersection of Finucane Road, Shore Street and Delancey Street at Cleveland.
- Details of the fault/concern -eg. The green arrow to turn right from Finucane Road travelling east into Delancey Street is not working.
- At what time of day did you notice the fault? - eg. I noticed the fault on my way to work at 7.00am this morning
- Any other information that you consider relevant.
The
following example shows the coordination of three made up intersections, Smith
Street, Jack Street and Bill Street. The left hand side of the diagram shows
the actual intersections on the street. The right hand side of the diagram
shows what is known as the space-time diagram. The x-axis (horizontal)
represents time and the y-axis (vertical) represents distance along the
roadway. At each intersection, going across the page is the green and red
signals (A phases and B phases) that the drivers would see over time.
As shown in
Figure 1 below, if the car leaves Smith Street at point A it would get to Jack
Street (point B) as the signal turns green. Likewise the signal would turn
green as the car reaches point C at Bill Street. In this case the timing of the
signals is really good for the car heading north as the offsets between the
start of Smith St's green and the other intersections allows for good
northbound coordination. Click here to see an animation (MP4, 9.52 MB) | animation (WMV, 4.07 MB) | transcript (TXT, 0 KB).
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