Traffic lights

You can report a problem with a traffic signal by calling the Traffic Signals Fault Line on 1300 139 933 or by emailing traffic.signals@stategrowth.tas.gov.au.

If you are reporting a traffic signal fault that is causing a safety hazard, you must call our fault line. The fault line operates 24 hours a day, every day of the year. People are available at any time to fix safety issues.

The email address is only monitored during normal business hours, 9:00 am – 5:00 pm Monday – Friday.

When reporting a fault or concern it will help us fix the issue quickly if you can tell us:

• the location of the traffic signals – the 4 digit number on the controller box, or the street names
• details of the fault/concern
• when you noticed the fault
• any other information that you consider relevant.

We use the Sydney Coordinated Adaptive Traffic System (SCATS) to:

• coordinate traffic signals
• record faults (such as blown lights)
• record data for performance monitoring (eg. traffic counts at intersections)
• manage traffic incidents and special events

Many of the traffic signals throughout the state are connected to a central system which registers and logs faults as they occur.

We monitor these logs and organise the repair works.

There are many signals around the state that are not monitored by the central system. We rely on information from the public to find out about faults at these sites. Once we know about an issue, we will attend to it quickly.

If you would like a new set of traffic signals installed on a State road, you can send your request through to us at info@stategrowth.tas.gov.au.

If you would like a new set of traffic signals on a Council road, you should send your request through to the relevant council.

Find out which roads are State roads on the State road network map

The main reasons to have traffic signals are:

• to allow road users to safely move through an intersection
• to give priority to a particular direction or mode of travel at different times of the day
• to let large amounts of traffic to pass through the network with minimal delay by coordinating signals.

A standard set of traffic signals consists of:

• a traffic signal controller
• vehicle detector loops and pedestrian push buttons
• traffic signal lights
• posts, pits and underground electrical cables that connect all the components together.

The traffic signal controller

The traffic signal controller is a computer controlled device that processes information received from the detector loops and pedestrian push buttons. It changes the lights based on its programming.

The controller sets how long the light is green for each traffic movement, and controls the change from one combination of lights (known as a phase) to the next.

It can operate in a 'standalone' way, or it can be programmed to coordinate with a series of nearby traffic signals.

Vehicle loop detectors and pedestrian push buttons

Vehicle loop detectors and pedestrian push buttons make the controllers 'see' them, and change the signal to give them right of way.

Vehicle loop detectors are loops of wire that work as a metal detector, buried in the road near the stop line at the intersection. When a vehicle is passing over the loop the magnetic field (inductance) of the loop changes. The controller is told that a vehicle is waiting to go through the intersection.

When the pedestrian push button is pressed the controller knows that a pedestrian is waiting to cross.

Traffic signal lights

Traffic signal lights are how the controller directs traffic. They tell the road users when to go and when to stop.

Tasmanian 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
• RED = Stop.

Signal phases and cycles 

Each combination of green, yellow and red lights is called a phase. Each phase has a programmed minimum time. Once the signals have entered a phase they can’t change again until the minimum time has ended.

One full sequence of all the vehicle and pedestrian movements (phases) at an intersection is known as the signal cycle. The cycle time varies by location and time of day.

The yellow light

Traffic lights change from green to yellow to warn people that the signal is about to turn red.

The length of the yellow light depends on the speed limit of the road.

The yellow light 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 enough time to stop safely. If the driver has entered the intersection, they should have time to leave the intersection before the signal changes to red.

All-red time

The all-red time is the time between the end of the yellow light on one phase and the start of the green light on the next phase.

All-red time provides a safe clearance for people that cross the stop line towards the end of the yellow light, 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 light, the all-red time does not change throughout the day.

When the green pedestrian signal is displayed, pedestrians can begin to cross the road with care

The flashing red pedestrian signal means pedestrians who have already begun crossing during the green pedestrian signal can finish crossing.

Pedestrians must not begin crossing when the red pedestrian is flashing.

The steady red pedestrian signal means pedestrians should not begin crossing. Instead, pedestrians should press the button and wait for the green pedestrian signal.

The traffic signals at each intersection can be programmed to work in an isolated mode or be coordinated with traffic signals at nearby intersections to let traffic move along the road in ‘platoons’.

In isolated mode, traffic light changes are caused by the vehicle loop detectors and pedestrian push buttons at the intersection. This mode works very well for intersections without much traffic, if there’s no major flow of traffic in one direction, or on 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.
• A difference in time 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 intersections with short delays.

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, lights at smaller intersections in the series can appear to change too slowly.

When coordinating traffic signals, the Department works hard to strike a balance between allowing the progress of vehicles along the main road and keeping the wait times for side street vehicles to a minimum.

The following link on the Queensland Department of Transport and Main Roads website explains how signals can be coordinated. It also provides an insight into the complexities and challenges in coordinating signals, especially across a number of intersections.

http://www.tmr.qld.gov.au/Travel-and-transport/Road-and-traffic-info/Traffic-Signals-Information#Coordination

The Department is also responsible for the control and maintenance of electronic school zone speed signs. However, the operating times for each school zone are nominated by the relevant school to reflect the peak periods of activity.

If you need further information on traffic signals please contact info@stategrowth.tas.gov.au.