6Systems and procedures for arterial traffic control – traffic signals#

6.5Movements and phases#

6.5.2Phase intervals#

Pedestrian Countdown Timers#

This section defines recommended practice on the application of pedestrian countdown time (PCT) displays in Queensland and supplements guidance contained in the following Austroads publications:

• Austroads Guide to Traffic Management
• ― Part 6 Intersections, Interchanges and Crossings Management
• ― Part 9 Transport Control Systems – Strategies and Operations, and
• ― Part 10 Transport Control – Types of Devices.

Background#

'Standard' pedestrian signals at traffic signals and pedestrian-actuated crossings provide a short green WALK period for pedestrians to commence crossing, followed by a clearance flashing red DON'T WALK period of sufficient time to allow pedestrians to complete the crossing before a steady red DON'T WALK period and a commencement of a conflicting vehicle green phase. Under this operation, the Queensland Road Rules permit pedestrians to commence crossing during the green WALK period only.

While the standard sequence generally serves pedestrians well at most locations, an issue can arise at locations with high pedestrian demand. At these sites, due to high pedestrian volumes, it is common to see pedestrians start to walk and complete the crossing well within the relatively long clearance flashing DON'T WALK period that is required to cater for the less able-bodied pedestrians to complete their crossing.

The PCT display provides information to pedestrians on remaining duration of the pedestrian clearance phase. PCT safety and efficiency relies upon pedestrians being able to judge for themselves how much time they need to complete the crossing if they commence to cross during the PCT sequence. PCTs appear to increase pedestrian amenity. There is currently limited evidence regarding PCT safety benefits.

Applicability#

PCTs can only be used where pedestrian clearance times are fixed and are most appropriate at scramble crossings or mid-block crossings. Pedestrian-responsive traffic signals incorporating pedestrian detection technology, also known as Smart Crossings (refer Smart pedestrian crossings guideline) are preferred over PCTs due to operational benefits realised for all road users. PCTs are incompatible for use in conjunction with smart pedestrian crossings, as the clearance times vary, based upon pedestrian presence.

To maximise the benefit for pedestrians while providing an appropriate level of safety, the following criteria should be considered to determine whether PCTs are appropriate:

• PCTs should only be installed at crossings where the countdown timer period is greater than six seconds as providing PCTs at locations with short clearance times provides little or no real crossing benefit for pedestrians.
• PCTs are potentially most appropriate in areas with high pedestrian demand: for example, CBD, shopping precincts, public transport hubs.
• In some cases, PCTs can result in increased delays for turning vehicles, as more pedestrians cross during the clearance period. As a result, the impact on efficiency may need to be considered at intersections with high volumes of turning vehicles.
• PCTs should not be used at crossings predominantly used by primary school children – it is considered that some school children may not be sufficiently well-developed to estimate the distance required for them to cross during the PCT or to understand the risk of crossing too late and continuing to walk during the steady red DON'T WALK.

Operational issues#

On controller 'start up', the PCT unit needs to learn the applicable clearance time. During the initial cycle, the PCT will show a standard sequence flashing red DON'T WALK (symbol).

As much as possible, PCT displays should be shielded from the view of approaching drivers and unintended pedestrian movements by lantern positioning or by the use of extended length visors.

Installation requirements#

PCT displays shall be installed in accordance with requirements set out in the Queensland MUTCD Part 14 Traffic Signals.

Where PCT displays are installed, the G9-Q10_2 adhesive label shall be positioned above the top of the pedestrian push-button. This label replaces the CROSS WITH CARE (G9-Q10_1) adhesive label usually installed at signalised crossings.

6.5.3Phasing design#

Pedestrian protection#

Pedestrian protection will be provided at all intersections. The length of the timed protection period shall be as follows:

• pedestrians should be protected for the walk period as a minimum, and
• full protection should be provided in the situations listed following:
• where indicated in Austroads Guide to Traffic Management (restricted sightlines, high speed and two turning lanes)
• in activity-based places in the movement and place framework (some movement and significant place aspects)
• at Smart Crossings where carriageway pedestrian detectors have been provided (these ensure pedestrian protection is provided only while pedestrians are on the crossing), and/or
• in accordance with the requirements of Austroads Guide to Traffic Management Part 9 Section 6.5.3.

Control of right turn movements#

There are factors to consider in controlling right-turn movements.

• Number of lanes: Bicycle lane shall be counted as a traffic lane when considering the risk factors for filter turns. A right-turning lane from an opposite approach shall be counted as a traffic lane when considering the risk factors for filter turns if it is at all offset to the right of the right-turn lane.
• Road safety: Low demand periods are the period when the majority of opposing-turning crashes occur. Consideration for all movements and users of the intersection shall be taken into account.
• Time of day: Low demand periods are the period when the majority of opposing-turning crashes occur. Consideration for all movements and users of the intersection shall be taken into account.

The usual method of allowing part-time full control at certain times of the day is to include a data parameter in traffic signal plan data which controls whether the arrow is allowed to drop off or not. In TRAFF controllers, this is usually the Z+ or Z- signal. The default mode of operation for the controller must be full control of the right turn. Filter turns are only permitted when the controller is running a plan with the relevant signal or flag. Where there is concern that a plan which allows right turn movement(s) to filter may be called at a time of day when the right-turn filtering is not appropriate, alternative arrangements, or not using part-time filter control, must be considered.

Provision of U-turns at traffic signals#

U-turns should only be permitted at signalised intersections where:

1. a)the intersection approach has a raised median
2. b)the approach has an auxiliary right-turn lane
3. c)geometry is sufficient to allow the U-turn to be made in one continuous manoeuvre by vehicles of the type likely to turn
4. d)there is adequate visibility of approaching vehicles
5. e)there would be no danger to pedestrians
6. f)there are no more than two lanes of opposing through traffic
7. g)there is no left-turn green arrow (signal) control in the road to the right
8. h)a fully-controlled right-turn phase is provided: Items (d) and (f) previously may not be relevant, and/or
9. i)there is sufficient width for a vehicle to wait to turn clear of through traffic and the lack of an auxiliary right-turn lane would not affect traffic flow and cause delays and crashes.

U-turns should not be provided at signalised intersections where:

1. a)the intersection is a very high volume intersection
2. b)the provision of U-turns at the signals alters phasing arrangements at the intersection, adversely affecting good progression along the route
3. c)their provision would significantly affect safety or traffic operating conditions at the signals (for example, delays)
4. d)their introduction would cause an unexpected conflict with pedestrians or motor vehicles, for example, with a left-turn green arrow (signal) control in the road to the right
5. e)the right-turn volume is substantial and U-turn movements represent 65% or more of the total right-turn volume
6. f)there is adequate opportunity either upstream or downstream of the signals to safely carry out a U-turn at a median opening, and/or
7. g)right turns have been generally prohibited along the route (for example, due to limited road width) and access is provided by means of alternate ‘loop’ routes instead, unless the intersection is important from a road network perspective and a U-turn can be properly provided.

Refer to the Road Planning and Design Manual, Austroads Guide to Road Design and the Austroads Design Vehicles and Turning Path Templates for geometric design requirements.

U-turns at traffic signals (when permitted by the U-TURN PERMITTED sign R2-15) should only be permitted when a green circle aspect or green signal right turn arrow is displayed.

6.7Traffic signal controllers#

6.7.1General#

Traffic signal controllers in Queensland#

Reference to the Area Traffic Control (ATC) system recognises different systems in operation in Queensland, such as STREAMS or SCATS. As such, any mention of SCATS can be read as either STREAMS or SCATS.

In addition to Appendix F of Part 9 of Austroads Guide to Traffic Management, guidance in electrical design is available in the Traffic and Road Use Management (TRUM) manual Volume 4 Intelligent Transport Systems and Electrical Technology Part 3 Electrical Design for Roadside Devices.

Location#

Controllers must be located so access can be gained for maintenance purposes. A ground-mounted controller has only one door for access. This type of controller is normally located adjacent to the property boundary, with the door opening towards the footway. The location of the controller is also affected by other conditions. Ideally, the controller should be located so that:

• a continuous 230 V single-phase power supply can be conveniently obtained (some poles cater for roadway lighting or high voltage supply only)
• a Telstra line is available nearby for STREAMS communications
• it is clear of high-voltage poles and cabinets with electrodes or earth grids as this can affect the electronics in the controller
• it is clear of future widening proposals
• the position does not detract significantly from the visual quality of the streetscape (painting in a decorative way may be appropriate)
• there will be an unobstructed view of all approaches to the site for timing and maintenance purposes
• it does not unduly obstruct the footway
• it will not be unduly exposed to accidental damage by passing traffic, and
• access is available for maintenance personnel to park a vehicle.

If it is located where it is vulnerable to traffic, it must be protected by an appropriate safety barrier. It is preferable to find a less vulnerable location and avoid introduction of another hazard (safety barrier).

6.7.2Types of control#

Types of control in Queensland#

In Austroads Guide to Traffic Management Part 9 Section 6.7.2, the ATC can be STREAMS or SCATS as determined by the road agency.

6.7.6Display duration facilities#

Display duration facilities in Queensland#

Add the following dot point:

• Connection to the ATC System, such as STREAMS or SCATS via either:

6.7.10Controller programming#

Two-aspect signal controls of pedestrian crossings on slip lanes#

This section provides advice about the use of two-aspect signal control of vehicles at signalised pedestrian crossings on slip lanes and guidance on their installation and operation.

Principles#

Two-aspect (yellow-red) vehicle signals may be used to control traffic on a slip lane, allowing pedestrians to cross on a green WALK pedestrian signal. This arrangement should generally be used where signals are required, as it results in significantly-reduced delay for both pedestrians and left-turning traffic.

The use of two-aspect (yellow-red) vehicle signals at a slip lane allows traffic to be stopped using the usual yellow-red sequence, but there is no green display. When the traffic signals are not showing red or yellow, traffic on the slip lane is required to give way to all other traffic at the intersection.

Disadvantages of three-aspect control of vehicles on a slip lane#

The slip lane cannot be given a green signal if there is any conflicting traffic, including traffic filtering right from the opposite approach. This can result in significant delays to the left-turning traffic which can be perceived as unnecessary, frustrating drivers, and often leading to a high rate of non-compliance by both traffic and pedestrians.

If the left turn is signalled green when the adjacent through movement is green, the right turn from the opposing approach cannot be allowed to filter. This results in considerable additional delay to other road users and reduces the capacity and design life of the intersection.

Pedestrian non-compliance at signalised slip lanes#

Slip lane pedestrian signals need to respond quickly to pedestrian demand, otherwise they will result in a high level of pedestrian non-compliance which undermines the safety benefit of treatment.

Guidelines for design#

The signal layout used should conform with the design principles of the Austroads Guide to Road Design. Specifically, signals should be placed in positions to provide stopping and starting functions. A primary signal should be provided, nominally 3 m from the left-hand end of the stop line. A dual primary (right-hand primary) lantern is desirable to reinforce the stopping position and to provide better sight lines for approaching traffic. Secondary and tertiary lanterns should be provided so that at least two lanterns are visible from the stop line. Arrowed lanterns or inserts should be used in all left-turn lanterns if there is confusion with the through movement lantern control. Pedestrian lanterns and push buttons should be located in accordance with Austroads Guide to Road Design and the Queensland MUTCD Part 10 Pedestrian control and protection.

Sufficient distance should be allowed between the stop line and the give way or merge lines to ensure drivers understand the need to give way at the merge point. There should be space for at least a single vehicle past the crossing (to reduce the potential that vehicles queue on the crossing). Guidance on signing and marking the merge point is given in Part 2 of the Queensland MUTCD. A give way sign may be provided if indicated by Queensland MUTCD.

Phasing arrangement#

While details of the signal group operation for the slip lanes should be site-specific, the general principle is to let the slip lane vehicle signals go to red at any time. Consideration can, however, be given to excluding the period when the parallel through movement has just started – that is, during the intergreen preceding and the minimum green periods of the parallel through movement. The decision to do this would be based on the geometry of the intersection, the length of any short left-turn lane and the probability of it queueing back and restricting the flow of the through movement.

It should be noted that pedestrians would almost always have to push a button to cross the slip lane and another to cross the main carriageway. Consideration should be given to the use of signs advising pedestrians to press the second button to cross the subsequent crossing (R3-Q01 WALK TO ISLAND AND WAIT FOR FURTHER SIGNAL).

Wherever possible, the minimum green for traffic on the slip lane should be set to allow pedestrians to cross the slip lane at least two points in each cycle of the intersection signals.

6.8Traffic detection#

6.8.3Detection system functions#

Detector logic#

Vehicles can be detected during two parts of the traffic signal cycle. Traffic waiting for a green signal registers an initial demand that it requires right-of-way (call); provided advance detectors are no closer than 15 m to the stop line, the controller can increment the initial green time. Traffic already given the right-of-way via a green signal registers its continuing requirement for right-of-way so that the green signal can be extended, depending on the prevailing traffic conditions (extend).

Detector logic is used to specify the conditions under which an actuation from a detector can call, extend, or increment a phase; for example, the standard detector logic for a stop line detector is:

• call a phase except while it is green, and
• extend a phase while it is green

and for an advance detector is:

• call a phase except while it is green
• extend a phase while it is green, and
• increment initial green except while it is green.

Using this logic, there is only one phase involved and only one condition for each function. This logic is sufficient for a simple two-phase design but, for most other types of phasing, several conditions may be required and a detector may demand and/or extend more than one phase. When designing detector logic for these situations, the basic aim is to minimise the cycle time while satisfying all the traffic and safety needs of the intersection.

This is achieved by:

• avoiding the introduction of unnecessary phases by only registering and maintaining required demands
• demanding a phase that satisfies the most (or main) vehicle movements
• minimising the variable initial green time by allowing detectors to increment when a queue is forming, and
• avoiding unnecessary extension of a phase: for example, by ceasing extension by vehicles on a given movement when that movement also runs in the following phase.

6.8.9Pedestrian detection#

Smart pedestrian crossings in Queensland#

Refer to Transport and Main Roads guideline Smart pedestrian crossings.