Table of Contents

6.3.2 Traffic Signal Techniques to Support Road User Priorities

Traffic signals are one of the tools that can be used to implement road user priorities in a network operation plan. The various traffic signal techniques can be categorised as techniques that support:

The selection of the most appropriate traffic signal technique to support a network operation plan involves an evaluation of a set of short-listed techniques. The evaluation of these treatment options can be done by ‘network fit assessment’, described in the Guide to Traffic Management Part 4 (Austroads 2016a). Figure 6.3 illustrates two examples of a network fit assessment result. The left example shows the assessment of a technique that has positive impacts for trams and negative impacts for general traffic as well as buses. On the right is a technique that has positive impacts for general traffic but has negative impacts for buses. The decision on the technique to implement would depend on which addresses the performance gap and the needs of targeted road user groups.

It should be noted that a traffic signal technique can have impacts on other road user groups, as exemplified in Figure 6.3. These impacts can include mobility, safety and to some degree access (i.e. in case of restricted movements). These trade-offs in performance need to be understood in order to conduct network fit assessment. The impacts of treatments on performance gaps are assessed typically through expert-panel judgment. Traffic modelling is applied if resources are available and if a more detailed assessment is desired to give greater confidence in the outcome.

The report Signal Management Techniques to Support Network Operations (Austroads 2015e) has developed a toolkit to assist in understanding the scope and scale of impacts of traffic signal techniques. This toolkit (Appendix L) can be used as a reference when conducting a network fit assessment of traffic signal techniques.

Figure 6.3: Examples of a network fit assessment

Source: VicRoads (2013c).

Traffic management considerations at signalised intersections may involve the allocation of road space or lanes to specific road user groups. These are discussed in Part 6 of the Guide to Traffic Management (Austroads 2019c). Part 10 of the Guide to Traffic Management (Austroads 2019d) provides guidance on signal displays and the locating of equipment relating to the modal treatments described.

Many of the modal treatments described in this section may involve complex signal operations. These will require input from specialist signal operations engineers who can provide advice on appropriate phasing sequence options, associated model inputs or other critical elements.

Table 6.2: Signal timing and phasing treatments that support general traffic priority

Traffic signal treatmentDescription
Improved signal coordination/progressionCoordinate offsets between different signals to improve progression for general traffic.
Banned right-turnsProhibit right-turns to improve through movements (either permanently or at peak times).
Skip right-turns every second cycle (peak times)Skip right-turns every second cycle to improve through movements (e.g. at peak times).
Maximum time transfer/stealingAlthough each phase has only one maximum time setting, the maximum time of a given phase can be increased by transferring maximum time from other phases. This provides an automatic method of adjusting the relative allocation of maximum time where traffic flow is particularly tidal.
Gating to an areaControl the inflow and outflow of traffic to prevent serious congestion in sensitive areas where it is particularly important (e.g. city centres). May use downstream detection to lessen the throughput of upstream traffic into a congested area.
SCATS Incremental Split Selection and Variation Routine 83 (for congestion management)Specific SCATS routines for congestion management. Included in VR83, a spill-over flag is introduced to modify the degree-of-saturation values used for the calculation of signal timings when downstream queue blocking occurs.
Pedestrian parallel walkPedestrians cross in parallel with the through traffic movement. Vehicular signal green periods and pedestrian walk periods commence at the same time, with drivers required to give way to pedestrians when turning left/right across the crossing.
Late start for vehicles (early start/leading interval for pedestrians) – partially protected parallel walk

Pedestrian phase is started prior to parallel vehicle phases. Vehicular traffic is prevented from turning across the crossing for the initial part of the pedestrian walk period (i.e. through use of red arrows), subsequent to which, vehicles are allowed to proceed subject to them giving way to pedestrians on the crossing. Hence, pedestrians are protected from turning traffic for the initial part of the crossing period. The late start for vehicles may be implemented as an active measure (e.g. only when pedestrian demand detected).

An often used alternative is to restrict turning movements for the full duration of the pedestrian phase, hence this treatment is classified as supporting general traffic.

Pelican crossingTypically used at mid-block crossings. Applies a flashing yellow phase that enables vehicles to proceed once pedestrians have cleared the crossing. Helps to minimise delays resulting from the flashing don’t walk interval operating when no pedestrians remain in a pedestrian crossing.
Two-staged crossing at wide intersectionsProvide safe crossing options for pedestrians, while also ensuring vehicular traffic is cleared in time. May be cleared in a single phase or two. Push buttons may be available in the central waiting area to register demand.

Source: Austroads (2015e).

Table 6.3: Signal timing and phasing treatments that support public transport priority

Traffic signal treatmentDescription
Green extension/phase extensionTraffic signal extends green period when a bus or tram is approaching to assist with clearing the signalised intersection prior to the red period.
Recall/red truncation or early green/priority green/phase early‑startWhere a bus or tram is expected to arrive prior to a green phase, the red phase is terminated early and signal phases are reconfigured to allow the green phase to begin earlier.
Additional phase in signal cycle to clear queues in front of buses/tramsThe additional phase is used to clear queues in front of buses or trams so that they can progress through the intersection upon arrival.
Priority phase sequencesA sequence of phases (e.g. special phases and phase extension) may be called to clear traffic from the path of a bus or tram prior to the actuation of the public transport vehicle priority phase itself.
Phase suppression (of conflicting movements)Phase suppression, or omission of a standard phase in the signal cycle, may occur when a bus or tram priority phase is called. This promotes the allocation of priority to the public transport vehicle. The conflicting movement would be supressed in order to favour the primary movement.
Public transport priority phase with dedicated lanes (full-time or part‑time)Public transport vehicles are detected on a dedicated (permanent or peak-period only) public-transport-only lane, which activates a priority phase that only buses or trams can complete. Also may be referred to as special phase/bus-only phase/tram-only phase.
Public transport priority phase with queue-jump lanesPublic transport vehicles are detected on queue-jump lanes, which activates a priority phase that only buses or trams can complete. Queue-jump lanes are shorter sections of bus-only lanes/tram-only lanes on the carriageway on approach to intersections.
Priority movement repetition in cycleThe movement required by buses or trams is introduced at more than one point in the signal cycle. This technique may be particularly useful at complex intersections with multiple phases and/or long cycle times, and where public transport vehicles cross a major road.
Reduced cycle timeReducing the cycle time to shorter than that dictated by general traffic can reduce the delay experienced by public transport vehicles. This technique may be particularly effective where public transport vehicles have dedicated lanes and their frequencies are high.
Gating to an area for queue managementControls the flow of vehicles through the area surrounding critical intersections on a public transport priority route. Improves public transport vehicle travel time, for example by reducing the demand for green time from other traffic movements at critical intersections.

Source: Austroads (2015e).

Table 6.4: Signal timing and phasing treatments that support freight or heavy vehicle priority

Traffic signal treatmentDescription
Longer signal cycle times (higher minimum cycle times)A longer cycle time generally favours truck movements as long as the green time ratio is maintained. A longer cycle time typically can provide a longer green period in a cycle, which allows more vehicles including trucks to pass through an approach irrespective of a truck’s position in a platoon. Longer cycle times also minimise the need for trucks to stop and start.
Coordinating signal offsets for heavy vehiclesSelecting offsets to minimise trucks from stopping along an arterial road.
Green extension/dwell phase extension/early startTraffic signal extends green time to assist heavy vehicles with clearing a signalised intersection. Similar to active priority for public transport, e.g. equip with GPS/transponders or other heavy vehicle detection systems in order to extend or bring forward (i.e. early start) a green phase on detection of approaching truck and to minimise stops.
Ensure that heavy vehicles are able to move from the stop-line and safely clear the intersection

Increasing of clearance times.

Refer to Commentary 11.

Source: Austroads (2015e).

Table 6.5: Signal timing and phasing treatments that support bicycle priority

Traffic signal treatmentDescription
Late start for vehicles (early start/leading interval for cyclists)Bicycle phase is started prior to parallel vehicle phases. An early start positions cyclists where they are more likely to be noticed by motorists when a parallel vehicle phase begins. Typically, the vehicle late start would only be activated if a bicycle is detected (i.e. on a bicycle lane). May be more effectively implemented with lead-in lane and advanced stop boxes.
Fully protected parallel crossing for cyclists at shared path crossingGreen/red (ride/don’t ride) bicycle signals are displayed concurrently with the operation of green/red (walk/don’t walk) pedestrian signals at a protected parallel shared path crossing. Typically, the cyclist or pedestrian on a shared crossing would be required to press a call button to activate the crossing.
Extended clearance intervalsThe clearance time for a bicycle movement may need to be longer than for other traffic (i.e. early cut-off of cyclist movement). A cyclist may travel slower than other vehicles and may not have sufficient time to safely clear an intersection when entering just before the yellow interval. Requires bicycle signal aspects to be used. Can be implemented as a passive and active measure (e.g. via a detector in a bicycle lane).
Longer green time for cyclists at shared path crossingsAt shared path crossings, cyclist signals may have a longer green time and a shorter clearance time than pedestrian signals (while the total phase time remains the same), since cyclists move faster.
Exclusive signal phase for cyclistsSimultaneously preventing vehicular traffic on all intersection approaches from entering the intersection to allow cyclists exclusive crossing access.
Activation of green signal phase when cyclists are detectedDetection of cyclists results in activation of green signal bicycle display. Detection may be via cycle request boxes/push buttons or loop detectors. Loop detectors may be installed along cycle routes on approach to major intersections, in cycling facilities adjacent to other traffic lanes, or in advanced stop boxes.
Signal coordination for cyclist priorityIn some situations, traffic signal coordination may be provided for the benefit of cyclists. May be considered in specific situations such as on bicycle routes with high cyclist volumes, several closely spaced signals, and a strong tidal flow.
Arterial reversionIn the absence of demands, the traffic signals will revert to a selected stage (e.g. a signal plan for a cycle priority route).
Cyclist bypass lanes at T‑intersectionsProvide cyclists travelling on the mainline with a green bicycle display at a T-intersection if the side street turning vehicles do not conflict with the cyclist facility at the intersection.
Mid-block crossing signals for cyclistsProvide cyclists with bicycle signal aspects at mid-block pedestrian crossings so that they are not required to dismount.

Source: Austroads (2015e).

Table 6.6: Signal timing and phasing treatments that support pedestrian priority

Traffic signal treatmentDescription
Exclusive signal phase for pedestriansSimultaneously preventing vehicle traffic on all intersection approaches from entering the intersections to allow pedestrians exclusive crossing access. Pedestrian phase is not timed for the diagonal movement. Suitable locations include near major pedestrian-use facilities such as transport interchanges, major sporting/entertainment venues and shopping complexes.
Exclusive ‘scramble crossing’ or ‘Barnes dance’ phaseAllows all pedestrian movements, including diagonal movements, to operate simultaneously within the marked limits of the crossing while eliminating vehicle conflicts. Pedestrian phase is timed for diagonal (longest) movement and operates as an exclusive signal phase. Scramble phasing eliminates conflict between pedestrians and turning vehicles and consolidates all pedestrian movements at an intersection into one phase. They are generally good for areas with high pedestrian and turning vehicle volumes.
Double/half cyclingIn areas where traffic signals are coordinated and there are high pedestrian volumes, a minor intersection or mid-block crossing may use a cycle time that is half the length of adjacent signals. Reduces pedestrian waiting time, while still allowing for traffic signal coordination.
Dwell on red for all users, or dwell on walk (green) for pedestriansTraffic signal displays red for all movements until a pedestrian (or vehicle) is detected. Alternatively, a traffic signal dwells on the pedestrian walk interval until a vehicle is detected. May be appropriate during situations where pedestrian volumes are high and vehicle volumes are low (e.g. late at night near areas of alcohol consumption).
Extended clearance intervalsLengthen clearance intervals for pedestrians at high-volume crossings (e.g. midblock crossings outside schools). Can use active detection.
Extended walk/stretch walk/rest in walkThe pedestrian walk interval is kept as long as possible with the parallel vehicle green signals.
Reduced cycle lengthsReduce cycle lengths to reduce waiting time for pedestrians in areas of high pedestrian activity (e.g. city centres).
Fixed demandController is set to register demand for a pedestrian movement on every cycle. Should only be considered where and when pedestrian volumes are high (e.g. city centres) to avoid pedestrian phases when there is no pedestrian demand.
Puffin crossingAdditional detectors monitor the progress of pedestrians on a crossing, allowing crossing time to be reduced when a pedestrian has crossed quickly, or extended for slow-moving pedestrians. May aid slower-walking pedestrians and minimise delays due to flashing don’t walk interval operating when no pedestrians remain on a crossing. May also apply kerbside detectors to cancel a pedestrian call when pedestrians are no longer present during the walk interval, in order to minimise unnecessary delay to vehicles. Also implemented as intelligent mid-block pedestrian activated crossing. Typically implemented at mid-block crossings.
Isolated traffic controls at areas with high pedestrian demandThe traffic control is isolated instead of being coordinated with others, which may reduce pedestrian wait time by decreasing the signal cycle time or skipping phases. Generally applied to coordinated signals with very long cycle times, where pedestrian level of service is determined to be of higher priority. May only be applicable to certain times of day.
Pedestrian countdown timersCountdown timers show the time remaining until the end of the pedestrian clearance interval in order to improve pedestrian behaviour at traffic signals and potentially reduce pedestrian delay. Countdown timers may also count down until the next walk interval; however, this type of countdown timer has not been trialled in Australia or New Zealand.
Reintroduction of pedestrian walkPedestrian walk interval is reintroduced after the pedestrian phase has timed out on the main road phase, but there is no traffic on conflicting phases.

Source: Austroads (2015e).