Base Timing Definitions

SG Number

The signal group used for identifying the signal group within the controller. This number is also used for the corresponding signal group object in Vissim. The signal group numbers assigned within a signal controller must be pairwise distinct.

SG Name

The SG name is only used within the RBC graphical interface.

Min Green

Defines the minimum green time for which the signal group must remain green after turning green. Min Green must be greater than 0.

Veh Extension

Max Green 1

Defines the maximum green time that the signal group will be allowed to extend before it will max-out. A max-out will make a signal group eligible to terminate, even though it may not have gapped-out. Normally, the maximum green timer will not begin counting until an opposing call to the signal group is present. If no opposing call is present the maximum green timer will be reseted. An exception to this rule is when the signal group is a flagged as a Max Recall signal group, in which case the maximum green timer will begin counting as soon as the signal group changes to green. Max 1 is the default maximum green time for each signal group.

Amber

The time a signal group will remain an amber interval before advancing to red. This time cannot be abbreviated by any operation.

Red Clearance

The time a signal group will remain red before a conflicting signal group will be allowed to begin timing.

Ped SG Number

The number of the pedestrian signal group associated with the vehicle signal group defined in the column. If no Ped SG Number is specified, no pedestrian SG will be associated with that vehicle SG. If specified, the Ped SG Number is also used for the corresponding signal group object in Vissim. The signal group numbers assigned within a signal controller must be pairwise distinct.

Walk

The minimum time a signal group will display a walk indication before advancing to the pedestrian clearance interval (FDW). The associated vehicle SG must remain green while the pedestrian SG is in the walk interval. This parameter is ignored if no Ped SG Number is specified.

Flashing Don't Walk

The time a signal group will display a flashing don’t walk indication before advancing to solid don’t walk. The associated vehicle SG must remain green while the pedestrian SG is in the FDW interval. This parameter is ignored if no Ped SG Number is specified.

Start Up

Signal groups that will be green at the start of the simulation. By default, these signal groups will begin timing in green with walk if there is pedestrian timing defined. The signal groups flagged as Start Up must not be conflicting. If no signal groups are selected for Start Up, the first signal groups listed in the sequence will start in green at the start of the simulation.

Min Recall

Signal groups flagged for this option will receive an automatic vehicle call.

Max Recall

Signal groups flagged for this option will receive an automatic vehicle call and extension. The maximum green timer will unconditionally begin timing at the beginning of green. Without Max Recall, the maximum green timer will only time if there are opposing calls to the signal group.

Ped Recall

Signal groups flagged for this option will receive an automatic pedestrian call when they are not in walk. With Ped Recall, pedestrian signal groups only turn green together with their parent signal group.

Dual Entry

When a signal group is called in another barrier group, not all rings might have a signal group with a call in that same barrier group. In such rings, signal groups within that barrier group which are flagged as Dual Entry are considered called as well. This feature is often used for through-movement signal groups such that if one signal group is called, the opposite through movement is served as well.

Displays the walk indication for a pedestrian phase prior to the associated vehicle phase. This allows the pedestrian to enter the intersection before the vehicle enters. The pedestrian can be perceived earlier by other road users. The Manual on Uniform Traffic Control Devices (MUTCD) states a duration of at least 3 seconds for the Leading Pedestrian Interval.

Max Green 2

An alternate maximum green time for the signal group that can be used when the controller is running in a pattern.

Max Green 3

An alternate maximum green time for the signal group that is only observed if maximum timing is called for by a pattern.

Cycle Length

The cycle length of the pattern is the maximum time it will take for each signal group to cycle once. The cycle length is only used for coordination. If a cycle length is not defined (set to zero), the pattern will run in Free-Running Mode. If the cycle length is greater than zero, coordinated signal groups must be defined as well.

Offset

When coordinated, the local cycle timer will be offset from the master cycle timer by the defined offset time.

Max Green Mode

The Maximum Green Mode will be used for all signal groups while the coordination pattern is active. This selection is only valid for coordinated patterns, if used in Free-Running Mode, the value will be ignored. The selections are:

• MaxInhibit: All signal groups will ignore their maximum green timers. Signal groups will only terminate if they gap-out or reach their force-off point.
• Max Green 1: All signal groups will observe their Max Green 1 setting.
• Max Green 2: All signal groups will observe their Max Green 2 setting.
• Max Green 3: All signal groups will observe their Max Green 3 setting.

Permissive Mode

The Permissive Mode for the coordination pattern controls the method in which permissive periods are opened and closed for all non-coordinated signal groups. The controller will only yield to signal groups that are permissive following the end of green on each coordinated signal group. The Permissive Modes are as follows:

• Single Band: The Permissive Period for non-coordinated signal groups will open:

• At the beginning of the coordinated signal group green for signal groups in the same ring and concurrent barrier group as the coordinated signal group, or
• At the beginning of the lagging coordinated signal group green for signal groups outside of the same concurrent barrier group as the coordinated signal groups.

The Permissive Period for non-coordinated signal groups will close:

• When there is no longer enough time to clear all timing signal groups and serve the longer of the minimum green or permissive green on the signal group, or
• When the signal group is in a different concurrent barrier group then the coordinated signal groups and any coordinated signal group has yielded to a signal group that is sequentially before the coordinated signal group, in the same ring and concurrent barrier group, i.e. a lagging coordinated signal group yielding to its opposing left turn will close all cross street permissive periods for the remainder of the cycle.

• Multi Band: The Permissive Period for non-coordinated signal groups will open, if one or more signal groups are green or if the controller of the ring is not back to the coordinated group at the earliest time. Otherwise the permissive periods are opened at the same time as in Single Band:

• The same as single band permissive operation above, but only for the first signal group in each ring that sequentially follows the coordinated signal group.
• For each subsequent signal group, the Permissive Period will open once the previous signal group’s Permissive Period closes (only one signal group per ring can be permissive at any given time).

If a signal group changes to green, the Permissive Period of the groups that sequentially follows considered as open, it is not necessary to wait until the appropriate Permissive Periods are opened.

The Permissive Period for non-coordinated signal groups will close the same as they do for Single Band permissive operation above.

Explicit Force Offs

During an active coordination pattern, activates explicit Force Offs defined in the pattern instead of using Splits.

Explicit Permissives

During an active coordination pattern using Explicit Force Offs defined in the pattern, activates Explicit Permissive Periods defined in the pattern instead of using automatically defined Permissive Periods. These can only be used with Explicit Force Offs.

Offset Reference

This is the point in the cycle where the master cycle timer will be equal to the defined offset time when the controller is coordinated and not in transition (offset seeking). The selections are:

• Lagging Force-Off (LagFO): The reference point will be at the force-off point for the lagging coordinated signal group.
• Leading Start of Green (LeadGreen): The reference point will be at the start of the leading coordinated signal group green (the computed start of green, note that the signal group may actually return to green early if there is lack of demand on opposing movements).
• End of Lagging Red (LagEnd): The reference point will be at the end of Red Clear for the lagging coordinated signal group.
• End of Coordinated Group Red (CoordEnd): The reference point will be at the end of red for the last signal group in the concurrent barrier group with the coordinated signal groups.

Splits

The split of a signal group is the amount of time allocated in the cycle for that signal group to time. The split includes the time it will take the green, amber, and red clearance intervals to time for each signal group.

When using splits, the force-off points, yield points and permissive periods are computed automatically. Force-off points and yield points are placed so that the signal group turns amber early enough within the cycle so that conflicting calls can be served at the start of their split.

In many cases, the force-off point (or yield point) of a signal group will be placed just so that the signal group can serve its clearance before the end of its split. However, for signal groups placed just before the barrier, additional time might be required to cross the barrier, causing the force-off point to be placed earlier. This is required when the signal group might turn amber together with a signal group which has longer clearance time than the signal group itself. In that case, the longest relevant clearance time is used for computing the force-off point.

Example: Automatic force-off point computation with splits

Consider a supply with the following sequence:

The cycle length is 60 s. Each signal group has a split of 15 s. Signal groups 2 and 6 are coordinated. The force-off point of SG4 is computed as follows:

• Configuration: All signal groups in the second barrier group have Amber + Red Clearance = 5 s

Result: The force-off point of SG4 is placed at cycle second 55.

• Configuration: SG4 has Amber + Red Clearance = 5s, but SG7 or SG8 have Amber + Red Clearance = 7 s

Result: The force-off point of SG4 is placed at cycle second 53.

Reason: The controller must be able to turn SG4 amber together with SG7 or SG8 and still turn SG1 and SG5 green at the beginning of their split-allotted green time.

• Configuration: SG4 and SG8 has Amber + Red Clearance = 5 s, but SG3 has Amber + Red Clearance = 7 s.

Result: The force-off point of SG4 is placed at cycle second 55.

Reason: SG3 and SG4 cannot time together, so the force-off point of SG4 is not affected by the clearance of SG3.

• Configuration: SGs 4 and 8 have Amber + Red Clearance = 5 s, while SG7 has Amber + Red Clearance = 7 s. Signal groups 3 and 8 are coordinated instead of 2 and 6.

Result: The force-off point of SG4 is placed at cycle second 55.

Reason: Since SG8 is guaranteed to turn green in each cycle, SG4 can only turn amber together with SG8. The clearance time of SG7 is does not affect the force-off point of SG4.

Conditions for Split values:

Split values must satisfy the following conditions:

• Minimum Green must be accommodated: Within its split, the signal group must be able to serve its minimum green time before the force-off point is reached. Usually, it is sufficient to configure a Split value greater than or equal to the sum of Minimum Green, Amber, and Red Clearance times of the signal group.
• If the signal group is parent of a pedestrian signal group: Within its split, the signal group’s pedestrian SG must be able to complete the full pedestrian service time (Walk and Flashing Don’t Walk) before the parent SG’s force-off point is reached. Usually, it is sufficient to configure a Split value greater than or equal to the sum of Walk, Flashing Don’t Walk, Amber and Red Clearance.
• If overlaps are used: When an overlap signal group turns amber, the signal group that is next after the parent SG can only turn green after the overlap has finished its clearance. At this point, the parent SG might already have finished its clearance several steps ago (for example, when the overlap has more Amber time than the parent). The controller must still be able to turn the sequentially next signal group(s) after the parent SG green early enough so that they can turn amber at their force-off (or yield) point.

Example: if an overlap with parent SGs 2 and 3 was added to the supply above, and if SG4 had Amber = 3 s, Red Clearance = 2 s and Min Green = 7 s, the overlap could have at most 3 s more clearance time than SG3, because the green time allotted to SG4 by its split is 10 s and SG4 must have finished serving its min green time before its force-off point is reached.

• In total, the splits must match the cycle length: The sum of the splits of all signal groups in each ring must add up to the pattern’s Cycle Length. Here, it must be taken into account that in concurrent barrier groups that have one or more rings without any signal groups, the controller will automatically insert split time into the rings without any signal groups so that the split sums will be aligned at each barrier.

Min Green

Alternate Max

When defined for a signal group, this value overrides all maximum green times defined for this signal group when this pattern is running. This new max green time is used for both coordinated and Free-running patterns.

Veh Extension

If this is nonzero, it overrides the Veh extension value defined in the base pattern (Veh Extension).

Force Off

Defines the time in seconds measured past local zero point that selected green phase will end within local cycle. This value is only used if ExplicitForceOffs is set to On, otherwise automatic force offs are used as defined by Split and offset reference.

Permissive Start, Permissive End

This is the time period within the cycle in which a call for the signal group can be acknowledged by the controller and result in green time for that signal group if the call remains after prior signal groups with calls have cleared. This value is only used if both Explicit Force Offs and Explicit Permissives are set to On; otherwise, automatic permissive periods are used as defined by Permissive Mode. Permissive Period is defined by Permissive Start and Permissive End:

• Permissive Start: The time in seconds measured from the local zero point (defined by the Force Offs)
• Permissive End: The time in seconds measured from the local zero point (defined by the Force Offs) at which a call for the signal group will no longer be acknowledged by the controller.

Max Green 2

Signal groups that will observe Max Green 2 timing while the pattern is active. This setting is also used in Free-Running Mode.

Max Green 3

Signal groups that will observe Max Green 3 timing while the pattern is active. If both Max Green 2 and Max Green 3 are selected for a signal group, Max Green 3 will be used. This setting is also used in Free-Running Mode.

Coordinated

In Coordinated Mode, the coordinated signal groups are used to introduce an element of fixed-time control into the cycle. They are automatically called and forced to be green during the green time allotted by their splits. Coordinated signal groups are typically the main street through signal groups of a street where vehicular progression is desired.

If coordinated signal groups are not defined, the cycle length of the pattern must be 0 and controller will run in Free-Running Mode. Otherwise, coordinated signal groups must all be defined in the same barrier group. Each ring which has signal groups in that barrier group must have a coordinated signal group.

When using explicit force-offs, the yield point (that is the cycle second, in which the guaranteed green time of the coordinated signal group ends) of the coordinated signal group is the Force Off value configured in the pattern.

Ped Recall, Min Recall, Max Recall

see Timing by SG Basic Parameters (Timing by SG Basic Parameters). This will also be applied if the pattern is run in Free-Running Mode.

Veh Omit

An omitted signal group does not receive a call in this pattern. However, it can still turn green right after a transition from a pattern, where it is not omitted. During a preempt the Omit flag is ignored. The split lengths of omitted signal groups must be set to 0: The split lengths of the non-omitted signals must add up to the cycle length in each ring. A coordinated signal group must not be omitted. Phases of omitted vehicle signal groups are not shown in the timing diagram.

Max Inhibit

When the pattern Max Green Mode in pattern global setting is set to anything except for MaxInhibit, this parameter allows individual signal groups to be defined for MaxInhibit, i.e. ignore the signal group maximum green timer and only terminate by gap-out or force-off.

Lead

Allows the user to change the sequence when a pattern is running. The timing diagram will show the new sequence. If the sequence does not change for this pattern, this parameter does not need to be set. Pattern 8 uses an alternate sequence instead of Lead.

Pattern Number

This is the pattern that will run starting at the defined Pattern Start Time. The Free-Running Mode will run the Basic and Advanced timing.

Pattern Start Time

This is the start time from midnight in format hh:mm:ss, at which the defined pattern will start running. The simulation start time will be taken into account. If more than one pattern is defined for the same start time, the last listed will be the pattern that is run for that time. Active patterns will only end with another pattern begins.

Overlap SG

Signal Group numbers for corresponding overlap. The signal group number that will be created in Vissim and will be used to create signal heads that used the timing defined for this overlap.

Delay Green

TrailGreen

Amber

Red Clearance

The time an overlap will display red before any signal groups that conflict with either the overlap or its Parent signal groups can begin timing. This time cannot be abbreviated by any operation.

Parent

These are the signal groups that the overlap will be allowed to time with. When one parent signal group is timing and another parent signal group is next, the overlap will remain green (unless a negative vehicle or pedestrian signal group is next). When the last parent signal group terminates, the overlap will also terminate.

Delay Enable

An optional delay (Delay Green time) will be timed prior to the overlap changing from red to green if any signal group flagged for this option is timing.

Trail Enable

Normally when an overlap terminates, it will begin timing its amber clearance interval. An optional green clearance interval (Trail Green time) will be timed prior to the amber clearance interval if any signal group flagged for this option is timing. This is commonly used at intersections where an overlap controls a movement that cascades one or more signal groups and requires addition travel time from the movements controlled by the Parent signal groups.