ITE Journal May 2018 - 37

Free Operation
Free operation is another strategy that can be used to reduce
pedestrian delay compared to coordinated operation. By removing
holds on coordinated phases, the traffic controller is able to
serve whichever phase is requesting service based on the rules of
actuated control, that of call and extend operation. Free operation
generally results in the least amount of delay for all users, but many
practitioners find it to be a less desirable option because it does not
prioritize arterial corridor movement.
There is limited research on the impacts on pedestrians of
operating the signal in free mode compared to traditional coordination. Kothuri et al. evaluated the impacts of coordination vs.
free operation via micro-simulation and found that pedestrian
delays are significantly reduced for minor-street phases during free
operation. Using field derived inputs, volume to capacity ratios for
the major-street and pedestrian phase actuations for the minorstreet (proxy for pedestrian demand), Kothuri et al. proposed a
methodology for determining if a signal should be coordinated or
free, considering overall delay across all users at an intersection.11
Free operation may be best suited for intersections with long
spacing (quarter mile or more) to adjacent signals especially when
traffic v/c ratios are less than 0.5. It can also be applied at any intersection based on a time of day approach, in order to prioritize minor-street
pedestrian movements. Free operation may be used during the off-peak
periods to reduce pedestrian delays as well as during late-night hours
when traffic volumes on the major-street are low, a strategy that has
been followed by the City of Portland, OR, USA. It may also be best
suited for intersections where the volumes on the intersecting streets

are more balanced, presuming max times are set appropriately to
prevent any movement from lengthening the cycle excessively.
Actuated-Coordination
Actuated-coordination is a signal timing treatment that allows the
user to actuate a portion of the coordinated split.2 This allows the
coordinated phases to gap out if there is low demand during the
actuated portion, thus allowing the signal to be more responsive to
field conditions than traditional coordination. This additional time
can be used by the minor-street or left turn phases. Figure 3 shows
the ring-and-barrier diagram for actuated-coordination. In Figure
3, the latter portion of coordinated phases 2 and 6 are actuated and
can terminate if there is low demand, while serving phases 3, 7, 4,
and 8 earlier.
Research on the impacts of actuated-coordination showed a
decrease in v/c ratios and fewer occurrences of split failures and a
decrease in pedestrian delay.12 Additionally, use of fully actuatedcoordination and fixed force-offs also reduced minor-street delays.
This strategy may be most useful when agencies want their
intersections to remain in coordination, even during off-peak
periods. The greatest benefits may be seen during periods when
the major-street demand is low and minor-street demand is high.
However, presence of mainline detection is necessary for implementation. The increased cost of additional detection and maintenance,
and the arrival of the major-street platoon should be carefully
considered prior to implementing this strategy.

Signal Timing Manual, 2nd Edition

Increasing Permissive Period
Permissive period refers to the period of time during the
coordinated cycle in which calls on the conflicting (non-coordinated) phases will result in phase transition from coordinated
to non-coordinated phase.7 Previous research has shown that
increasing permissive period length resulted in statistically
significant lower pedestrian delay.9 De Castro-Neto showed that for
low volume conditions having the permissive period close later in
the cycle was better for non-coordinated phases.10
Vehicular delays for the coordinated phases may be impacted
depending on the magnitude of change in the permissive period,
however, if the coordinated platoon arrives condensed and early in
the coordinated green, any increase in delay should be minimal.
More research is needed to fully understand these impacts.
Pedestrian and vehicular delays for the non-coordinated phases
may be reduced as a result of increase in permissive period.
This strategy may be best suited for implementation on a time-of
day basis as a tool to reduce pedestrian delay for the non-coordinated phases during the off-peak periods in a coordinated system.

Figure 3. Actuated Coordinated Operation
w w w .i t e.o r g

May 2018

37


http://www.ite.org

Table of Contents for the Digital Edition of ITE Journal May 2018

President’s Message
Director’s Message
People in the Profession
ITE News
ITE, FHWA, and Carmanah Rally to Keep Rectangular Rapid-Flashing Beacons in Our Safety Toolbox
Improving Arterial Roads to Support Public Health: How Can We Do This?
ITE’s Transportation and Health Initiative
Technical Programs Division Spotlight
Industry News
Calendar
Where in the World?
Member to Member: Jing Zhang, AICP, PTP, LEED AP ND
Countermeasures Prove Effective in Reducing Bicycle Collisions
Guidance on Signal Control Strategies for Pedestrians to Improve Walkability
Factors Affecting Vehicle Passing Distance and Encroachments While Overtaking Cyclists
Measuring the Success of Modal Shift: The Impact on Last Mile Connectivity
Professional Services Directory
ITE Journal May 2018 - 1
ITE Journal May 2018 - 2
ITE Journal May 2018 - 3
ITE Journal May 2018 - President’s Message
ITE Journal May 2018 - 5
ITE Journal May 2018 - Director’s Message
ITE Journal May 2018 - 7
ITE Journal May 2018 - People in the Profession
ITE Journal May 2018 - 9
ITE Journal May 2018 - 10
ITE Journal May 2018 - ITE News
ITE Journal May 2018 - ITE, FHWA, and Carmanah Rally to Keep Rectangular Rapid-Flashing Beacons in Our Safety Toolbox
ITE Journal May 2018 - Improving Arterial Roads to Support Public Health: How Can We Do This?
ITE Journal May 2018 - 14
ITE Journal May 2018 - 15
ITE Journal May 2018 - 16
ITE Journal May 2018 - ITE’s Transportation and Health Initiative
ITE Journal May 2018 - 18
ITE Journal May 2018 - Technical Programs Division Spotlight
ITE Journal May 2018 - Industry News
ITE Journal May 2018 - 21
ITE Journal May 2018 - Where in the World?
ITE Journal May 2018 - 23
ITE Journal May 2018 - 24
ITE Journal May 2018 - 25
ITE Journal May 2018 - 26
ITE Journal May 2018 - Member to Member: Jing Zhang, AICP, PTP, LEED AP ND
ITE Journal May 2018 - 28
ITE Journal May 2018 - Countermeasures Prove Effective in Reducing Bicycle Collisions
ITE Journal May 2018 - 30
ITE Journal May 2018 - 31
ITE Journal May 2018 - 32
ITE Journal May 2018 - 33
ITE Journal May 2018 - 34
ITE Journal May 2018 - Guidance on Signal Control Strategies for Pedestrians to Improve Walkability
ITE Journal May 2018 - 36
ITE Journal May 2018 - 37
ITE Journal May 2018 - 38
ITE Journal May 2018 - 39
ITE Journal May 2018 - Factors Affecting Vehicle Passing Distance and Encroachments While Overtaking Cyclists
ITE Journal May 2018 - 41
ITE Journal May 2018 - 42
ITE Journal May 2018 - 43
ITE Journal May 2018 - 44
ITE Journal May 2018 - 45
ITE Journal May 2018 - Measuring the Success of Modal Shift: The Impact on Last Mile Connectivity
ITE Journal May 2018 - 47
ITE Journal May 2018 - 48
ITE Journal May 2018 - 49
ITE Journal May 2018 - Professional Services Directory
ITE Journal May 2018 - 51
ITE Journal May 2018 - 52
https://www.nxtbook.com/ygsreprints/ITE/ITE_July2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_June2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_May2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_April2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_March2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_February2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_January2020
https://www.nxtbook.com/ygsreprints/ITE/ITE_December2019
https://www.nxtbook.com/ygsreprints/ITE/G110939_ITE_November2019
https://www.nxtbook.com/ygsreprints/ITE/G110110_ITE_October2019
https://www.nxtbook.com/ygsreprints/ITE/G110109_ITE_September2019
https://www.nxtbook.com/ygsreprints/ITE/G108559_ITE_August2019
https://www.nxtbook.com/ygsreprints/ITE/G108250_ITE_July2019
https://www.nxtbook.com/ygsreprints/ITE/G107225_ITE_June2019
https://www.nxtbook.com/ygsreprints/ITE/G104039_ITE_May2019
https://www.nxtbook.com/ygsreprints/ITE/G104038_ITE_April2019
https://www.nxtbook.com/ygsreprints/ITE/G104036_ITE_March2019
https://www.nxtbook.com/ygsreprints/ITE/G103582_ITE_February2019
https://www.nxtbook.com/ygsreprints/ITE/G102868_ITE_January2019
https://www.nxtbook.com/ygsreprints/ITE/G100155_ITE_December2018
https://www.nxtbook.com/ygsreprints/ITE/G100154_ITE_November2018
https://www.nxtbook.com/ygsreprints/ITE/G99495_ITE_October2018
https://www.nxtbook.com/ygsreprints/ITE/G98028_ITE_September2018
https://www.nxtbook.com/ygsreprints/ITE/G97366_ITE_August2018
https://www.nxtbook.com/ygsreprints/ITE/G96287_ITE_July2018
https://www.nxtbook.com/ygsreprints/ITE/G94315_ITE_June2018
https://www.nxtbook.com/ygsreprints/ITE/G93877_ITE_May2018
https://www.nxtbook.com/ygsreprints/ITE/G93065_ITE_Apr2018
https://www.nxtbook.com/ygsreprints/ITE/G91484_ITE_Mar2018
https://www.nxtbook.com/ygsreprints/ITE/G89434_ITE_Feb2018
https://www.nxtbook.com/ygsreprints/ITE/G86608_ITE_Jan2018
https://www.nxtbookmedia.com