HCM for Signalized Intersections

Automatic Optimization

A single intersection can be automatically optimized, by selecting the toggle Automatic Optimization (see section Automatic Local Optimization for a Single Intersection)

Create Default Signalization

Set signal group numbers and create sequence. Optimize Cycle Time, Maximum Green and Splits if there is no signalization yet, optimize splits if there already was signalization.

Optimize Splits and Cycle Time

Optimizes local splits and cycle time for current selected intersection

Optimize Split

Optimizes local splits only (maintains cycle time) for current selected intersection

Signal Groups

Insert, Delete and Edit Signal Groups. Inserted signal groups get a correct relation between Minimum Green, Maximum Green, and Split. Default split = Minimum Green + Amber + All Red + Delayed Vehicle Green. The Maximum Green is equal to Minimum Green (see section Global Settings).

Patterns

Insert or delete Patterns. You can select the desired pattern for the current intersection from the Active pattern list field in the Intersection settings area.

Centracs Export

Export the signal controller data of the current intersection to Econolite Centracs^® as a *.csv file.

Priority Scheme

Major flow or minor flow

Analyze Intersection?

A check box indicates this intersection will be included in the analysis and reports.

Analysis Period

Time period for the analysis, either 15 min, utilizing the peak 15-min flow multiplied by 4 assigned by the PHF, or 1 hr, ignoring the PHF.

Located in CBD

A check box indicates the intersection is in a central business district. When active sets the area type (saturation flow) adjustment factor to 0.90. See HCM for description of CBD area.

Controller ID

Each signal controller has a unique ID number. This value defaults to the intersection number, and can be changed for intersections that are controlled by a controller common to another intersection.

To edit default Controllers IDs to another number or specialized agency number systems open the Edit Controller window under Signal Controller ->Edit Controllers. This window allows for editing traffic signal controller IDs and provide a description. This shows the intersection and coordination groups assigned to the controller.

Signal Coordination Group

Signalized intersections of the same sub group are coordinated collectively. Multiple sub groups (coordinated routes) are permitted.

Cycle Length

Controller cycle length. This is the maximum time it will take for each signal group to cycle once. The cycle length is only used for coordination.

S

Active Pattern

• Free Running: The traffic signal controller does not have a set cycle length and is running with fully actuated detection.
• The selected pattern, if various patterns are defined in the Patterns window. You can open the Patterns window via the button Patterns.

Coordination Type

Defines coordination as Time of Day Pattern Coordinated, or Time of Day Pattern Isolated. Value option depends on the Active Pattern value chosen.

The following describes coordination methods:

• Time-of-day Coordinated sets a cycle length and places the controller in coordination with other signals in the same coordination group.
• Time-of-day isolated sets a cycle length but does not place the controller in coordination with other signals.

Actuation Type

Defines whether the controller operates as:

• Fixed time (pre-time) control consists of predetermined signal timing values not based on detection
• Fully actuated: If the Coordination Type is not Free Running, the fixed time signal plan is used to calculate the Force-Off Points of the non-coordinated phases. The user has to provide a valid and useful fixed time signal plan. By modifying the signal plan, the user can influence the calculated Force-Off Points with maximum and minimum green inputs, recalls, and vehicle extensions. This control type sets detection on all lanes that influences signal operations.
• Semi-actuated: contains some lanes with detection that influences signal operations. Often, the major-street thru lanes do not operate with detection to generate phase calls.

Offset

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

S

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). Further explanations can be found in NCHRP Report 812 – Signal Timing Manual. The selections are:

• Lead Green – Beginning of First Green: 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).
• Beginning of Both Green
• Beginning of First Yellow
• Beginning of First Red
• Beginning of First Flashing Don’t Walk

• LagFO (Lagging Force-Off) – The reference point will be at the force-off point for the lagging coordinated signal group.

• LagEnd (End of Lagging Red) – The reference point will be at the end of Red Clear for the lagging coordinated signal group.

• CoordEnd (End of Coordinated Group Red) – 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

Figure 11: Coordination Offset Reference Modes

Permissive Mode

This setting defines the permissive mode for the coordination pattern.

The permissive mode 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 areas follows:

• SingleBand: 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).

• MultiBand: The permissive period for non-coordinated signal groups will open:

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).

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

• Reservice: The permissive mode will operate the same as Single Band Permissive until the coordinated signal groups yield to a non-coordinated movement. ALL signal groups will be allowed to reserve. After the coordinated signal groups yield once:

Permissive Mode

(continued)

• Signal Groups in the non-coordinated barrier group will be allowed to reserve if there is enough time to serve the minimum green time (or minimum permissive green time if greater than minimum green time) and still be able to have the leading coordinated signal group green by the start of its split:

• Signal Groups in the coordinated barrier group will be allowed to reserve if there is enough time to serve the minimum green time (or minimum permissive green time if greater than minimum green time) and still be able to have the coordinated signal group in the same ring green by the start of its split.

Figure 12: Permissive Modes Coordination

Lost Time

Total time per cycle not effectively being used due to driver reaction time, acceleration, and deceleration at the start and end of active signal groups. This is typically three to four seconds per signal group, times the number of signal groups.

S

Pedestrian Walking Speed

Control Type

Defines control of movements as:

• permissive
• protected
• protected / permissive
• split
• overlap
• unsignalized (outer turns only using HCM since 6^th Edition)

Control Type for each movement should be reviewed under the Phasing & Timing section and set to the following:

Permissive (Permitted) control requires motorists to choose acceptable gaps and/or yield to conflicting vehicles or pedestrian traffic streams.

• Protected control assigns the right-of-way to turning drivers.
• Protected/permissive control has a protected signal group assigning right-of-way to turning drivers that then transitions to the permissive parent signal group, requiring turning vehicles to yield.

Note: Permissive/protected control is modeled by selecting protected/permissive and changing the Lead/Lag setting to Lags.

• Split phasing control provides separation between signal groups within the same barrier and prohibits the signal groups from running concurrently.
• Overlap control is a controller output that combines two or more non-conflicting signal groups. This is mostly used to combine signal groups that sit in separate barriers. A common example is when a right-turn movement has an overlap phase running concurrently with the shadowing left-turn movement on the cross-street.

Note: Overlaps can be set for all movements to create advanced signal group combinations like those seen in tight diamond interchanges.

Allow Lead/Lag Optimization

Checkbox to allow for lead/lag optimization

Signal Group

The signal group is the signal phase number

Auxiliary Signal Groups

All signal groups serving the movement. When the Control Type is Overlap and the Signal Group for the Overlap phase is entered, the Auxiliary Signal Groups cell is active and allows selections of any phases with which this movement overlaps.

Note: Overlaps can be set for all movements to create advanced signal group combinations like those seen in tight diamond interchanges.

Lead/Lag

Selection for Lead or Lag left turn for protected phasing

Minimum Green

Minimum green time that the signal group will serve before changing to yellow. Different default Minimum Greens can be set for left and through movements in the Global Settings

Maximum Green

Maximum 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. This parameter when exported to RBC is reflected as Max1. Editing the Split, Amber, All red, or Delayed Vehicle Green the Maximum Green time is automatically adapted, if the signal group satisfies the consistency conditions in all patterns. This implies that the Split is the same in all patterns.

S

Amber

Time a signal group will time an amber interval before advancing to red

S

All red

Time a signal group will time red before a conflicting signal group will be allowed to begin timing

S

Split

Amount of time allocated in the cycle for each signal group to time. The split includes the time it will take the green, yellow, and red intervals to time for each signal group. The split should at least accommodate the signal group Min Green plus Yellow Clearance plus Red Clearance time, but it does not necessarily need to accommodate the full pedestrian service time for an actuated pedestrian signal group. The sum of the splits of all signal groups in each ring should add up to the Cycle Length.

S

Vehicle Extension

Allowed time between successful vehicle extensions before a signal group will gap out. This parameter may be referred to as passage in some controllers and does not affect the capacity calculation.

S

Walk

Minimum time a signal group will display a walk indication before advancing to the pedestrian clearance interval (flashing don’t walk). A signal group may not advance to yellow while the pedestrian movement is in the walk interval.

S

Pedestrian Clearance

Time a signal group will display a flashing don’t walk indication before advancing to solid don’t walk. A signal group may not advance to Yellow while the pedestrian movement is in the pedestrian clearance interval.

Pedestrian clearance is estimated based on lane withs and median widths when Create Default Signalization is clicked.

Note: This is an estimated crossing time and engineering judgment should be used to calculate field-based pedestrian clearance intervals.

S

Delayed Vehicle Green

Delayed Vehicle Green can be used to establish Lead Pedestrian Intervals. This value is the amount of time that the vehicle green interval is delayed before Start of Green. This value allows the pedestrian walk interval to start before vehicle green.

Rest in Walk

l₁, Start-Up Lost Time

Additional time needed to react to the initiation of the green signal and then accelerate

S

l₂, Clearance Lost Time

Time between signal indication changes during which the intersection is not used by vehicles

S

Coordinated

Identifies the coordinate signal groups for the signal controller

Minimum Recall

Signal groups flagged for this option will receive an automatic vehicle call regardless of actuation and time for at least its minimum green time. The green time may extend beyond the minimum if demand is present.

Maximum 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. Normally, the maximum green timer will only time if there are opposing calls to the signal group.

Pedestrian Recall

(Pedestrian push-button)

Signal groups flagged for this option will receive an automatic pedestrian call and time for the full walk plus pedestrian clearance time.

Note: This box does not need to be checked with fixed time signals to recall pedestrians, as this is automatically assumed. For non-fixed time signals, if this box is not checked and crosswalks are present, PTV Vistro will automatically assume that this intersection has a pedestrian push button or pedestrian detector to activate a pedestrian call.

Dual Entry

When a signal group has a call in the next barrier group, concurrent phases in that barrier group may not have a call. In such case both the signal group with the call and the signal group with no call will begin timing when the barrier is crossed if both signal groups are flagged with Dual Entry. This feature is often used for through movement signal groups such that if one signal group is called, the signal group in the opposite direction will automatically serve, even if it does not have a call.

S

Detector

Checkbox to choose detector

Detector Location

Distance upstream of stop bar of leading edge of detector

ft / m

Detector Length

Length of detector

ft / m

Advanced Detector

Checkbox to add a second detector to each movement: Choose the advanced detector

Advanced Detector Location

Distance upstream of stop bar of leading edge of advanced detector

ft / m

Advanced Detector Length

Length of advanced detector

ft / m

I, Upstream Filtering Factor

Adjustment factor to account for the effect of an upstream signal on vehicle arrivals to the subject movement group. This is currently user-defined.

Pedestrian Signal Group

The signal phase number for the exclusive pedestrian phase

Pedestrian Walk

Minimum time the exclusive pedestrian signal group will display a walk indication before advancing to the pedestrian clearance interval (flashing don’t walk). A signal group may not advance to yellow while the pedestrian movement is in the walk interval.

S

Pedestrian Clearance

Time the exclusive pedestrian signal group will display a flashing don’t walk indication before advancing to solid don’t walk. A signal group may not advance to Yellow while the pedestrian movement is in the pedestrian clearance interval.

S

Lane Group

Lane or group of lanes designated for analysis

Control Type

Defines control of movements as:

• permissive
• protected
• protected / permissive
• split
• overlap

C, Cycle Length

Controller cycle length. This is the maximum time it will take for each signal group to cycle once. The cycle length is only used for coordination.

s

L, Total Loss Time per Cycle

Total lost time per cycle for specified lane group

s

l1, Start Up Loss Time

Time consumed to react and begin acceleration after signal group initiates green. Default = 2.0 s

s

l2, Clearance Loss Time

Time consumed at the end of a signal group not serving traffic due to drivers decelerating and stopping in reaction to an amber indication. Default = 3.0 s

s

Green Time Start

Start of the signal group green time in the local cycle

s

Green Time End

End of the signal group green time in the local cycle

s

G, Actual Green Time

Displayed green time per cycle

s

g_i, Effective Green Time

Amount of green time where vehicles proceed at the saturation flow rate

s

g/C, Green / Cycle

The ratio of the effective green time of a signal group to the cycle length

s

(v/s)_i, Volume / Saturation Flow Rate

The ratio of the volume to the saturation flow rate for the specified lane group

veh/h

Critical Lane Group

Lane groups with the highest flow rate are indicated as critical

Lane Group

Lane or group of lanes designated for analysis

Control Type

Defines control of movements as:

• permissive
• protected
• protected / permissive
• split
• overlap

so, Base Saturation Flow Rate

Saturation flow rate for base (ideal) conditions Default = 1900 veh/h/ln

pc/h/ln

Override Base Saturation Flow Rate per lane

Checkbox to activate user input for Base Saturation Flow Rate

N, Number of Lanes

Number of lanes in the lane group

f_w, Lane Width Adjustment

Factor for lane width adjustment

f_HV, HGV Adjustment

Adjustment factor for heavy vehicles

f_g, Grade Adjustment

Adjustment factor for the approach grade

f_HVg, HV and Grade Adjustment

Adjustment factor for heavy vehicles and grade (HCM since 6^th Edition)

f_p, Parking Adjustment

Adjustment factor for parking operations adjacent to travel lane

f_bb, Bus Blocking Adjustment

Adjustment factor for bus periodically blocking travel lane at transit stop

f_a, Area Type Adjustment

Adjustment factor for CBD designation

f_LU, Lane Utilization Adjustment

Adjustment factor for non-balanced lane utilization

Override Calculated Lane Utilization Adj

Checkbox to activate user input for Lane Utilization Adjustment Factor

f_LU,u, User-defined Lane Utilization Adjustment

User-defined Lane Utilization Adjustment Factor. When this is defined, this value will be used in place of the calculated f_LU.

p_LT, Proportion Left Turns

Proportion of left-turning vehicles in the lane

%

p_RT, Proportion Right Turns

Proportion of right-turning vehicles in the lane

%

f_LT, Left Turn Adjustment

Adjustment factor to reflect left-turn geometry

f_RT, Right Turn Adjustment

Adjustment factor to reflect right-turn geometry

f_Lpb, Left Turn Pedestrian Adjustment

Pedestrian adjustment factor for left-turn groups

f_Rpb, Right Turn Pedestrian Adjustment

Pedestrian adjustment factor for right-turn groups

f_CAV, prot

CAV protected left turn adjustment. Only relevant for lane groups, that have an inner turn and if the respective phase exists in the signal timing, (HCM 7^th Edition)

f_CAV, perm

CAV permissive left turn adjustment. Only relevant for lane groups, that have an inner turn and if the respective phase exists in the signal timing, (HCM 7^th Edition)

Is Workzone in Approach

Checkbox to activate if a workzone is present on the approach (HCM since 6^th Edition)

Number of open lanes in Workzone

Number of open lanes in the workzone (HCM since 6^th Edition)

Total lane width in Workzone

Total width of all open lanes on the approach in the workzone (HCM since 6^th Edition)

ft / m

fwz, Work Zone Adjustment

Adjustment factor for work zone presence (HCM since 6^th Edition)

fsp, Sustained Spillback Adjustment

Adjustment factor for effect of spillback from the downstream intersection (HCM since 6^th Edition)

fms, Downstream Lane Blockage Adjustment

Adjustment factor for downstream lane closure (HCM since 6^th Edition)

s, Calculated Final Saturation Flow Rate

Calculated final saturation flow rate after all adjustments has been taken into account.

veh/h/ln

Override Calculated Saturation Flow Rate

Checkbox to activate user input for Saturation Flow Rate

User-Defined Saturation Flow Rate

User-defined Saturation Flow Rate. When this is defined, this value will be used in place of the Calculated Final Saturation Flow Rate.

veh/h/ln

Arrival Type

The arrival type selects the Platoon Ratio which describes the level of platooning quality arriving at the selected approach. The platoon ratio will be automatically updated based on the selection of Arrival Type per approach.

Default = 3. Range = 1 – 6 (very poor – exceptional coordination):

1 Very Poor Progression

2 Unfavorable Progression

3 Random Arrivals or Uncoordinated (default)

4 Favorable Progression

5 Highly Favorable Progression

6 Exceptionally Favorable Progression

The Arrival Type should be updated to match the field or desired conditions. See the HCM for further guidance on selection of the Arrival Type and Platoon Ratio.

Lane Group

Lane or group of lanes designated for analysis

Control Type

Defines control of movements as:

• permissive
• protected
• protected / permissive
• split
• overlap

V, Volume

Lane group volume (total analysis volume)

veh/h

s, Saturation Flow Rate

Final saturated flow rate (calculated or user-defined)

veh/h

c, Capacity

Effective capacity, taking into account all opposing flows etc.

veh/h

g/C, Green / Cycle

The ratio of the effective green time of a signal group to the cycle length

X, Volume / Capacity

The ratio of the total analysis volume (flow rate) to the capacity

d1, Uniform Delay

The first term of the equation for lane group control delay, assuming constant arrival and departure rates during a given time period.

s

k, incremental delay calibration factor

Incremental delay factor used to account for the effect of controller type on delay. Default = 0.50

d2, Incremental Delay,

The second term of lane group control delay, accounting for delay due to the effect of random, cycle-by-cycle fluctuations in demand that occasionally exceed capacity (i.e., cycle failure) and delay due to sustained oversaturation during the analysis period.

s

d3, Initial Queue Delay

The third term of lane group control delay, accounting for delay due to a residual queue identified in a previous analysis period and persisting at the start of the current analysis period. This delay results from the additional time required to clear the initial queue.

s

Rp, Platoon Ratio

Describes the quality of signal progression for the corresponding movement group. Values based on HCM look-up table for arrival type.

P, Proportion Arriving on Green

Proportion of vehicles arriving during the green indication

%

PF, Progression Factor

Delay adjustment factor based on the progression quality

X, Volume/Capacity for Lane Group

The ratio of the total analysis volume (flow rate) to the capacity

d, Delay for Lane Group

Control delay for lane group

s/veh

Lane Group LOS

Level-of-service for lane group

Critical Lane Group

Lane groups with the highest flow rate are indicated as critical.

50th-Percentile Queue Length

50^th percentile queue length measured in number of vehicles per lane

veh

50th-Percentile Queue Length

50^th percentile queue length measured in feet per lane

ft

95th-Percentile Queue Length

95^th percentile queue length measured in number of vehicles per lane

veh

95th-Percentile Queue Length

95^th percentile queue length measured in feet per lane

ft

d_M, Delay for Movement

Control delay per movement

s/veh

Movement LOS

Level-of-service for movement

Critical Movement

d_A, Approach Delay

Average control delay by approach

s/veh

Approach LOS

Level-of-service for approach

d_I, Intersection Delay

Average control delay for intersection

s/veh

Intersection LOS

Level-of-service for intersection

Intersection V/C

Volume-to-capacity ratio for the intersection

g_Walk,mi, Effective Walk Time

Effective walk time for the phase serving the minor street movement

s

M_corner, Corner Circulation Area

Corner circulation area per pedestrian. The subject corner is the near-side corner on the subject approach on the side of the direction of travel (e.g., right side for right-hand traffic, left side for left-hand traffic).

ft²/ped

m²/ped

M_CW, Crosswalk Circulation Area

Crosswalk circulation area per pedestrian

ft²/ped

m²/ped

d_p, Pedestrian Delay

Pedestrian delay while waiting to cross the street

I_p,int, Pedestrian LOS Score for Intersection

Pedestrian LOS score

Crosswalk LOS

Pedestrian LOS based on pedestrian LOS score

c_b, Capacity of the bicycle lane

Capacity of the bicycle lane

d_b, Bicycle Delay

Bicycle delay

I_b,int, Bicycle LOS Score for Intersection

Bicycle LOS score

Bicycle LOS

Bicycle LOS based on bicycle LOS score

Ring 1

User defines the Signal Groups that occur on Ring 1

Ring 2

User defines the Signal Groups that occur on Ring 2, if applicable

Ring 3

User defines the Signal Groups that occur on Ring 3, if applicable

Ring 4

User defines the Signal Groups that occur on Ring 4, if applicable