synchrosimtraffic handout

Institute of Transportation Engineers, Purdue Student Chapter engineering.purdue.edu/ITE

Synchro & SimTraffic

Using Synchro and SimTraffic in

Traffic Analysis

October 28, 2010 Md. Shafiul Azam

Contents

PART A- BASIC SIGNAL TIMING CONCEPTS ................................................................................... 2

Signal Timing Objective ........................................................................................................................ 2

Traffic Signal Policy ............................................................................................................................... 2

Basic Operational Principles ................................................................................................................. 4

Methods of Signalized Intersection Analysis (STM, FHWA) .......................................................... 5

Basic Performance Measures ................................................................................................................ 5

Types of Traffic Signal Control ............................................................................................................ 6

Basic Traffic Signal Parameters ............................................................................................................ 7

Actuated Timing Parameters .............................................................................................................. 10

PART B- GETTING FAMILIAR WITH SYNCHRO & SIMTRAFFIC ............................................... 14

Basic Features of Synchro.................................................................................................................... 14

Utilities and Toolbars of Synchro ...................................................................................................... 14

Lane Window ....................................................................................................................................... 16

Timing Window ................................................................................................................................... 20

Phasing Window .................................................................................................................................. 25

Time-Space Diagram Window ........................................................................................................... 26

Introduction to SimTraffic ...................................................................................................................... 27

Measures of effectiveness in SimTraffic ............................................................................................ 27

SimTraffic Parameters ......................................................................................................................... 27

Simulation Control ............................................................................................................................... 28

Instantaneous Status ............................................................................................................................ 28

SimTraffic Reports ............................................................................................................................... 29

PART C- EXAMPLE EXERCISES .......................................................................................................... 31

Exercise 1: Isolated Intersection with Pre-timed Controller .......................................................... 31

Exercise 2: Isolated Intersection with Actuated Controller ............................................................ 34

Exercise 3: Closely Spaced Intersection with Single Controller .................................................... 39

Exercise 4: Fixed Cycle Coordination ................................................................................................ 42

Institute of Transportation Engineers, Purdue Student Chapter


PART A- BASIC SIGN

Signal Timing Objective

-Assign the right-of-way to alternating traffic movements in such a way that it minimizes the

average delay to any group of vehicles or pedestrians as well as reduce the probability of

accidents involving conflicting traffic.

-Traffic signal can be implemented for an isolated intersection; however, the objective of signal

timing is to optimize corridor or network performance by reducing delays.

Traffic Signal Policy

Signal Timing affects quality of transpo

community matters. Signal timing environment has two major components:

policy and process. Signal timing process itself nests within

Signal Timing Policy

A cyclic process which can be updated based on road users’ feedback.

Examples

• Regional Transportation Policy

Multimodal Transport,

Signal Timing

Process

Operation

and

Maintainance


BASIC SIGNAL TIMING CONCEPTS

way to alternating traffic movements in such a way that it minimizes the


conflicting traffic.

Traffic signal can be implemented for an isolated intersection; however, the objective of signal

timing is to optimize corridor or network performance by reducing delays.

Signal Timing affects quality of transportation system which in turn affects almost all

Signal timing environment has two major components: Signal Timing

policy and process. Signal timing process itself nests within the policy paradigm.

hich can be updated based on road users’ feedback.

Figure 1 Signal Timing Policy Cycle

Regional Transportation Policy: Green Transportation, Low Cost Signal (e.g. pre

Regional

Transportatio

n Policy

Signal Timing

Policies

Location

Consideratio

n

Signal Timing

Process

engineering.purdue.edu/ITE

way to alternating traffic movements in such a way that it minimizes the


Traffic signal can be implemented for an isolated intersection; however, the objective of signal

rtation system which in turn affects almost all

Signal Timing

policy paradigm.

: Green Transportation, Low Cost Signal (e.g. pre-timed),



• Signal Timing Policies: Pedestrian/bicyclist focus, Selection of measures of effectiveness,

Priorities to different roadway class, choice of coordinated control

vehicle focused

• Local Considerations: City Plans. Signals at driveway, signal at high pedestr

area (e.g. Stadium and Northwestern needed an exclusive pedestrian phase)

• Signal Timing Process: see below

• Operation and Maintenance:

years, periodic updating (e.g. change in minimum split, pedestrian clearance or vehicle

extension time), repair detectors

Signal Timing Process

Roles of Synchro and SimTraffic in Signal Timing Process

• Model Development- Model

configuration, traffic volume

• Performance Measure: use appropriate performance

stops, LOS, fuel consumption etc.

• Timing Evaluation: Evaluating

in SimTraffic

• Assessment: Based on the field evaluation

assessed and proper documentation can be prepared

Project Scoping

Data Collection

Model Developme

nt


Pedestrian/bicyclist focus, Selection of measures of effectiveness,

Priorities to different roadway class, choice of coordinated control, Transit or emergency

City Plans. Signals at driveway, signal at high pedestr


see below

Operation and Maintenance: feedback from road users, overall performance for next few


extension time), repair detectors

Figure 2 Signal Timing Process

in Signal Timing Process

Model the street network in Synchro with appropriate lane

traffic volume, signal timing and phasing

: use appropriate performance measure, i.e. delay, number or

stops, LOS, fuel consumption etc.

: Evaluating signal timing under various scenarios or simulate them

: Based on the field evaluation any modification in timing plan can be

proper documentation can be prepared in Synchro and SimTraffic

Model Developme

Implement and Fine Tuning

Timing Evaluation

Perfromance Measure Evaluation

Synchro

SimTraffic

role


Pedestrian/bicyclist focus, Selection of measures of effectiveness,

, Transit or emergency

City Plans. Signals at driveway, signal at high pedestrian crossing


feedback from road users, overall performance for next few


street network in Synchro with appropriate lane

i.e. delay, number or

signal timing under various scenarios or simulate them

ion in timing plan can be

in Synchro and SimTraffic

Policy Evaluation

Assessment

Synchro &

SimTraffic can play

role



Basic Operational Principles

Figure 3 Typical Flow for Signalized Movement (STM, 2008)

• When vehicles start moving from a stopped condition they have a saturation flow rate

which dissipates over time.

• There is a ‘start-up lost time’ during which there is no vehicle movement.

• There is a certain period of time during yellow interval during which vehicles get

cleared off from the intersection. After that there is no traffic flow for the rest of the time

yellow or AR period, which is known as ‘clearance lost time’.

• Deducting the lost time (start-up and clearance) from green interval provides the

‘effective green time’

• Capacity for a particular movement at a signalized intersection can be computed as:

Capacity, C= Saturation flow *effective green time /Cycle Length.

• ‘Volume to Capacity ratio’ can be simply calculated once we have the capacity.

Critical flow movement

The conflicting traffic need to share time of a particular cycle length based on the critical

movement analysis. This is the fundamental and simplest operational principle for any

traffic signal.

1 Critical flow

Movement Design Flow

Rate Saturation Flow Rate

Flow Ratio

Northbound L 600 pcu/hr 1200 pcu/hr 0.51

Northbound TR 500 pcu/hr 1700 pcu/hr 0.294

Southbound L 450 pcu/hr 1330 pcu/hr 0.338

Southbound TR 720 pcu/hr 1600 pcu/hr 0.45



Methods of Signalized Intersection Analysis (STM,

Basic Performance Measures

Control Delay & LOS

• The component of delay that results when a control signal causes a lane group to reduce

speed or to stop; it is measured by comparison with the uncontrolled condition.

• HCM chapter 16 provides detailed

are lane group volume and capacity, cycle length, and effective green time.

• For each movement there is respective control delay, when we average that across all

movements weighted by volume we obtain i

• Level of service for a signalized intersection is based on the control delay at signalized

intersections. The LOS can be expresses for individual movement, approach or for

intersection as a whole.

• LOS for other control type (unsignalized

Queue Length

• This is the measure of physical space vehicles occupy while waiting to proceed through

an intersection

Quick Estimation Method

HCM Operational Procedure

Arterial and Network Timing Models

Microsopic Simulation Models


Methods of Signalized Intersection Analysis (STM, FHWA)

Basic Performance Measures

The component of delay that results when a control signal causes a lane group to reduce


HCM chapter 16 provides detailed equations for calculating control delay. Some factors


For each movement there is respective control delay, when we average that across all

movements weighted by volume we obtain intersection delay.

Level of service for a signalized intersection is based on the control delay at signalized


LOS for other control type (unsignalized intersection) have different ranges

This is the measure of physical space vehicles occupy while waiting to proceed through

•Start with Critical Movement Analysis

•Generate Initial Signal Timing Plan

•Can't be used for detailed analysis

•More detailed analysis with additional data

•Performance analysis by lane group

•Adopted as a standard by many public agencies

•Each vehicle is propagated through sthe system as a separate entity and

updated typically once per second

•Queue blocking and overflow effects are recognized

•Each vehicle is treated indovidually as opposed to aggregatedby lane group

Arterial and Network Timing Models

•Time-Space relationship between individual signals is investigated

•Macrosopic propagation of traffic through the syntem

•Optimal signal timing plans are produced


The component of delay that results when a control signal causes a lane group to reduce


equations for calculating control delay. Some factors


For each movement there is respective control delay, when we average that across all

Level of service for a signalized intersection is based on the control delay at signalized


intersection) have different ranges

This is the measure of physical space vehicles occupy while waiting to proceed through

Each vehicle is propagated through sthe system as a separate entity and

Queue blocking and overflow effects are recognized

Each vehicle is treated indovidually as opposed to aggregatedby lane group

Space relationship between individual signals is investigated

Macrosopic propagation of traffic through the syntem



Types of Traffic Signal Control

Traffic signal can operate either in pre-timed or actuated more or combination of two.

Pre-timed Signal Control Timing is decided based on predetermined demand and usually remained fixed. Signal timing may be different during peak and off-peak hours. Example: Peak: 8-12 & 4-8 pm Off peak: 9 pm to 7 am Midday Peak: 1-3 pm Actuated Signal Control The signal timing and phasing are dictated by the demand of the traffic detected by detectors on the ground or be video detection. Actuated signal can be subdivided into semi actuated and fully actuated signal.

Pre-timed Isolated

Pre-timed Coordinated

Semi Actuated Actuated Un-coordinated

Actuated-Coordinated

Cycle Length

Fixed Fixed Variable Variable Fixed

Conditions to install

Where detection is not available or costly to implement

-Where traffic is consistent -Intersections are closely spaced -consistent cross street

-Major (one movement) is desirable -major road has a posted speed limit of 40 mph or less -cross road carries light traffic demand

-Where detection is provided on all approaches, - isolated locations with a posted speed >40 mph

Arterial with heavy traffic with cross intersections closely spaced

Example Work zones CBD, interchanges

-Highway operations

Locations without nearby signals; rural, high speed locations; intersection of two arterials

Suburban arterial

Benefits Temporary application keeps signals operational

-Predictable operations, -lowest cost of equipment and maintenance

-Lower cost for highway maintenance

Responsive to changing traffic patterns, -efficient green time allocation, reduced delay, improved safety

Lower arterial delay, potential reduction in delay for the system, depending on the settings



Basic Traffic Signal Parameters

Cycle Length

Time required for a complete sequence of signal indications

One approach of determining cycle length is by Webster method:

�� = 1.5� + 51 −

Where,

C0 = the optimal minimum delay cycle length, sec;

L = total lost time within the cycle, sec; and

Y = the sum of critical phase flow ratios

Assumptions of cycle length at planning level

• Permissive left turn – 60 sec

• Protected left turns, protected-permissive left turn s, split phasing on one street- 90 sec

• Protected left turns, protected-permissive left turns , split phasing on both streets- 120 sec

Vehicular Green Interval/Split

Green time interval/split is the segment of cycle length allocated for each phase.

The term phase and interval have different meaning in traffic signal. Interval is a time period

during which the traffic signal indication does not change. For example, a pedestrian phase

contains three intervals—Walk, Flashing Don’t Walk, and solid Don’t Walk—and within the

Walk and Flashing Don’t Walk intervals, the corresponding through movement will remain

green. On the other hand phase in the time period to allocate a specific movement to clear off

the intersection and it also include the yellow and all red intervals.

A green phase usually begins due to actuation or recall and has the following parts: Minimum

green/minimum initial, Vehicle extension, clearance interval: all these should sum up to be

equal to or less than the maximum allowable green time for a phase.



Clearance Interval

Yellow and all red timing are together known as the clearance interval for a phase which is the

transition time from one phase to another. For calculating the clearance interval the following

formula is used:

Y+AR = t+V /(2a ± 64.6*G)+ (w+L)/V Here, t= perception reaction time (typically taken as 1 sec) V= approach speed (ft/sec) a= rate of deceleration (10 ft/sec2) G= approach grade (percentage of grad divided by 100) w= width of intersection in feet L=length of vehicle in ft (normally taken as 20 ft)

Pedestrian Timing Interval- Walk, Pedestrian Clearance (Flashing Don’t Walk)

• The pedestrian timing requirement has two major components

• Walk interval 4-7 seconds which allows pedestrian to leave the curb before the beginning

of flashing don’t walk interval

• Flashing don’t walk interval- provides a pedestrian adequate time to cross the roadway.

This can be calculated as: FDW= W/WS where, W= crossing distance and WS= walking

speed which is normally 3.5-4 ft/sec

Movement and Phasing, Ring and Barrier, Left Turn Phasing

• The MUTCD defines a signal phase as the right-of-way, yellow change, and red clearance

intervals in a cycle that are assigned to an independent traffic movement or combination

of traffic movements.

• The ‘movements’ served at an intersection can be classified d by the various users:

vehicles, pedestrians, bicyclists, and transit. Movements are regulated by the signal

controller through their allocation to one or more signal phases.

Movement

Total 6 movements Two Vehicular (and two pedestrian phases)

Figure 4 Phase and Movement



Ring and Barrier

• Modern signal control organizes phases by grouping them in a continuous loop or ring

and separating the crossing or conflicting traffic streams with time.

• Separation can be achieved either by making the movements sequential or adding a

barrier between the movements.

• Ring identifies phases that may operate one after another and are typically conflicting

phases organized in an order. For instance, traffic traveling through the intersection in

the northbound direction and southbound left turn movements. Clearance time is used

to separate that movement in time.

• The barrier represents a reference point in the cycle at which a phase in each ring has

reached a point of termination; both rings must cross the barrier simultaneously. For

example barrier can be used to separate the east-west movements from north-south

movements.

Figure 5 Phase and Interval Illustration (STM, 2004)

Barrier



Left Turn Phasing Options

• Permissive only left turn operation reduces delay for the intersection, but may affect

intersection safely because motorists have to turn negotiating appropriate gaps

• Protected only left-turn phases may reduce delay for turning vehicles but often increase

overall intersection delay

• Protected-permissive left turn phases can offer a good compromise between safety and

efficiency. However, this can limit available options to maximize signal progression

coordination unless

• Split phasing may be applicable with shared lanes, but could increase coordinated

length if both split phases are provided a concurrent pedestrian phase

• Left turns may need to be prohibited sometimes to reduce conflicts at the intersection

Actuated Timing Parameters

Phase recalls

Racall places a call by default for a specific phase each time the controller is serving a

conflicting phase. There are four types of recall- vehicle recall or minimum recall, maximum

recall, pedestrian recall and soft recall

Recall Type Definition Uses

Minimum Recall Puts call to controller by vehicle itself. Call is cleared after the green phase begins.

Frequently used for major road through movement at semi-actuated non-coordinated phase

Maximum Recall Puts continuous call for maximum amount of green time.

-where fixed time operation desired -when vehicle detection out of service -when gapping out is not desired (e.g. left lagging phase for actuated coordinated control)

Pedestrian Recall Puts continuous call for pedestrian service on the phase

-high pedestrian demand (e.g. Purdue campus) -when pedestrian detection is out of service

Soft Recall In absence of serviceable conflicting call puts a continuation call for present phase

-major road through movement in absence of conflicting vehicle presence



Vehicle Extension Time/Unit Extension Time/Passage Time

• Vehicle extension/unit extension/ passage time is used to extend the green interval

based on the detection status when the phase is green.

• Extends the Green Interval for each vehicle actuation up to the Maximum Green

• Begins timing when the vehicle actuation is removed

• This extension period is ends by maximum Green timer or a force off

• When vehicle extension time>minimum gap and there is no conflicting call the scenario

is called “Gap Out”

• Passage time can be determined by using the following equation:

Pt, sec = Max. Allowable headway, sec -(length of vehicle, ft + length of detection zone,

ft)/(1.47* approach speed, mph)

Simultaneous Gap

• When one phase is gap out and there is a barrier associated with another phase

simultaneous gap can cause both to jointly terminate

• Used to provide safe phase termination

Dual Entry

• Dual Entry is used to call vehicle phases that can time simultaneously even if only one

phase is receiving active call.

• One common use of dual entry is to activate the parameter for compatible through

movements.

Volume Density Features- Gap Reduction, variable initial

• Volume density permits variable parameters for vehicle extension and green time.

Maximum Allowable Headway

Vehicle length Det. Length Gap (i.e. speed*Pt)

Figure 6 Vehicle Extension Time Calculation



• The reason behind a variable vehicle extension time is that during first few seconds of

green phase there is some sluggish movement for the vehicles (initial queue) but once

the speed up they move faster and there is a need to reduce the allowable gap out time

• A constant extension time may not differentiate between initial queue and subsequent

random platoon

Variable Initial

• Variable initial is used to ensure that all vehicles queued between stop line and nearest

upstream detector are served.

• Variable initial uses detector activity to determine a minimum green

• When vehicles reach intersection on red detectors advanced detectors detects the

number of vehicles coming and extend the initial green by an amount that that queue

can pass.

Vehicle Extension Time

Minimum Gap

Time before Reduce Time to Reduce

Time

Ex

ten

sio

n T

ime

r Li

mit

s

Actuation of conflicting

movement

Figure 7 Variable Vehicle Extension

Maximum Initial

Minimum Green

Time

Du

rati

on

of

Init

ial

Inte

rva

l

Detctions

Added Initial

Figure 8 Variable Initial Green



Timing and Phasing Window in Synchro for Detailed Inputs

Input for volume-density parameters Input Recall Mode Output Delay Output queue

Input for vehicle extension Input for min/max split, min initial and clearance interval



PART B- GETTING FAMILIAR WITH SYNCHRO & SIMTRAFFIC

Basic Features of Synchro

• Synchro- A software package

• In Synchro capacity analysis

(ICU) method as well as the Highw

• Can be used to optimize

• Can also be used to optimiz

intersections along corridor or network

• Synchro can implement modeling for actuated signal

• It has the capability to represent the

of traffic flows between intersections).

• Time space diagram is important in visualizing the overall performance of the

intersection/group of intersections.

Utilities and Toolbars of Synchro

• Main window of Synchro has the following

Window selection palette has different gateways for setting lane configuration, volume input, timing, phasing. There are optiondatabase and a toolbar to run Si

Map

Window

Toolbar

Palette


GETTING FAMILIAR WITH SYNCHRO & SIMTRAFFIC

A software package for modeling and optimizing signal timings

nalysis is performed based on Intersection Capacity Utilization

(ICU) method as well as the Highway Capacity Manual (HCM) method

the cycle length and splits for isolated intersections

ptimize the cycle length, splits and offsets for a group of

intersections along corridor or network

Synchro can implement modeling for actuated signal using necessary parameters

represent the time-space diagram (i.e. a graphical representation

fic flows between intersections).

Time space diagram is important in visualizing the overall performance of the

intersection/group of intersections.

of Synchro

Main window of Synchro has the following toolbars (See figure below)

has different gateways for setting lane configuration, volume There are options to visualize time-space diagram, connecting to

database and a toolbar to run SimTraffic Animation.

Node #

Window Selection Palette

Selected Intersection

Link Node

Representation

Map


GETTING FAMILIAR WITH SYNCHRO & SIMTRAFFIC

for modeling and optimizing signal timings

based on Intersection Capacity Utilization

intersections

cycle length, splits and offsets for a group of

using necessary parameters

a graphical representation

Time space diagram is important in visualizing the overall performance of the

has different gateways for setting lane configuration, volume space diagram, connecting to

Representation



Left Column

Zoom in

Zoom All

Add Link

Move Node

No Map Info(will remove any

information for node)

Show Cycle Length

Show Coordinability Factor

Show Locked Timings

Show No Arrow (cleaning map except

Road Names)

No Text Movement (same as above w/o moving road names)

Show Start of Green

Show Volume to Capacity (V/C) ratio


Map Window Toolbars

Column Middle Column Right

Zoom in Zoom out Zoom window

Zoom All Zoom Previous Zoom Scale

Add Link Delete Link Link Settings

Move Node Delete Node Transform Map

No Map Info (will remove any

information for node)

Show Int. Delay (will show the overall

intersection delay/vehicle) Show Level of Service

Show Cycle Length Show Natural Cycle Length Intersection Capacity Utilization

Show Coordinability Factor

Show Natural Coordinability Factor Show Node Number

Show Locked Timings Show Intersection Zones Volume Balancing

Show No Arrow (cleaning map except

Road Names) Show Lanes on Map Show Movement in Map

No Text Movement (same as above w/o moving road names)

Show Traffic Volume on Map

Show Link Distance, Speed Travel Time on Map

Start of Green Show Start of Green Time Show Maximum Green Time

Show Volume to Capacity (V/C) ratio Show Movement Delays Show Phase Numbers


Right Column

Zoom window

Zoom Scale

Link Settings

Transform Map

Show Level of Service

Intersection Capacity Utilization

Show Node Number

Volume Balancing

Show Movement in Map

Show Link Distance, Speed Travel Time on Map

Show Maximum Green Time

Show Phase Numbers



Lane Window Input Parameters

Lane and Sharing -shared lanes are considered as thru lane. -exclusive tuning lanes are considered as turning lanes. Ideal Saturation Flow, So -unit is in vehicles per hour per lane . -default value is 1900 veh/hr/lane. Lane Width -12 ft is the default value - for lane group use average lane width. -Lane width factor is calculated by the following formula: FW = 1+(W-3.6)/9, here W is lane width in meter. Grade (in %) -grade for each approach towards intersections. -for uphill +ve value, for downhill –ve value. -based on grade an adjustment factor (FG) is calculated where; FG = 1-%grade/200. Area Type -can be Central Business District or Other -there is an area type adjustment factor, FA (0.9 for CBD and 1 for other areas) Storage Length -number of lanes in the right or left storage bay. -if storage length is zero no ‘blocking analysis’ is performed. Storage Lanes -the number of lanes in the right or left storage bay. -values appear when storage length is greater than zero. Total Lost Time -time lost is seconds due to phase change (default value is 4 sec). -Synchro calculated lost time, tL= start-up lost time + clearance lost time= 2 sec+(yellow plus all red-time – extension of effective green (2 sec)). Leading Detector -distance of the leading edge of the most advanced detector to the stop bar (in feet). -only applicable for actuated signal analysis. Trailing Detector -distance from the trailing edge of the trailing detector to the stop bar (in feet).



Figure 9 Leading and Trailing Detector

Turning Speed -turning speed of the vehicles while vehicle is traveling inside the intersections (only used by SimTraffic during simulation). Right Turn Channelization and its Control -for right turn movement the presence of channelization and it’s control. -when there is no channelization specify “None”. Other controls are yield, stop, merge and signal. Curb Radius -measured from center point to curb and used to control the graphics in SimTraffic. Additional Lanes -additional lanes for right turn movement. For yield or merge the value is zero.

Derived Parameters Lane Utilization Factor, FLU -when there is more than one lane in a lane group, the lanes are not used equally and there is a need to adjust the saturation flow in each lane accordingly. -example: if number of lane is 1, the lane utilization factor for thru, left/right or shared lane is 1. -if number of lane is 2 for thru or shared lane the FLU=0.95 whereas for 2 left lane the value is 0.97 and

for 2 right lane the value is 0.88. FLU =� ��

(# ��∗�� .)

Right Turn Factor, FRT -represents how much the interference from right-turning reduces the saturated flow rate.

-FRT = 1 - 0.85 * PRT -for permitted right turn movements; it is further reduced by conflicting pedestrian Left Turn Factor, FLT (proc & perm) -it represents the reduction of saturation flow rate by inference from left turn traffic FLT=1/(1+1.05*PLT) here; PLT= proportion of left turn in lane group



Right Ped Bike Factor, FRPB -it is calculated based on the number of pedestrian and bicyclist crossing against right turn movement (different from HCM calculation). -Synchro assumes right turns are always permitted (not protected) from a left or thru lane group except for unusually aligned intersections Left Ped Factor, FLPB -it is calculated based on the number of pedestrian and bicyclist crossing against left movement -Synchro calculation is based on permitted phase only. Saturated Flow Rate, S (proc & perm)

S = So * N * FW * FHV * FG * FP * FBB * FA * FLU * FLT * FRT * FLPB * FRPB S = Saturation flow rate for the subject lane group, expressed as a total for all lanes in the lane group, veh/h So = Base saturation flow rate per lane, pc/h/In, N = Number of lanes in the lane group,

Fw, FHV, FG, FP, FBB, FA, FLU, FLT, FRT, FLPB, FRPB are adjustment factors for roadway width, heavy vehicle, grade, parking lane, blocking effect of local buses with intersection area, area type, lane utilization, right turn, ped/bike crossing for left and right movements, respectively

Saturated Flow Rate (RTOR)

-based on the signal timing Synchro automatically calculates the saturation flow rate for RTOR. SRTOR = Minimum (SRTOR1, SRTOR2) SRTOR1 = saturation flow rate based on gaps in merging traffic SRTOR2= blocking limit to saturation flow rate based on through traffic blocking access to stop bar SRTOR1 = å(SRTORi * Ri) / Sum(Ri)

where, SRTORi is the saturation flow rate for time interval i Ri= length of timing interval i SRTOR2 = VR/VNRT * (storage +1) * 3600 / R = blocking limit to saturation flow rate here, VR = right turn volume, VNRT = non right turn volume in lane, storage= length of storage bay in vehicles, R= length of entire red time



Volume Window

Input Parameters Traffic Volume -hourly Traffic Volume for each movement Conflicting ped(#/hr) -hourly conflicting pedestrian for right/left turn movements Conflicting bikes(#/hr) -hourly conflicting biker for right turn. It is assumed that conflicting bikers for left turn will clear during the queue clearance time for vehicles Peak Hour factor -factors calculated based on 15-minute highest count. PHF= 4* 15-minute highest count/flow rate Growth Factor -growth factor is used to adjust volume. An example can be we have 2010 count data and we want to check traffic condition in 2012. -the growth factor is calculated as GF= (1+r)Y, here r= growth rate and Y= number of years Heavy Vehicle (%) -this is the percentage of heavy vehicle in traffic stream. -based on this percentage Heavy Vehicle Adjustment Factor is calculated -FHV= 100/{100+ heavy veh %*(Et-1)}; here, Et= passenger car equivalent factor for heavy vehicle (Synchro uses a default value of 2) Bus Blockages (#/hr) -if any approach is expected to be blocked by buses then number of buses that stop and block traffic per hour should be included here Adjustment factor for bus blockage is calculated by: FBB = [N-(14.4Nb/3600)]/N; here N= number of lane in lane group, Nb = number of bus stopping/h Presence of Parking Lane & Parking Maneuver (veh/hr) -whether or not there is an adjacent parking lane for parallel parking. -Synchro will calculate a parking factor to be multiplied with basic saturation flow as a parking adjustment and the formula to calculate the parking factor is as follows: FP= [N-0.1-(18Nm/3600)]/N; where Nm is the number of parking maneuver per hour Link O-D Volume -it is used to allow detailed control over the origin and destination between two adjacent intersections. Usually needed for short links, multiple intersections controlled by single controller or in the median of a wide arterial



Timing Window

Global Parameter Controller Type -user must specify the controller type: Pre-timed, actuated uncoordinated, actuated coordinated, semi actuated uncoordinated, unsignalized, roundabout Cycle Length -shows current cycle length value Lock Timing -used to lock already decided timing for any individual or group of intersections Offset Settings -used for progressive signal to relate start of green time (also need to specify the reference phase and interval of offset calculation e.g. begin of green, begin of yellow of EB-WB thru) Master intersection -master intersection is the reference for a zone or network of intersection. -for progressive signal offset will be calculated based on master (or reference intersections)

Input Parameters Lanes and Sharing& Traffic Volume Obtained from lane window input Turn Type -turn Type is used to set setting for left turn or right turn treatments -can be permitted, protected, permitted-protected, split, Dallas permitted (plus protected) and custom type. If NA is selected left/right turn is meant ‘prohibited’.

Derived Parameters

Adjusted Flow - Volume*PHF*GF Lane Group Flow -assigned traffic flow to lane groups. -for shared turning lane the turning volume is assigned to the through lane group. For exclusive turning lane the turning volumes are kept separate from thru volume.



Protected/permitted Phases -used to assigned one or more phase to movements. Detector Phase Detectors in the subject lane group call and extend the Detector Phases. The Detector Phases are set to be the Protected Phases, or the Permitted Phases if no Protected Phase exist. Calls on this lane group will call and extend phases listed in the detector phase setting. Example 1 (isolated)

-Here, there are 10 different movement based on lane configuration and eight different phases considering protected phase for left turning.

Protected only

-Since there is high left turn volume from main street (dual left turn lane for EBL and WBL) a protected phase is desired. Therefore, we will select turn type as protected. -Protected left turn is also provided for NB/SB left turns

Protected+Permissive

-if NBL and SBL is protected+permissive then phase 8 and 4 will also be assigend to NBL and SBL permisive phases, respectively.

Example 2 (closely spaced)

-Two closely spaced intersections. -Will be controlledby one cotroller and dual ring. -Ring 1 for east intersection and ring 2 for west intersection.



Intersection 1

Phasing:

East Intersection Three phases:ø1, ø 2 and ø 4 will accommodate five movements. EBT&R: ø 2 (protected) WBT: ø 2 & ø 1 (protected) WBL: ø 1 (protected), ø 1 , ø2 (permissive) NBL: ø 4 (protected) NBR: ø 4 (permissive), ø 1 (protected)

Intersection 2

Phasing:

West Intersection Three phases:ø5, ø 6 and ø 8 will accommodate six movements. EBT: ø 6 & ø 5 (protected) EBL: ø 5 (protected) : ø 5, ø 6 (permissive) WBT&R: ø 6 (protected) SBL: ø 8 (protected) SBR: ø 8 (permissive), ø 5 (protected)

Minimum Initial -place the minimum initial green for a phase. -a typical value of 4 sec is usually use. -allowable range in Synchro 1-840 sec. -also known as minimum green. Minimum Split -shortest amount of time allowed for a phase. -should be at lease minimum initial+ clearance interval. -typical value in synchro is 8 seconds or more. -allowable range in synchro 3-840 sec. Total Split -total split is the current split time (G+Y+AR), in seconds for a particular phase. -usually assigned by synchro. At first set up minimum split and run Optimize-> Intersection Split command to allow synchro calculate total split. Allowable range in synchro 3-900 sec. Yellow Time and All Red Time -amount of time required for yellow and all red interval, respectively. -default yellow time value is 3.5 seconds and AR time 0.5 second. -default values can be altered by Options->Network Settings



Led/lag When default ring-barrier sequence is needed to change we can specify the lead/lag. Example : Default Ring Barrier sequence when East/West is main road

EBL- ø1 (protected)- Lead EBT- ø2- Lag EBR- ø2 (permissive)- Lag WBL- ø5 (protected)- Lead WBT- ø6- Lag WBR- ø6 (permissive)- Lag

NBL- ø3 (protected)- Lead NBTR- ø4- Lag SBL- ø7 (protected)- Lead SBTR- ø8- Lag

Allow Led/Leg Optimize This will allow synchro to adjust lead/lag to improve the traffic flow. If set ‘fixed’ user defined phase sequence will be maintained.

Recall Mode

• This is a way to set a recall for each phase.

• The recall modes available are:

• No Recall- When phase is allowed to skip.

• Min Recall- Phase will always appear with minimum but will never skip.

• Max Recall- Phase ill always show its maximum. Applicable when there is no detection. Phase can’t skip, gap out or be extended.

• Pedestrian Recall: Phase will always show walk phase . It will never skip or gap out until the walk and don’t walk intervals pass.

• Coordinaed Maximum or Minimum (C-Max or C-Min)-They are used for coordinated signals only. Phase shows the max or min time.

• Guidelines to set recall mode o Fully Actuated Signals- All pahses will have no recall or minimum recall o Semi-Actuated Signals” Main Street will have maximum recall. Side street will have no

recall o Actuated Coordinate Signal+ Set to Coordinated Recall Mode (max or min)

Derived Parameters Actuated Effective Green Average green time observed when signal is operating in actuated mode which is less than maximum green if phase is skipped or gapped out. Average of five percentile green times (includes Y+AR but exclude total lost time)

(Synchro calculated) actuated effective green time = ∑"#$%&$'()*$ +%$$' ,-.$/012

#$%&$'()*$ 34&*$ 5$'67( 89 ∗ ∑ :�� ;<�� =��

9 − >?>@A A?B> >CDE



Actuated g/C Ratio -this is calculated based on actuated effective green. Volume to Capacity Ratio

Volume to capacity ratio is calculated based on the actuated green times and cycle lengths (i.e. �

�(�/;))

Control Delay, Queue Delay, Total Delay, Level of Service -discussed before Approach LOS Approach delay is calculated as volume weighted average of the total delays for each lane group. Queue Length, Stops, Fuel Used: Discussed before



Phasing Window Input Parameters

Minimum Initial, Minimum Split -Already discussed; common component for timing and phasing windows Maximum Split -current split time in seconds. It is the longest amount of split time for actuated movements. -compare maximum split with percentile green time. -difference between Maximum Split & Total Split: Total Split is applicable for a particular movement. If a movement is assigned to multiple phases total split is the sum of individual splits. On the other hand, maximum split is the applicable for individual phases. Vehicle extension Minimum gap Time before reduce Time to reduce Walk Time Flash Don’t Walk -already discussed Pedestrian Calls (#/hr) -in case a pedestrian push button exists; the number of pedestrian calls per hour Dual Entry - as previously discussed if the phase can appear when another phase is showing in another ring and within barrier ‘Dual Entry’ is selected. In general, the through phases (i.e. even phases) are set ‘Yes’ and odd phases are set ‘No’. However, recall always has priority over dual ring. Inhibit Max -this is used for an actuated coordinate signal controller -If set Yes a non-coordinated phase can show more than the maximum time in case it starts early

Derived Parameters Percentile Green Time -these are the five percentiles for green times -for actuated signals, traffic conditions will be simulated based on these five percentile values. -the accompanying code indicates how the phase terminates (max-out, gap-out, skipped etc.)



Time-Space Diagram Window Time space diagram window can launch time-space diagram anytime for any arterial. An example is shown below. Here, Main Street can be considered as Arterial and we want to investigate vehicular movement in terms of their spatial and temporal distribution. Select Main Street and click the time-space diagram toolbar. T-S diagram will be drawn instantly.

There are a few characteristics about T-S Diagram -Inclined lines show vehicle in motion and the slopes represent the vehicular speed -The steeper the line the higher the speed. -Horizontal lines are vehicle stops. - The longer the horizontal line the more the control delay -if horizontal life goes beyond the green time it is an indication of queue delay. -TS diagram shows how progression can be achieved by manipulating green split along corridor and offsets to ensure a wider bandwidth



Introduction to SimTraffic The primary purpose of SimTraffic is to check and fine tune traffic signal operations. Thi is especially useful for analyzing complex situations that can not be easily modeled by macroscopic models; e.g.

o Closely spaced intersections with blocking problems o Progressive signal o Closely spaced intersections with lane change problems o The effects of signals on nearby unsignalized intersections and driveways o The operation of intersections under heavy congestion

Measures of effectiveness in SimTraffic

o SimTraffic Consider the following MOEs

o Slowing Delay Stopped Delay

o Stops

o Queue Length

o Speed

o Travel time an Distance

o Environmental parameters like: Fuel Consumption and efficiency

SimTraffic Parameters

Vehicles

-can assign different vehicle types and percentage of them -can put maximum speed, maximum acceleration, length, width and occupancy parameters

Drivers -Can simulate heterogeneous mixture of drivers based on their mode of decelerations, green reaction, headway at different speeds, gap acceptance factors etc.

Intervals -SimTraffic can generate report for different intervals

Data Options -reading volume and timing data from Universal Traffic Data Format (UTDF) files

Fuel Cars -For different acceleration and speed values fuel uses

Fuel Trucks -Fuel uses for Trucks Fuel Buses-Fuel uses for buses Emission Data: HC Emission, CO Emissions, Nox Emission

-For different speed and acceleration combination emission in mg/s



Simulation Control

Options available

• Real time playback

• Control frame speed of simulation

• Simulate and playing action together (slower)

• Record Simulation (faster to generate report)

• Stop playing or recording

• Erasing previous simulation history to generate a band new simulation run

• Multiple Simulation Run

Instantaneous Status

Signal Status

• Clicking on the middle of intersection shows the status of a signal timing .

Vehicle status

• Clicking a vehicle displays the status of a vehicle.

• Vehicle status can be used to help explain vehicle behaviors.

Signal Status Vehicle Status



SimTraffic Reports

File-> Create Report->Then Select -Selection Column (by approach, movement etc.) -Select one or more than the following options

• Simulation Summary

• Queuing Information

• Actuated Timing

• Performance Report -For performance reporting select the MOEs to Include -Select Multiple Run if you have already performed that before. Or you can select and record again

Multiple Run Reports



Simulation Summary Queuing Information

Actuated Timing Performance Report



PART C- EXAMPLE EXERCISES

Exercise 1: Isolated Intersection with Pre-timed Controller

Intersection of Main Street and First Street has the following traffic volume (during design hour) and

lane group configuration.

1a: Design an appropriate pre-timed signal phasing by Synchro with Dual Ring Four phase structure with all permissive left turn. 1b. Modify the design by a Dual Ring Eight Phase Structure with protected-permissive left turn. 1c. Compare the Level of Service in two cases.

• Which one you prefer in terms of level of service?

• Which on you prefer if you have an average of 5 left turn head on crashes/year? -Consider Pedestrian walk time as 5 second and flashing don’t walk time as 5 seconds.

250 ft

200 ft



1.a Solution

• Step 1 – Construction of Layout

• Open Synchro and Construct a simple intersection layout and name the East-west and

North-South Roadway

Step 2 –Lane Configuration

• Setup the lane configuration as per the layout shown below.

• Consider level grade and 12 ft on lane width for all lanes

• Set-up the approiate storage length, the storage lanes should automatically change

• Put an initial lost time of 3 sec.

• Since there is no detector leave the places lank.

• Consider Right Turn on red

Step 2 –Input Traffic Volume

• Input appropriate traffic volume for different turning volumes

• Keep the PHF (0.9), Heavy vehicles % (2%) fixed.

• Consider the input volume as the design traffic volume (no need to include any growth factor)

Step 3 –Input Timing /Phasing Feature Timing Window:

• Set Controller Type as Pretimed

• Since left turning are permissive place turn type for all Left turns

• There are two exclusive right turn for which we consider the permissive turn. Place appropriate code for them

• Put a Yellow time 3.5 sec and AR time 0.5 sec Phasing Window

• Check the yellow and all red time which you already assigned in Timing window

• Check the recall mode. It should be Max for all 4 phases since we already set controller type as pre-timed

• Check pedestrian walk and flashing walk time

• Check the dual entry as ‘Yes’ for all phases

Step-4 Optimize Cycle Length and Phase

• Click Optimize Cycle Length and optimize split Generate a Report 1.b Solution: In step 3 (i.e. Input Timing window)

• Change the left turning feature from permissive to protected and permissive for all four left turns.

• Keep the right turning as permissive. Place appropriate code for them

• Rerun Optimize-> Intersection cycle length

• Generate report



1.a Report 1.b Report



Exercise 2: Isolated Intersection with Actuated Controller

Now, the intersection experiences high traffic volume during morning peak hour for the eastbound through phase and the pre-timed controlled was needed to upgrade to actuated-control signal. The traffic volume during morning (7am -8 am)is shown below.

The detector configuration is as follows: Leading Detector for left turn lanes – 50 ft from stop bar Leading Detector for thru lanes – 300 ft from stop bar (for EB, NB and SB approach) and 350 ft for WB approach Trailing Detector on EB and WB thru lane – 144 ft from shop bar

Recall Mode: EB –WB directions will be considered coordinated and hence needed to operate in C-max recall mode. Pedestrian Phase: Also pedestrians are expected to cross all directions and hence all thru phases should consider pedestrian phase.

• Design an appropriate actuated control signal phasing by Synchro with Dual Ring Eight Phase Structure with protected-permissive leading left turn.

• Compare the Level of Service in pre-timed and actuated signal cases. • Generate the Quick Reports for Start of the Green Time • Run SynTraffic and Generate a report for every 15-minute intervals from 7.00 am – 8.00 am time period.



Solution

• Follow step 1 and 2( in 1.a) but for modified lane and volume scenarios. In step 1 put

appropriate value for the position of leading and trailing detectors

Step 3 –Input Timing /Phasing Feature Timing Window:

• Set Controller Type as Actuated Coordinated

• Place protected left turning for all Left turning movements

• Keep right turning as permissive turn.

• Put a Yellow time 3.5 sec and AR time 0.5 sec Phasing Window

• Put all left turning movement as lead except for north bound left

• Check the yellow and all red time which you already assigned in Timing window

• Put appropriate value for EB-WB thru phase the recall mode (C-max) .

• Put all other recall mode as none (note that for pretimed controlled all was placed in max recall mode)

• Check pedestrian walk and flashing walk time

• Check the dual entry as ‘Yes’ for all through phases (this is the basic feature for dual ring structure)

Step-4 Optimize Cycle Length and Phase

• Click Optimize Cycle Length and optimize split Step-5 Create Report in Synchro

• Generate a Report for overall LOS and delay

• Create a Quick report report from phasing window for Green Times



Step-6 Run SimTraffic and visualize

• Visualize the microscopic model based on your input for Synchro (Macrospic model) and based on the LOS/delay report



Step 7- Generate SimTraffic Report

Setting Interval: Options> Intervals and Volume> Click Insert 3 times> Put Duration Interval 15

minutes for 4 different bins> OK

• It will look like following:

• Record Simulation by pressing the top right hand corner button



SimTraffic Report by Intervals

7.00 am-7.15 am 7.15 am-7.30 am

7.30 am-7.45 am 7.45 am-8.00 am



Exercise 3: Closely Spaced Intersection with Single Controller

Main street crosses 1st and 2nd street at a distance of only 320 ft and a traffic engineer suggest having a

dual ring single controller.

The detector configuration is as follows:

Leading Detector for all lanes – 50 ft from stop bar

• Design with an actuated coordinated phase with EB-WB as direction for coordination.

• Generate a Time-Space Diagram and locate potential queue build-up for arterial.

• Run Simtraffic and verify queue build-up

Solution

Visualization Steps

� Construct link and node structure in Synchro

� Right Click on the link to write down the appropriate roadway name

� Set the link speed at 30 ft

� Click the lane window and put appropriate value for lane configuration



� After putting the lane configuration, click on the volume window toolbar to input the turning volumes (shown here)

� Click on the ‘Show lane on map’ to

confirm with the accompanying volume and lane configuration

� Click Option>Cluster Editor � Click both intersection in the small

widow of the cluster editor and add both of them in the right window list. In this way both intersection will be controlled by a single controller.

� Click the “Show Phase number node” and change them to ‘Standard’ phase number (similar to NEMA controller).

� Change the phase number � Optionally can edit phase template by

clicking Option>Phase templates>Edit Phase Templates



� Go to timing window and see if there is any conflict in phases. Is so then resolve the movement conflict.

� When conflicts are resolve for both intersection optimize cycle length and split (it requires to optimize only once since there is only one controller)

� Click on the time space diagram window to visualize the TS diagram

� Click “Queue” � Locate the potential queue build-up � we found that there is a ‘starvation for

EB thru traffic

� Run SimTraffic � We found that some portion of green is

wasted at intersection with 2nd street for EB thru traffic coming from 1st street- ‘starvation’



Exercise 4: Fixed Cycle Coordination

• For the Arterial Main street a coordinate cycle length of 100 sec has been suggested. Verify the

cycle length by Synchro

Solution

� Open file ‘Fixed Cycle Coordination’

� Optimize >Network Cycle Length.

� A window will appear � Select Cycle Length (50-150)

sec with 10 sec increments � Choose scope for ‘Entire

Network’ � Choose offset optimization as

medium � Choose Manual to see the

optimization report

� After running the optimization you will see the report

� It can be verified that 110 sec was a better option for cycle length (increased average speed, less dilemma vehicles, less fuel consumption and 2nd lowest total stops)

synchrosimtraffic handout

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