Coordinated Signal Software Evaluation - AITPM ... AITPM B2B6 7 Halcrow Wilson... · Coordinated Signal Software Evaluation ... • Satisfaction that algorithms are as good or better

1 Coordinated Signal Software - Chris Wilson and Simon KinnearNovember 10

Coordinated Signal Software Evaluation

Offline Optimisation Tools for SCATS

Chris Wilson

Simon Kinnear

November 102 Coordinated Signal Software - Chris Wilson and Simon Kinnear

Background

• RTA appoints Halcrow to undertake an

assessment of RTA coordinated signal

software needs, Nov 08.

• Halcrow facilitate several workshops and

undertake some practical applications of

coordinated signal software, Dec 08-

Mar10.

• Based on study findings RTA begin

dialogue with JCT Consultancy

manufacturers of LinSig, Apr10 – ongoing.

• Aug 10, RTA issue letter stating:

“…LinSig v3.0 (SCATS) is most

appropriate alternative to SCATES for

coordinated signal operation.”


RTA Requirements

• Sydney Coordinated Adaptive Traffic Signals (SCATS) requires

offline offset optimisation and RTA responsible for growing number

of signals (3300+).

• RTA looking for modern, intuitive software to provide quick

assessments of offline coordination.

• RTA staff require understanding of linked signal operations to

assist:

• Network Operations; and

• Review Consultants’ DA Supporting Evidence.

• Simple model verification and flexible reporting.


Desirable Features of Replacement Software

• Simple conversion of SCATES data files into replacement

software’s format (large library of RTA files).

• Conversion of replacement software output into SCATS

data.

• Satisfaction that algorithms are as good or better than

SCATES.

• Model red arrows and trailing turns.

• Regional settings to adjust terminology if needed.

• Similar outputs to SCATES, e.g. stops, delays.

• Economic analysis capability.

• Visualisation of network operation as a check on the

model.


SCATESPrincipal Author: Arthur Sims

Commercial Development in 1980s at RTA


Background

• SCATES calculates optimum phasing designs, phase splits and cycle

lengths for traffic signals, and calculates optimum offsets for linear

and network coordinated traffic signal systems, providing offset and

split data for SCATS.

• Halcrow has extensive experience in the application of SCATES to

existing and proposed traffic signal systems, and can utilise the

SCATES program for:

• determination of warrants for signal co-ordination

• analysis of road design projects involving multiple signal controlled

intersections that interact

• hourly and annual delay, costs, fuel and total annual operating costs

• analysis of phasing designs for isolated or coordinated intersections.


SCATES did what it was asked to do…

SCATES -> SCATS Data Exchange Features:

• Stretch phase specification;

• LoS at each intersection and approach;

• Pre-defined intersection types

• Signal sequences from SCATS phase library;

• Delay to turning traffic due to pedestrians crossing explicitly modelled;

• Import LX (Cycle lengths, splits data, PP data and LP data);

• Turn bay length requirements;

• Mode for normal SCATS split plan or incremental splits operation;

• Pedestrian crossing Data (PX); and

• Annualised costs of intersection operation


SCATES GUI and Reporting


Simple Isolated Traffic Signal Concepts

1. Movements -> Phases

Movements Phases

Phase Time

(Green Time + Yellow Time + All Red Time)

Effective green time

Flo

w r

ate

pcu/h

r

Clearance

lost time

Time

Start Up lost time

Saturation

Flow Rate

@ Each Signal Head

SCATS GUI

2. Phase Times (splits)

3. Cycle Time


Linked Traffic Signal Concepts

1. Time Distance Diagram

Time Distance Diagram

S1 S2

Start Green S1

Start Green S2

Offset (s)

2. Offsets


3. Platoon Dispersion

0m 100m 300m 500m 700m 1000m

Time

Flo

w R

ate

as

% S

atu

rati

on

Saturation Profile Arrival Profile

4. Cyclic Flow Profiles

Departure Profile

Linked Traffic Signal Concepts contd.


Signal Design - The RTA Way or the Highway

RTA objective is to promote safety and optimise capacity signalised

intersection design in the following way:

• Minimise no. of phases (make best use of time available)

• Minimise cycle time

• Run as many compatible movements as possible together

• Restrict each phase to non-conflicting movements

• Allow each movement to run in as many phases as possible

Source: RTA Traffic Signal Design – Section 7 Phasing & Signal Group Display Sequence

Other useful references:

•Traffic signal operation (New South Wales, Australia) RTA-TC-106

•Standard for Single Diamond Overlap Phasing-Guidelines for Developing, TS-TN-026, RTA

•Austroad Guide to Traffic Management Part 9: Traffic Operations

•General Principles of Traffic Control by Light Signals, Dept of Transp. Traffic Advisory Leaflet 1/06


Consultants need to be aware of RTA preferences

When to introduce:

• Pedestrian protection

• Split approach

• Double Diamond Overlap

• Leading/Trailing/ Filtering/Non Filtering Turns

• LTOR

Design has to fit in with:

• Local timing settings

• Overall SCATS Network Settings


3 Study Networks

1. Market Street, Sydney CBD

2. Parramatta Road, Haberfield

3. Spit-Military Road, Mosman


Analytical Framework

Area of Assessment Assessment Criteria

Network

Description

Ability of software to deal with NSW road characteristics and signal control standards. Criteria will

include:

NSW terminology

left turns through pedestrians

Short Lane overspills

Left Turn on Red

Modelling of SCATS

Model

Complexity

Assessment of the detail to which each package models the network, including:

Qualitative assessment of the relative time required to build the model network

Input requirements

Practical network sizes

Model runtimes

Traffic Assignment

Congested

Conditions

The ability of each package to replicate the conditions associated with a congested network. This

includes:

Exit blocking at intersections

Saturation flow adjustments

‘Wasted’ green time (i.e. more green time than can be used, due to downstream congestion)

Journey TimesThe ability of each package to replicate actual network journey times. Travel times derived from

RTA E-Tag readers and in-car journey times from 2007 along the corridor will be used as a

comparison.

Reporting

A comparison of the model outputs, including:

Report formats

Level of Service outputs

Ease of manipulation of data tables


Key Features Comparison

Network Feature

SCATES TRANSYT13 LinSig 3.0

CTM Model PDM Model

Exit blocking

Traffic assignment 4 2 2 1

Model runtimes 1 3 1 4

Practical network size limits 3 1 1 4

Automatic saturation flow adjustment

Report format 4 2 2 1

Use of Australian terminology

Short lane queue spill back

Left turn through Pedestrians

Short lanes

LOS

Specifically Modelled Not Modelled Can be Modelled With Some Effort

Ranking 1-4 (1 Best – 4 Worst)


Spit-Military Road

13

2

4

5

7

6

8

14

15

9 10 11

12

13

16

17

12 Signalised Intersections

5 Pedestrian Crossings

5 km of Arterial Road


13

2

4

5

7

6

8

14

15

9 10 11

12

13

16

17

Study Results

Inbound E-Tag Journey Time Comparison (Medusa St to Belmont St)

Observed

RR67 Un-calibrated Model

Journey Times (mins:secs)

SCATS Calibrated Model Journey

Times (mins:secs)

SCATES LinSig TRANSYT SCATES LinSig TRANSYT

Inbound In-Car Journey Time Comparison (Parriwi Rd to Ben Boyd Rd)

9:47 7:05 8:16 7:00 7:32 11:15 9:19

Outbound In-Car Journey Time Comparison (Ben Boyd Rd to Parriwi Rd)

9:03 8:26 7:31 7:37 10:26 8:54 8:08

5:38 4:32 5:26 4:32 4:55 6:17 5:25


TRANSYT13

TRL, Crewthorne, UK since 1967


Background

• The grandfather of coordinated signal software – pedigree in academic

research

• Large networks easily modelled (up to 200 nodes, 1000 links)

• 2 traffic models – Platoon Dispersion Model, Cell Transmission Model

• Most widely adopted throughout the world

• Formed the basis for TRANSYT-7F (US)

• Was academically driven, now commercial product


• Complex flared approaches and adjacent lane blocking

• Explicit identification of pedestrian and tram links

• Ability to enter custom parameters for bus and tram links

Key Features

Bus Parameters

85300.471570

Travel Time

Coefficient2

Travel Time

Coefficient1

Acceleration

(ms^[-2])

Dispersion

Coefficient2Dispersion

Coefficient1

Tram Parameters

85300.47070

Travel Time

Coefficient2

Travel Time

Coefficient1

Acceleration

(ms^[-2])

Dispersion

Coefficient2Dispersion

Coefficient1

• Intuitive network building

• Cell-transmission model (CTM) enables specific analysis of blocking

• Time-varying flows

• Analysis sets and multiple demand sets


Cell Transmission Model

• Models spatial as well as temporal extent of queues

• Divide road space into “cells”, and time into steps

• “Transmit” traffic from cell to cell at each time step

cell 1 2 3 4 5 ... ...

Cell Flows and Occupancy from CTM

Visual Display of CTM


TRANSYT User Interface


TRANSYT14

• Isolated signal controlled

intersections

• Degree of saturation

penalties

• New lane and traffic stream

structure

• New signal timings mode

• Controller stream (separates

signal groups from network

structure)

• Phase or signal group

optimisation

• RR67 saturation flow

estimation by lane


LinSig 3.0

JCT Consultancy, Lincoln, UK since 1980s


Background

• Controller specific limitations placed on phasing.

• Individual lanes (not links) modelled.

• Intuitive to use for the traffic engineer/modeller.

• Only small networks can be modelled (up to 20 nodes, 100 links).

• Calculates vehicle routing over entire network.

• Undertakes matrix estimation.

• Now direct competitor to TRANSYT .


SCATS Based Terminology

Phases View

SCATS Based

Terminology

Mode Indicator

Signal Groups


LinSig User Interface


LinSig Reporting and Model Verification

• Print user definable areas,

labelling, notes etc.

• Report Builder (RTF

format) allows user

defined tables, graphics to

be presented together.

• Export graphics to CAD,

Word etc.

• Cyclic Flow profile graphs.

• Queue and Storage graphs.

Flow Deficit due to

insufficient flow on

a route between B-A


SCATS Opportunities

Using SCATS data to calibrate models


SCATS Traffic Reporter - Counts

Self Calibrating Models

SCATS Stop line detectors are very useful:

4.5

m

1.5 m

4.5

m

11.0 m

Typical layout for Stop-line loop

Call only

Call and extendCall and extend

Dividing line

Stop-line

Lane line

Kerb line

• Maximum Flow (MF) –maximum flow across stop line

• Degree of Saturation (DS) – SCATS calculates a DS every cycle

• VK –maximum number of vehicles that clear stop line

• VO – number of vehicles that did cross stop line

SCATS Data Continuously Collected


Variation of ratio of Vo/Vk as Degree of Saturation Increases

Large vehicles or fast moving traffic

Practical range up to DS 100%

Lane Blocking for DS>100%

and Ratio Vo/Vk < 1


Variation of Vo and Vk over 24 hour period

Variation of Degree of Saturation over 24 hour period

Vo, Original Volume

Vk, Reconstituted Volume

Due to exit blocking


Summary & Conclusions

• RTA have adopted LinSig 3.0 software for analysis of coordinated

signal operation.

• RTA have their own unique requirements for software that can be

utilised with SCATS.

• SCATES has all the necessary features but has not moved on in

recent years.

• UK software (TRANSYT and LinSig) has a long pedigree of

application and research that can be modified for Australian

terminology and signal operation.

• Like any model the skill of the modeller is paramount as default

settings are NEVER adequate and RTA need calibrated models.

Documents

Coordinated Signal Software Evaluation - AITPM ... AITPM B2B6 7 Halcrow Wilson... · Coordinated Signal Software Evaluation ... • Satisfaction that algorithms are as good or better