Roy Wilson

Methods For Assessing Traffic Flow Improvement Using SCATS Data

Australian Centre for Commercial Mathematics (ACCM)

Prepared for AITPM ConferenceAugust 2014

Authors: Roy Wilson (ACCM), Gordon Farrelly (RMS) , Christian Chong-White (RMS)

INTRODUCTION

1. INTRODUCTION TO THE PINCH POINT PROGRAM AND THE POST-IMPLEMENTATION REVIEW PROCESS

2. THE STUDY SITE – DESCRIPTION OF TRAFFIC ISSUES AND THE INTERVENTION

3. DESCRIBING THE FUNCTIONAL SUMMARY APPROACH TO SCATS DATA

4. A MODULAR MULTI-SCALE APPROACH TO ASSESSING NETWORK EFFICIENCY CHANGE

INTRODUCTION TO THE PINCH POINT PROGRAM AND THE PIR PROCESS

RMS PINCH POINT PROGRAM

1. Identify Pinch Points

2. Design Traffic Engineering Solution

3. Implement Engineering Works

4. Review Effects on Traffic Flow Efficiency(Post-implementation review)

INTRODUCTION

POST-IMPLEMENTATION REVIEW

1. IDENTIFICATION STAGEIdentify the Crucial Traffic Flow

Efficiency Questions

2. ANALYSIS STAGEDetect and Quantify the Effect of the

Project on Traffic Flow Efficiency

3. INTERPRETATION STAGEInterpretation of the Results within the

Engineering, Management and Economic Contexts

INTRODUCTION TO THE PINCH POINT PROGRAM AND THE PIR PROCESS

INTRODUCTION

PIR– Analysis Stage

Difficulties with analysis:

1. Wide range of diverse intervention scenarios

2. Data availability can be limited

3. Complex dependency patterns in urban traffic networks

4. Dynamic time dependency on unmeasured or unknown variables

5. High level of noise (randomness)

6. System complexity can make relationships between cause and effect unclear

THE STUDY SITE

INTERSECTION OF PRINCES HWY AND PRESIDENT AVENUE KOGARAH

• Major route linking the southern suburbs of Sydney with the CBD

• High traffic demand (particularly during AM peak)

• Close proximity to a major hospital, TAFE and schools

THE STUDY SITE

OVERVIEW OF THE PINCH POINT PROGRAM CHANGES

BEFORE AFTER

THE STUDY SITE

TRAFFIC MANAGEMENT ISSUES AT THE SITE

• Capacity constraints not meeting high demand

• Select sharing of lanes between movements (inefficient use of green time)

• Queuing affected efficiency of up-stream intersections

CASE STUDY

PIR QUESTIONS OF INTEREST

Question Scale

Did the intervention result in an increase in flow and a reduction in congestion along a defined south-north route along the Princes Highway during the AM peak period?

Route

Did the intervention result in an improvement in intersection throughput at the Pinch Point intersection?

Intersection

What were the effects of the intervention on the flow characteristics of the surrounding network Network

FUNCTIONAL SUMMARY APPROACH TO SCATS DATA

SCATS DATA FEATURES

DATA COLLECTED AND STORED DURING NORMAL NETWORK OPERATION (READILY AVAILABLE)

HIGH VOLUME DATA PROVIDES INFORMATION FOR EVERY GREEN PHASE IN THE NETWORK

SCATS IS DESIGNED TO OPTIMISE NETWORK EFFICIENCY AND SO IT STORES IMPORTANT NETWORK EFFICIENCY INFORMATION

Database


SUMMARISE THE DATA AS FUNCTIONS

ONE FUNCTION IS ESTIMATED FOR EVERY DETECTOR (LANE) FOR EVERY DAY

EACH FUNCTION IS A BUILDING BLOCK THAT CAN BE USED TO ANSWER A WIDE RANGE OF TRAFFIC QUESTIONS OVER A WIDE RANGE OF SCENARIOS

A FLEXIBLE MODULAR APPROACH

THE FUNCTIONS ARE ANALAGOUS TO THE FUNDAMENTAL DIAGRAM

SOLID BASIS IN TRAFFIC ENGINEERING THEORY


A BRIEF REVIEW OF THE FUNDAMENTAL DIAGRAM

A – LOW FLOW DUE TO LOW DEMAND

B – MEDIUM FLOW AS DEMAND INCREASES

C – OPTIMAL FLOW DEMAND IS RELATIVELY HIGH

D – DEMAND BECOMES TOO HIGH FLOW BECOMES SUB-OPTIMAL


A BRIEF REVIEW OF THE FUNDAMENTAL DIAGRAM

CRITICAL OC

EXPECTED MAXIMUM

FLOWCRITICAL OCCUPANCY (OC)ONCE THE CRITICAL OC HAS

BEEN PASSED FLOW IN THE LANE WILL TEND TO BECOME SUB-OPTIMAL

EXPECTED MAXIMUM FLOWEXPECTED FLOW FOR A GIVEN

LANE UNDER OPTIMAL TRAFFIC DEMAND CONDITIONS

FD UTILISATIONREPRESENTS THE PROBABILITY

THAT A DRIVER WILL EXPERIENCE SUB-OPTIMAL FLOW CONDITIONS DURING A GIVEN TIME PERIOD

ROUTE SCALE ANALYSIS

Did the intervention result in an increase in flow and a reduction in congestion along a defined south-north route along the Princes Highway during the AM peak period?


FLOW CHANGE ANALYSIS

1400 Veh/r 1600 Veh/r

14% Increase in Expected Maximum Flow

ARIMA INTERVENTION ANALYSIS TAKES INTO ACCOUNT

• SEASONALITY• WEEKDAY EFFECTS• HOLIDAYS


CONGESTION ANALYSIS

3.6% 2.7%

A significant reduction in the proportion of drivers exposed to sub-optimal flow conditions ARIMA INTERVENTION ANALYSIS TAKES INTO ACCOUNT

• SEASONALITY• WEEKDAY EFFECTS• HOLIDAYS

CHANGE IS NOT STATIONARY OVER TIME. MAY BE DUE TO THE INDUCED DEMAND EFFECT

INTERSECTION SCALE ANALYSIS

OPTIMAL HOURLY INTERSECTION THROUGHPUT (OHIT)A MEASURE OF HOURLY THROUGHPUT THROUGH THE INTERSECTION UNDER OPTIMAL DENSITY CONDITIONS

5900 Veh/hr

8180 Veh/hr

38-40% Increase in OHIT

NETWORK SCALE ANALYSIS

NETWORK SCALE ANALYSIS

• FLOW IMPROVEMENT AT THE TREATMENT INTERSECTION (979) IS VERY SIGNIFICANT (AS EXPECTED)

• IMPROVED FLOW CONDITIONS FOR NORTH-BOUND TRAFFIC ON THE PRINCES HIGHWAY

• SOME IMPROVEMENT FOR NORTH-BOUND TRAFFIC ON ROCKY-POINT ROAD

• NO DISCERNABLE IMPROVEMENT FOR FLOW CONDITIONS ON PRESIDENT AVENUE

• FLOW CHANGE STORY AROUND MINOR ROADS IS MIXED

CONCLUSION

SCATS DATABASE

LEVERAGE SCATS DATA STATISTICAL “BIG DATA” ANALYSIS TECHNIQUES

FLEXIBLE MODULAR APPROACH

PRACTICAL OUTCOMES FOR MANY TRAFFIC QUESTIONS

Business

Roy Wilson