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AITPM presentation
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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
FUNCTIONAL SUMMARY APPROACH TO SCATS DATA
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
FUNCTIONAL SUMMARY APPROACH TO SCATS DATA
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
FUNCTIONAL SUMMARY APPROACH TO SCATS DATA
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?
ROUTE SCALE ANALYSIS
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
ROUTE SCALE ANALYSIS
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