Heuristic Methods
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Transcript Heuristic Methods
Limitations of Adaptive Control
David Hale
University of Florida
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Ineffective heuristic methods
Ineffective at certain congestion levels
Lack of accountability
Low market share
Competing technologies
Heuristic Methods
Fast, but ineffective
Equisat (SCATS)
Greedy algorithm (InSync)
Hill-climb (TRANSYT)
Slow, but effective
Simulated annealing
Genetic algorithm
Derivative-free methods
Improvement Percentage (%)
35.0
30.0
25.0
SA
HC
GA (T)
GA (R)
20.0
15.0
10.0
5.0
0.0
0.0
50.0
100.0
Run Time (seconds)
150.0
z
y
C
Optimality
B
x
A
Run Time
Delay
Increased Complexity
Signal Timing
Adapting vs. Optimizing
Non-Adaptive,
Quasi-Adaptive
Quick Optimization
Thorough Optimization
Synchro, T7F,
Vistro
HCS-Streets, T7F,
Vistro, ArteryLite
Fully Adaptive
SCATS, InSync
(none)
Accountability
Capacity analysis? NO
Simulation? DIFFICULT
Most simulation products can’t do it
VISSIM API = extra $$$
High level of expertise
Time-consuming
Expensive
Market Share
Decades of availability (1960’s)
SCATS (1976), SCOOT (1981)
Fewer than 5% of signals
Why?
Costs too high?
Uncertainty about benefits?
Lack of accountability?
Competing Technologies
Data-driven
Quasi-adaptive
Stronger algorithms
“automated performance measures
allow agencies to optimize and
manage signals without extensive
field data collection, a central traffic
management or adaptive system, or
a communications infrastructure”
Limitations of Adaptive Control
David Hale
University of Florida