Traffic signal timing is crucial for optimizing traffic flow and minimizing delays at intersections. It involves allocating green time to different movements and coordinating signals along streets or in networks for smooth vehicle progression.
Key parameters like cycle length, split times, and offsets are adjusted based on traffic demand. Various control systems, from fixed-time to adaptive, are used. Strategies must balance different road users' needs while considering safety and special conditions.
Traffic signal timing principles
Allocation of green time and coordination
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Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Top images from around the web for Allocation of green time and coordination
Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Traffic signal coordination control along oversaturated two-way arterials [PeerJ] View original
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Traffic signal timing allocates green time to different traffic movements at intersections optimizing traffic flow and minimizing delays
Coordination of traffic signals along arterial streets or in networks provides smooth progression of vehicles through multiple intersections
Key parameters in signal timing adjusted based on traffic demand and roadway characteristics
Cycle length
Split times
Offsets
Phase sequences
Traffic signal control systems
Traffic signal controllers use various timing modes with specific applications and benefits
Fixed-time control
Actuated control
Adaptive control systems
Level of service (LOS) evaluates the performance of signalized intersections considering factors
Delay
Number of stops
Balancing user needs and special considerations
Signal timing strategies balance needs of different road users while considering safety and environmental impacts
Vehicles
Pedestrians
Transit
Traffic signal preemption and priority systems accommodate special traffic conditions within signal timing framework
Emergency vehicles
Transit vehicles
Other special conditions (railroad crossings)
Signal timing and traffic performance
Impact of cycle length and split times
Cycle length affects intersection capacity, delay, and queue length
Longer cycles generally increase capacity
Longer cycles potentially increase delay for minor movements
Split times determine proportion of green time allocated to each phase impacting
Capacity for individual traffic movements
Delay for individual traffic movements
Volume-to-capacity (v/c) ratio relates traffic demand to available capacity provided by signal timing
Offsets and coordination performance
Offsets between adjacent signals influence progression quality affecting
Travel time along arterial corridors
Number of stops along arterial corridors
Fuel consumption along arterial corridors
Performance indices evaluate effectiveness of coordination along arterial streets
Progression Ratio (PR)
Bandwidth Efficiency
Intersection delay and queue management
Intersection delay influenced by multiple timing parameters
Cycle length
Green time allocation
Coordination settings
Queue length and spillback affected by timing parameters particularly in closely-spaced intersections
Green time allocation
Cycle length
Offset settings
Coordinated signal timing plans
Time-space diagrams and system cycle length
visualize and design coordinated signal timing plans showing relationship between
Distance
Time
Signal states
System cycle length selection crucial for coordination
Based on critical intersection's requirements
Considers network-wide impacts
Offset optimization and progression strategies
Offset optimization techniques determine best relative timings between intersections
Maximizing bandwidth
Minimizing delay
Traffic signal coordination strategies with specific applications and trade-offs
One-way progression
Two-way progression
Flexible progression
"Early return to green" concept impacts coordination in actuated signals
Multiple timing plans and special considerations
Multiple timing plans developed to address varying traffic patterns
Time-of-day schedules
Traffic responsive plan selection
Special considerations for coordinated timing plans
Accommodating pedestrian crossings
Transit priority
Oversaturated conditions
Signal timing effectiveness evaluation
Performance measurement techniques
Before-and-after studies assess impact of signal timing changes measuring key performance indicators
Travel time
Delay
Fuel consumption
Field data collection methods provide empirical evidence of signal timing performance
Floating car studies
Bluetooth sensors
Video analysis
Simulation and analysis tools
Microscopic traffic simulation software models and evaluates complex signal timing scenarios (, Aimsun)
Macroscopic analysis tools optimize signal timings and evaluate coordination strategies (, TRANSYT)
Progression quality and economic impact assessment
Performance measures evaluate quality of progression in coordinated systems
Arrival Type
Platoon Ratio
Queue Discharge Flow Rate
Benefit-cost analysis quantifies economic impact of signal timing improvements considering factors
Delay reduction
Fuel savings
Emissions reductions
Automated traffic signal performance measures (ATSPMs) allow ongoing evaluation and fine-tuning of signal timing strategies
Key Terms to Review (4)
Queue length: Queue length refers to the number of vehicles waiting in line at a given point in time, often measured at intersections, merging points, or other areas where vehicles must stop or slow down. This concept is crucial as it directly impacts traffic flow, delays, and overall system efficiency. Understanding queue length helps in analyzing congestion patterns and is essential for effective traffic management strategies.
Synchro: Synchro refers to a system or method used in traffic engineering to synchronize traffic signals at intersections and along corridors. This synchronization helps to optimize traffic flow, reduce delays, and improve overall safety for vehicles and pedestrians. By coordinating signal timing, synchro minimizes stops and starts, leading to more efficient movement of traffic and enhancing intersection capacity.
Time-Space Diagrams: Time-space diagrams are graphical representations that illustrate the relationship between time and distance for vehicles or pedestrians moving through a transportation network. These diagrams help visualize traffic flow, identify patterns in movement, and analyze interactions between different transportation elements, making them essential tools for studying queuing behavior and traffic signal coordination.
VISSIM: VISSIM is a microscopic traffic simulation software developed by PTV Group, used to model and analyze traffic flow at a detailed level. This tool allows engineers to create realistic simulations of traffic behavior, which can inform intersection capacity analysis, traffic signal timing and coordination, as well as performance assessments of different traffic scenarios. VISSIM's ability to simulate individual vehicle movements and interactions makes it a vital resource for understanding complex traffic conditions and optimizing transportation systems.