ENGINEERING – TRANPORTATION ENGINEERING CALCULATOR
Signalised Intersection Phasing
A precise tool.
What is the Signalised Intersection Phasing & How does it work?
Signalised intersections use timed phases to allocate rightβofβway to competing movements. By synchronising red, yellow and green indications, engineers can reduce stops, improve safety and increase overall corridor capacity.
The length of a signal cycle (C) is divided among approaches based on observed traffic volumes (V_i). A common proportional method assigns green time (G_i) using the formula shown below, ensuring that higherβvolume approaches receive longer greens.
Pedestrian crossing intervals and coordination with adjacent signals are added as fixed or actuated phases. Proper phasing balances vehicular flow with pedestrian demand while maintaining acceptable delay.
G_i = \frac{V_i}{\sum V}\times C
G_i = green time for approach i (seconds)
Parameters
Result
β
Frequently Asked Questions
How do I calculate green time for a signalised intersection?
Use the formula G_i = V_i / Ξ£V, where G_i is the green time for an approach, V_i is the observed traffic volume for that approach, and Ξ£V is the total of all traffic volumes.
What factors affect the length of a signal cycle?
The length of a signal cycle (C) is influenced by the number of approaches, their respective traffic volumes, and the desired balance between green time and yellow/red light durations.
How does synchronising red, yellow, and green indications improve safety?
Synchronisation helps reduce stops at intersections, which decreases the likelihood of accidents by reducing conflicts between vehicles entering from different directions.
Can this calculator handle multiple approaches?
Yes, the formula G_i = V_i / Ξ£V can be applied to each approach individually, ensuring that higher-volume approaches receive proportionally longer green times.
What is the purpose of a signalised intersection phasing calculator?
The calculator helps engineers allocate right-of-way efficiently by determining optimal green light durations for different traffic movements at intersections.
How does this method ensure that all approaches are served fairly?
By using the observed traffic volumes (V_i) to proportionally assign green times, higher-volume approaches receive longer greens, ensuring that all movements have sufficient time to proceed safely and efficiently.
Can I use this calculator for unsignalised intersections as well?
No, this calculator is specifically designed for signalised intersections where traffic lights control the flow of vehicles. Unsignalised intersections typically rely on stop signs or yield signs.
Results are for informational purposes only and do not constitute professional advice.