SIDRA intersection capacity analysis
The data-driven case that convinces council your intersection will actually perform.
SIDRA Intersection is the industry-standard analytical software for detailed, lane-by-lane modelling of traffic flow at intersections, roundabouts, and signalised networks — mandated by most Australian road authorities, including TfNSW, for development applications affecting intersection performance.
What SIDRA measures
| Metric | What it means / benchmark |
|---|---|
| Level of Service (LoS) | An A–F grade for how well an intersection is operating — A is free-flowing, F is gridlock. Benchmark: LoS D or better in peak periods. |
| Degree of Saturation (v/c ratio) | How close the intersection is to its capacity limit. Benchmark: below 0.90. |
| Average Delay | Average time a vehicle is stopped or slowed at the intersection. Assessed against LoS. |
| 95th Percentile Queue | The practical maximum queue length, in metres, not exceeded 95% of the time. Must not block driveways or upstream intersections. |
Process
- 01
Data collection — traffic counts across weekday AM and PM peaks, site geometry, and signal phasing from the relevant authority
- 02
Model build & calibration — calibrated against observed on-site conditions
- 03
Scenario testing — a “do nothing” case compared against a “do something” case across opening year and future design horizon
Common questions
Is SIDRA analysis required for every development application?
No — it depends on project scale and anticipated traffic generation, as determined by the relevant council or road authority.
How does SIDRA differ from simulation software?
SIDRA suits detailed, lane-by-lane analysis of individual intersections. Simulation platforms model vehicle-by-vehicle behaviour across larger networks — better suited to queue spillback or multi-intersection interactions.
Does SIDRA account for pedestrians and cyclists?
Yes — delay, Level of Service, and crossing time outputs are produced for pedestrians and cyclists as well as vehicles.
What happens if the analysis shows LoS E or F?
It indicates mitigation is required — signal phasing changes, lane reconfiguration, or a physical upgrade — which are modelled to demonstrate a credible path to an acceptable Level of Service.
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