ARCADY and PICADY modelling.
Roundabout and priority junction modelling in TRL’s Junctions software, with validated base models and results that hold up to scrutiny.
Also known as: ARCADY, PICADY, Junctions 10, Junctions 11, Junctions software, roundabout modelling, priority junction modelling
What’s included.
ARCADY models roundabouts and PICADY models priority junctions. Both sit within TRL’s Junctions software. Highway authorities use the results to judge capacity, queues and delay, and whether mitigation is needed.
- Geometry measured from survey or mapping
- Base year validation against queues
- Peak hour and profile options
- Future year scenarios
- Mitigation layouts
- Output summaries officers can follow
Straightforward, proportionate, agreed early.
Accurate geometry
Measured carefully, because small changes make big differences.
Validated
Checked against observed queues before any future year runs.
Plain results
RFC, queues and delay summarised in one clear table.
Questions we get asked
What is the difference between ARCADY and PICADY?
ARCADY is for roundabouts and PICADY for priority junctions. Both are modules within TRL’s Junctions software.
What RFC is acceptable?
Many authorities treat around 0.85 as practical capacity, but the policy test is whether the effect is severe, not a single threshold.
Which version of Junctions do you use?
The current release, and we can match the version the council uses if needed.
Often needed alongside.
Reading the results
ARCADY models roundabouts and PICADY models priority junctions. Both report how close each approach is to capacity, how long the queues are and how much delay drivers face, with and without the development.
- Ratio of flow to capacity (RFC), with around 0.85 commonly used as practical capacity.
- Queue lengths, in passenger car units, for each arm.
- Delay per vehicle, and how it changes with the development traffic.
- A check against observed queues, so the model reflects how the junction really works.
Last reviewed October 2026 by Ripple Development Planning. Policy and guidance change; for advice on a specific site, send us the details.
From our insights.
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