We undertake junction modelling to assess how existing and proposed junctions are likely to operate with development traffic. Using industry-standard tools such as PICADY, ARCADY and LinSig, we provide clear, evidence-led insight into capacity, delay and queuing.
Junction modelling is often a key component of planning submissions and is regularly scrutinised by Local Highway Authorities, National Highways and other consultees.
What is junction modelling?
Junction modelling uses recognised software to simulate how junctions perform under different traffic scenarios. PICADY and ARCADY are typically used for priority and roundabout junctions, while LinSig and Transyt are used for signal-controlled junctions and networks.
These models help quantify operational performance, identify capacity constraints and test the effectiveness of mitigation measures, forming a core part of Transport Assessments and technical evidence to support development proposals.
Our junction modelling work is tailored to the site and assessment needs and typically includes:
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Selection of appropriate modelling tools (PICADY, ARCADY, LinSig or Transyt)
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Development of baseline and future year models using survey data and growth factors
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Incorporation of development traffic
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Incorporation of development traffic and background growth
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Sensitivity testing where appropriate
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Testing of mitigation options and design changes
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Written interpretation of performance and implications
The value of effective junction modelling lies not just in running software, but in applying professional judgement to ensure models reflect real-world operation. By building proportionate, transparent models, we help clients understand whether capacity issues are genuine, marginal or unlikely to influence deliverability. This approach supports focused mitigation design, avoids unnecessary complexity and ensures that modelling evidence is credible and defensible. Clear interpretation of results also helps bridge the gap between technical outputs and planning decision making, supporting constructive engagement with highway authorities.
When junction modelling is needed
Junction modelling is commonly undertaken:
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To support Transport Assessments or Statements
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Where development traffic affects priority, roundabout or signalised junctions
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Ahead of or during pre-application discussions
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To test mitigation options and design iterations
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For developments impacting sensitive or constrained networks
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As part of post-application negotiation with consultees
It is particularly important where junction performance is a key planning consideration.
Our approach
We take a clear, proportionate approach to junction modelling:
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Understand the development proposals and traffic forecasts
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Select the most appropriate modelling methodology
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Build transparent, well-documented models
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Test forecast scenarios and sensitivities
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Interpret results clearly and advise on next steps
Our focus is on producing modelling that informs decisions rather than obscuring them.
Who we support
We undertake junction modelling for:
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Residential and mixed-use developments
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Commercial and employment sites
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Retail and leisure schemes
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Education and healthcare facilities
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Strategic land and large-scale developments
Our experience across England, Scotland and Wales ensures modelling aligns with local authority and National Highways expectations.
Need junction modelling to support your planning submission?
Get in touch and we will provide clear, proportionate modelling using PICADY, ARCADY, LinSig or Transyt.
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