A request from Council for a SIDRA analysis is a standard and critical component of many development applications. For developers, architects, and project managers, this can present a significant challenge: interpreting complex technical outputs to justify an intersection design and avoid traffic-related objections. Without a clear understanding of the methodology and its metrics, you risk delays or potential rejection of your DA. The core requirement is to demonstrate with hard data that your development’s traffic impact is manageable and that proposed access points will operate efficiently and safely.
This practical guide demystifies the process. We provide a direct overview of an Intersection Operations Assessment using SIDRA, the industry-standard software for this analysis in Australia. You will learn precisely what SIDRA is, the key performance indicators it measures-including Level of Service (LoS), degree of saturation, and average delay-and how these results provide the objective data required by local authorities. Our objective is to equip you with the knowledge to confidently interpret your traffic impact assessment and secure council approval for your project.
Key Takeaways
- Understand how SIDRA software provides an objective, data-driven analysis of intersection performance, replacing subjective opinion with verifiable facts.
- Learn to interpret the core performance metrics produced by SIDRA, giving you a clear understanding of how a council will judge an intersection’s efficiency.
- Recognise the critical steps involved in a professional Intersection Operations Assessment using SIDRA, ensuring the data submitted is robust and credible.
- Leverage the SIDRA report as a powerful tool to justify your design choices and proactively address council concerns, streamlining your development application approval.
What is SIDRA INTERSECTION and Why is it the Industry Standard?
SIDRA INTERSECTION is a micro-analytical traffic engineering software used for the detailed modelling of traffic flow at intersections, roundabouts, and signalised networks. Its primary function is to simulate and predict network performance, providing quantifiable data on capacity, level of service, and delay. As a foundational tool for traffic impact assessments, it enables engineers to evaluate existing conditions and forecast the impacts of proposed developments. Developed in Australia, the Sidra Intersection software is recognised as the definitive industry standard for this type of analysis.
For a practical introduction to the software’s basic functions, view the following tutorial:
Unlike simpler traffic models that provide generalised outputs, SIDRA conducts a detailed, lane-by-lane analysis. This granular approach is why it is mandated by most state and local road authorities, including Transport for NSW (TfNSW) and the Victorian Department of Transport and Planning (formerly VicRoads). The software’s outputs form the technical basis of any robust Intersection Operations Assessment using SIDRA, ensuring that proposed designs are scrutinised against established performance criteria before approval.
Core Capabilities of SIDRA
SIDRA’s advanced modelling engine provides a comprehensive analysis by accounting for numerous real-world factors. Its key capabilities include:
- Modelling Versatility: Accurately models a wide range of control types, including signalised intersections, single and multi-lane roundabouts, and sign-controlled (give-way or stop) intersections.
- Complex Variable Analysis: Incorporates variables such as different vehicle types (heavy vehicles, buses), pedestrian crossing movements, and roadway gradients that affect vehicle performance.
- Behavioural Simulation: Simulates complex driver behaviours and vehicle-to-vehicle interactions with a high degree of accuracy, based on extensive research.
- Detailed Performance Outputs: Generates lane-specific outputs for metrics like delay, queue length, travel time, and level of service (LoS), providing a precise understanding of operational efficiency.
Why Councils and Road Authorities Trust SIDRA
The widespread adoption of SIDRA by government bodies is based on its reliability and the objective nature of its outputs. Authorities trust the software because:
- It provides a consistent and repeatable methodology, ensuring all traffic impact assessments are evaluated against the same standard.
- The software is founded on decades of peer-reviewed Australian research, making its traffic and driver behaviour models highly relevant to local conditions.
- Its detailed reports allow for an objective comparison between different design options (e.g., a roundabout vs. a signalised intersection), enabling evidence-based decision-making.
- It helps authorities ensure new developments will meet established performance benchmarks and not degrade the safety or efficiency of the existing road network.
Key Performance Indicators: Understanding the SIDRA Outputs
An effective Intersection Operations Assessment using SIDRA translates complex traffic behaviour into a set of standardised performance metrics. These indicators are crucial for development applications, as they replace subjective claims like “the traffic is bad” with objective, quantifiable data that councils can assess against established standards. While SIDRA produces extensive reports, a few key performance indicators (KPIs) form the core of any Traffic Impact Assessment.
Level of Service (LoS)
Level of Service (LoS) is a qualitative measure that provides a simple A-F letter grade to describe the operational conditions of an intersection. Think of it as a report card for traffic flow. LoS A represents excellent, free-flowing conditions with minimal delay, while LoS F signifies forced-flow, gridlock, and system failure. From a driver’s perspective, LoS C feels stable, LoS D involves noticeable delays, and LoS E is frustratingly slow. For most development applications, Australian councils require intersections to operate at a LoS of D or better during peak periods.
Degree of Saturation (v/c Ratio)
The Degree of Saturation (often referred to as the v/c ratio) is a critical technical metric that compares the arrival traffic volume (v) to the intersection’s maximum capacity (c). This ratio indicates how close an intersection is to its absolute limit. An analogy is a bucket filling with water; a v/c ratio of 0.85 means the bucket is 85% full. Once the ratio exceeds 1.0, the bucket is overflowing, meaning more cars are arriving than can get through, causing queues to grow rapidly. Councils typically require a v/c ratio to remain below 0.90 to ensure a practical spare capacity.
Average Delay and Queue Length
These two metrics directly measure the real-world impact on road users.
- Average Delay is the average time (in seconds) a vehicle is stopped or slowed while passing through the intersection.
- 95th Percentile Queue is a robust statistical measure of the queue length (in metres). It represents the back-of-queue distance that is not exceeded 95% of the time. This is a critical design parameter, as excessive queue lengths can spill back to block adjacent driveways or upstream intersections, causing wider network disruption.
A thorough Intersection Operations Assessment using SIDRA relies on these outputs to demonstrate a development’s tangible impact.
| Performance Indicator | Description | Typical Acceptable Threshold (Peak Hour) |
|---|---|---|
| Level of Service (LoS) | An A-F grade representing overall operational quality. | LoS D or better. |
| Degree of Saturation (v/c) | The ratio of traffic volume to intersection capacity. | Less than 0.90. |
| 95th Percentile Queue | The practical maximum queue length in metres. | Must not block critical access or upstream intersections. |
The SIDRA Assessment Process: From Traffic Counts to Final Report
A credible Traffic Impact Assessment (TIA) is not a matter of opinion; it is the result of a rigorous, data-driven methodology. The process demonstrates a commitment to accuracy and provides council authorities with the evidence needed for approval. An Intersection Operations Assessment using SIDRA follows a systematic procedure to ensure every variable is accounted for, from existing traffic flows to the predicted impact of a new development. This meticulous approach is a core component of the professional traffic engineering services we provide to secure successful outcomes for our clients.
Step 1: Data Collection and Site Geometry
The foundation of any reliable SIDRA model is accurate, real-world data. Our engineers undertake a thorough data collection phase on-site. This is not a desktop exercise; it requires precise fieldwork to gather essential inputs, including:
- Traffic Surveys: Conducting detailed traffic counts during weekday AM and PM peak hours. These counts capture all road users, including vehicles, public transport, pedestrians, and cyclists.
- Physical Geometry: Measuring existing site conditions such as lane widths, turning radii, approach grades, and the location of signs and line markings.
- Signal Data: Obtaining the current signal phasing and timing plans directly from the relevant road authority (e.g., Transport for NSW, Department of Transport and Main Roads QLD).
Step 2: Building and Calibrating the Model
With all data compiled, we construct a digital model of the intersection network within the SIDRA INTERSECTION software. A critical step is calibration, where the model’s outputs are compared against observed on-site conditions (like queue lengths) to ensure it accurately replicates the existing environment. Once calibrated, we model future scenarios, primarily comparing a ‘Do Nothing’ case (natural traffic growth) against a ‘Do Something’ case that includes the traffic generated by the proposed development.
Step 3: Analysis and Interpretation of Results
The final stage involves running the calibrated model for multiple scenarios, including existing conditions, opening year, and a future design horizon (typically 10 years post-completion). The comprehensive output reports provide key performance indicators such as Level of Service (LoS), average vehicle delay, queue lengths, and degree of saturation. Our analysis identifies potential network issues and allows us to test mitigation measures, such as signal timing adjustments or additional turning lanes, directly within the model. These findings and recommendations are then compiled into a comprehensive TIA report for council submission.
How SIDRA Analysis Strengthens Your Development Application
A comprehensive SIDRA analysis is more than a technical requirement; it is a critical tool for securing your Development Application (DA) approval. It translates complex traffic modelling into a clear, defensible case for your project, proactively addressing council concerns and smoothing the assessment process. By moving beyond assumptions, it provides the solid evidence needed to justify your development’s design and its impact on the local road network.
Providing Objective Evidence to Council
Local councils base their decisions on verifiable data, not speculation. An Intersection Operations Assessment using SIDRA replaces subjective claims with empirical evidence. The analysis delivers industry-standard metrics such as Level of Service (LoS), degree of saturation, and queue lengths. This demonstrates comprehensive due diligence and provides council planners with a clear, accepted framework for their assessment, significantly strengthening the credibility of your application.
Optimising Site Access and Intersection Design
SIDRA analysis allows for the virtual testing of various design options before committing to costly detailed plans. This iterative process is invaluable for optimising site access and functionality. We can model different scenarios to determine:
- The most efficient and safest location for driveways.
- Whether intersection upgrades like roundabouts or traffic signals are warranted.
- The necessary turning lane configurations to accommodate all vehicles, including service and delivery trucks.
This foresight prevents costly redesign requests from council, saving both time and money during the DA process.
Mitigating Impacts and Justifying Your Proposal
A key function of a Traffic Impact Assessment is to quantify the precise impact of development-generated traffic and propose effective mitigation strategies. SIDRA provides the data to prove your solutions work. For example, the analysis can demonstrate exactly how a proposed right-turn lane will improve intersection performance. This data-driven justification is essential for countering objections from council or the public and validating your proposal. For a tailored assessment of your project, contact our engineers directly.
Ultimately, a robust SIDRA analysis de-risks your development project. It is an investment in certainty, providing the technical backing required for a successful DA outcome. Our experienced team utilises detailed SIDRA modelling to build a compelling case for your development, ensuring all traffic-related concerns are addressed with professional rigour.
Expert SIDRA Analysis: The Key to Your Development Approval
As this guide has demonstrated, SIDRA INTERSECTION provides the industry-standard framework for modelling traffic performance. A thorough understanding of its key outputs-from Level of Service (LoS) and delay to queue lengths-is essential for justifying your development’s impact and securing council approval. Ultimately, a professionally executed Intersection Operations Assessment using SIDRA transforms complex traffic data into the clear, quantifiable evidence needed to strengthen your application.
Navigating this technical requirement demands specialist expertise. For over 15 years, ML Traffic Engineers Pty Ltd has provided analysis trusted by developers and councils across Australia. Our commitment is to deliver direct, authoritative results. We guarantee access to our principal engineers on every project, ensuring the consultant who provides your quote is the expert who completes the work, providing unparalleled accountability.
Position your project for a smooth approval process. Get an expert SIDRA analysis for your project. Contact ML Traffic Engineers Pty Ltd for a quote.
Frequently Asked Questions About SIDRA Analysis
Is a SIDRA intersection analysis required for all development applications?
A SIDRA analysis is not mandatory for every development application. Its necessity is determined by the local council or state road authority based on the scale of the proposed development and its anticipated traffic generation. Minor developments with low traffic impact typically do not require it. However, for larger projects like residential apartment buildings, commercial centres, or industrial facilities that significantly affect surrounding road networks, a detailed SIDRA assessment is a standard requirement for gaining approval.
What is the typical cost for a SIDRA operations assessment?
The cost for a SIDRA operations assessment is project-specific. For a single intersection analysis, clients can typically expect costs to range from A$2,000 to A$5,000. This professional fee is influenced by the complexity of the intersection, the number of scenarios to be modelled (e.g., AM and PM peaks, future year forecasts), and the extent of required traffic data collection. A comprehensive assessment involving multiple intersections or a network will have a correspondingly higher fee.
How does SIDRA differ from other traffic software like Vissim or Aimsun?
SIDRA is a micro-analytical traffic modelling tool, ideal for evaluating the capacity and performance of specific intersections or small networks with a high degree of accuracy. In contrast, software like Vissim and Aimsun are micro-simulation platforms. They model the behaviour of individual vehicles across larger, more complex road networks, making them suitable for assessing dynamic conditions like queue spillback, complex weaving sections, and public transport priority systems, which SIDRA is less equipped to handle.
Can SIDRA be used to model and assess pedestrian and cyclist movements?
Yes, SIDRA Intersection is fully capable of modelling pedestrian and cyclist movements. The software calculates specific performance measures for these active transport modes, including delay, Level of Service (LoS), and crossing times at signalised intersections and pedestrian crossings. This capability is essential for a complete Intersection Operations Assessment using SIDRA, ensuring the design adequately provides for the safety and efficiency of all road users, not just vehicles, as required by modern planning guidelines.
How long does a typical SIDRA analysis and reporting process take?
The timeline for a standard SIDRA analysis and report is typically between one to two weeks. This period commences after all necessary inputs, such as traffic survey data and proposed site plans, are received. The process includes model setup, calibration, analysis of various scenarios, and the preparation of a comprehensive technical report detailing the methodology and results. Projects with greater complexity, involving multiple intersections or extensive scenario testing, will require a longer timeframe for completion.
What happens if the SIDRA analysis shows a poor Level of Service (LoS E or F)?
A poor Level of Service (LoS E or F) indicates that the intersection is operating at or over its capacity, resulting in significant delays. When an Intersection Operations Assessment using SIDRA yields these results, it signals to the council that mitigation is required. Our role as traffic engineers is to then propose and model practical solutions. These can include signal phasing adjustments, lane configuration changes, or physical road upgrades to improve performance to an acceptable LoS.
