Submitting a Traffic Impact Assessment report to council should be a straightforward step in your development approval process. In reality, for many applicants, it becomes one of the most frustrating and time-consuming stages of the entire project. Reports get sent back for revision, requests for additional information arrive weeks after submission, and what should have been a formality ends up delaying your project by months.
The good news is that most rejections and revision requests are preventable. Understanding the most common reasons councils push back on TIA submissions — and addressing them before you submit — can make the difference between a smooth approval and a drawn-out back-and-forth that derails your project timeline.
Here is a clear breakdown of the most common reasons traffic impact assessment in Adelaide submissions get rejected or returned for revision, and what you can do about each one.
1. The Scope of the Assessment Doesn’t Match the Project
One of the most frequent causes of rejection is a mismatch between the scope of the assessment and the actual scale or nature of the proposed development. Councils assess a TIA against the specific impacts the development is expected to generate — and if the report doesn’t accurately reflect what is being proposed, the entire document is called into question.
This can happen in several ways. The study area might be too narrow, failing to capture intersections or road segments that will be genuinely affected by the development’s traffic. The assessment might underestimate trip generation by applying incorrect rate categories for the land use. Or the report might simply not address all the modes of transport affected — focusing on vehicle movements while ignoring pedestrian, cyclist, or public transport impacts.
Before submitting, confirm that the study area has been defined in accordance with the relevant guidelines, that trip generation rates reflect the most current published data, and that all affected transport modes have been assessed.
2. Traffic Counts and Data Are Outdated or Insufficient
A traffic assessment report is only as reliable as the data it’s built on. Councils are increasingly scrutinising the currency and quality of traffic count data, and outdated figures are a common trigger for revision requests.
Traffic counts conducted during school holidays, outside of typical peak periods, or on days affected by special events or road closures do not accurately represent normal traffic conditions. Many councils now require counts to be taken during standard school term periods, on typical weekday mornings and afternoons, and within a defined timeframe — often no more than two or three years old at the time of submission.
If your data is stale or was collected under atypical conditions, councils will flag it. The solution is straightforward: ensure traffic surveys are conducted properly, at the right times, and documented clearly within the report to demonstrate their validity.
3. Intersection Analysis Is Incomplete or Incorrectly Modelled
Intersection capacity analysis is often the technical heart of a TIA — and it is also one of the areas most likely to draw scrutiny from council engineers. Common issues include:
- Using incorrect or outdated intersection geometry in the model
- Failing to include all relevant turning movements
- Applying software defaults rather than site-specific parameters
- Not assessing future year scenarios, particularly the design year horizon required by the relevant authority
- Ignoring the cumulative impact of other approved developments in the area that will add to future traffic volumes
Each of these shortcomings can result in a council engineer questioning the validity of the entire analysis. Modelling needs to be technically rigorous, clearly documented, and reflective of actual site conditions and approved future development context.
4. Access and Sight Distance Issues Are Not Properly Addressed
Site access is a critical safety consideration in any development assessment, and inadequate treatment of access arrangements is a reliable source of council concern. Reports that identify access points without properly assessing sight distances, turning radii, or conflict points with existing traffic movements are regularly returned for revision.
Sight distance calculations need to be conducted in accordance with the relevant Australian Standards and DPTI guidelines, taking into account the posted speed limit of the adjacent road, the design vehicle accessing the site, and any obstructions that may affect driver visibility. If sight distances are substandard, the report needs to acknowledge this and propose workable mitigation measures — not gloss over the issue.
Similarly, internal circulation — how vehicles move within the site, where they queue, and how they exit — needs to be clearly demonstrated to avoid conflicts that would push back onto the public road network.
5. The Report Doesn’t Follow Council’s Specific Guidelines
Different authorities have different requirements for how a TIA should be structured, what it must contain, and what standards it must reference. Adelaide City Council, local councils across metropolitan Adelaide, and DPTI each have their own expectations — and a report prepared without reference to the specific guidelines of the relevant authority will often be flagged for non-compliance.
This is a surprisingly common issue, particularly when reports are prepared by practitioners unfamiliar with the specific requirements of a given council. Generic reports that follow a one-size-fits-all structure, reference incorrect standards, or fail to address locally specific concerns are easy for experienced council engineers to identify — and easy to reject on those grounds alone.
Understanding the specific submission requirements of the relevant authority before the report is written — not after — is essential. This is one of the areas where experienced practitioners in traffic engineering in Adelaide add the most value, simply by knowing what each authority expects and structuring the report accordingly from the outset.
6. Mitigation Measures Are Vague or Uncosted
Identifying that a development will generate additional traffic is only part of the job. The more important question is what the applicant proposes to do about it — and councils increasingly expect mitigation measures to be specific, feasible, and supported by evidence.
Vague statements like “intersection upgrades may be required” or “additional investigation is recommended” are not acceptable mitigation responses. Councils want to see clearly defined measures — specific intersection treatments, signage changes, linemarking adjustments, or signal timing modifications — that demonstrably address the identified impacts.
Where infrastructure upgrades are proposed, indicative cost estimates and a clear identification of who is responsible for delivering them (the developer, council, or DPTI) are typically expected. A report that identifies problems without clearly resolving them will be sent back until those gaps are filled.
7. Safety Considerations Are Inadequately Addressed
Road safety is a primary consideration in any development assessment, and councils take it seriously. Reports that focus exclusively on traffic volume and capacity without adequately addressing safety implications — particularly at access points, pedestrian crossings, and school zones — are frequently flagged for revision.
Safety analysis should cover crash history in the study area, identification of existing or likely future conflict points, and a clear assessment of whether the proposed development introduces new safety risks. Where risks are identified, the report needs to demonstrate how they will be mitigated to an acceptable level.
Ignoring or minimising safety considerations doesn’t make them go away — it simply means the council will raise them in their response, adding time and cost to the revision process.
8. The Report Is Poorly Structured or Difficult to Follow
This might seem like a minor issue compared to the technical concerns above, but presentation genuinely matters in a council submission. A report that is poorly structured, difficult to navigate, or inconsistent in its terminology and referencing gives council reviewers less confidence in the underlying technical work — regardless of how sound that work actually is.
Clear executive summaries, well-labelled figures and tables, consistent use of terminology, and a logical flow from background through assessment to conclusions all contribute to a report that council engineers can review efficiently and confidently. Reports that require significant effort to follow often attract more scrutiny, not less.
9. Consultation With the Relevant Authority Didn’t Happen Before Submission
Many experienced practitioners in this field will initiate pre-lodgement consultation with the relevant council or DPTI before formally submitting a TIA. This step — which not all applicants take — allows the scope, methodology, and key assumptions to be agreed upon before the full assessment is undertaken.
Skipping this step means there is a real risk of completing a full report only to find that council has a fundamentally different view of the required scope or methodology. Pre-lodgement consultation doesn’t guarantee approval, but it significantly reduces the likelihood of major revision requests by aligning expectations upfront.
How to Avoid These Issues
The most effective way to avoid TIA rejection is to work with practitioners who have direct, current experience submitting reports to the specific authorities relevant to your project. Understanding what Adelaide councils and DPTI expect, staying current with guideline updates, and building relationships with the engineers who review these reports are all things that come with genuine local expertise — not just technical competence.
Professional traffic management services that include TIA preparation bring a level of process knowledge and local authority familiarity that significantly reduces the risk of avoidable revision requests. When your project timeline depends on a smooth approval process, this experience is worth investing in from the start rather than discovering its value after a rejection has already set your programme back by weeks.
Final Thoughts
Traffic Impact Assessment reports are rejected or returned for revision far more often than they need to be. Outdated data, incomplete intersection analysis, vague mitigation measures, inadequate safety treatment, and failure to follow authority-specific guidelines are all entirely preventable causes of delay — provided the report is prepared carefully, by the right people, with the right local knowledge.
For Adelaide developers, landowners, and project managers, the investment in a well-prepared, thoroughly documented TIA is not just about ticking a box in the approval process. It is about protecting your project timeline, demonstrating genuine responsibility for the traffic impacts your development generates, and building a relationship with the approving authority based on credibility and technical rigour rather than back-and-forth revision requests that serve nobody’s interests.
