What’s really slowing down the DCO process?

Understanding uncertainty: what Planning Inspectorate DCO casework data can tell us about the journey through application to construction 

The Development Consent Order (DCO) process is more than a regulatory gateway. It is also a period of uncertainty that can materially affect delivery planning. 

Some stages have defined timescales; others vary considerably. Commit resources too early and costs can mount before mobilisation. Plan too cautiously and delivery dates can drift. 

Most infrastructure professionals already know that the DCO process can create uncertainty. What interested me was whether historical data could help us understand it more clearly. 

As a scheduler, I am increasingly asked to look beyond the detailed programme and consider a broader question: when can a project realistically move from consenting into construction, and how much certainty can we place around that transition? 

After learning that the Planning Inspectorate’s DCO Casework Database was available, professional curiosity took over. Could its history tell us anything useful about future applications and help inform a more accurate programme? 

I started testing the data from different angles: did application type, submission year, geography or political context influence where time was gained or lost? 

Of course, every DCO is different, so this is not an attempt to predict an individual application. But project teams often assume that “a DCO takes around X months”. The data lets us ask what circumstances appear to make applications faster, slower or more variable. 

A few points are worth bearing in mind. Across 178 applications that had reached a Secretary of State decision, the average length was 600 days, or around 20 months. Of those, 91 were generating station applications, so the overall figures are heavily influenced by that category. The analysis includes only decided applications. 

Does application type affect the timeline? 

In short, yes – and sometimes significantly. Airport applications took longest to progress through stages without fixed statutory timescales, averaging 34 months, followed by underground gas storage facilities at 30 months.  

The samples are small – three airport and two underground gas storage applications had reached decisions – so these results should be treated cautiously. Even so, they show why a single headline average can be misleading. 

Highways produced a different insight. Their average, at 21 months, was close to the overall figure and the sample was much stronger, with 44 decisions. But looking below that average revealed considerable variation: the A303 Stonehenge project took almost 57 months, while the A160–A180 Port of Immingham Improvement application took just under 13 months. 

Generating station applications, unsurprisingly given their weight in the dataset, sat close to the overall average at around 19 months. 

That spread interested me more than the average itself. For programme planning, “how long does a DCO take?” is too broad a question. We need to understand genuinely comparable projects and the range within them. 

Can wider events be seen in the data? 

The clearest pattern by submission year appeared around the pandemic. Applications submitted between 2018 and 2022 took 27% longer to reach a decision than those submitted in the previous four years. Variability also increased sharply, with the standard deviation of application lengths rising tenfold between 2018 and 2019. 

I would not attribute that entirely to Covid-19. Many applications submitted in 2018 would have been approaching decision as the first lockdown began, but the period also included Brexit, political and policy uncertainty, pressure on public bodies and growing project complexity. 

The data also reflects changing infrastructure priorities. In 2024, 15 generating station applications made up 83% of all applications submitted that year, coinciding with revisions to the energy National Policy Statements and the increased focus on renewable generation. 

Historical data needs context. Pandemic-era cases could make a current programme too cautious, while excluding them could understate what happens when the wider system comes under pressure. 

More encouragingly, recent applications are progressing more quickly and consistently. Despite 2024 and 2025 being the busiest submission years in the dataset, individual stages have shortened considerably from the Covid peak. That may reflect system improvements and greater experience across the departments processing DCO applications. 

Where does uncertainty remain? 

The recommendation-to-decision period stood out as the greatest source of uncertainty. 

Post-Covid applications made under the previous Conservative government spent around 5.5 months at this stage on average, compared with around 3.5 months for those progressing under the current Labour government, against a stated three-month period. 

Applications submitted since mid-2024 are also progressing more quickly and consistently across the stages analysed.  

It would be too simplistic to attribute that solely to a change in government. Recovery from pandemic disruption, departmental capacity, application characteristics and greater experience may all have contributed. 

What the data does show is that programme risk does not end when examination closes. Further information may be requested; unresolved issues may remain live and policy or political considerations can still affect the timing of a decision. 

Does geography make a difference? 

Applications in the South-West took noticeably longer overall, averaging 25 months to decision, compared with just over 21 months in the South-East, the next slowest region. The data also suggests that northern and western applications have progressed more quickly on average than those in the South and East.  

I would be cautious about reading this as a simple regional performance difference. Application types are not distributed evenly, the figures may reflect project complexity, environmental designations, land constraints, political interest or stakeholder opposition. 

The data cannot isolate those factors, but it raises another useful question for programme planning: should we consider comparable applications within the same regional context as well as the same sector? 

What did the analysis tell me? 

The central conclusion is that there is no single DCO timescale. Application type, submission year, political context and geography all appear to influence progress, while some of the greatest variation occurs outside stages governed by clear statutory deadlines. 

Historical data cannot remove uncertainty or predict an individual application. Its value is in challenging assumptions and supporting better-informed conversations about risk, contingency and mobilisation. 

That is the value of this work. It is not about replacing professional judgement with an average but giving project teams better evidence with which to test their assumptions. 

Turning curiosity into better programme decisions 

This analysis began with curiosity about the gap between a DCO application and decision. It has given me more questions to explore rather than one definitive answer – and I think that is useful in itself. 

Progress through the DCO process depends on much more than the formal application. Land, stakeholder engagement, evidence development, consenting strategy, examination preparation and the transition into delivery all shape the timeline. Where those activities are treated separately, dependencies can be missed. 

That is where working with an organisation that spans the full consenting lifecycle can make a material difference. At Ardent, our teams work across those stages, helping projects identify risk earlier, understand the relationships between workstreams and make more informed programme decisions. 

The data can show where time has historically been gained or lost. Combined with practical experience across the consenting lifecycle, it gives projects a stronger basis for managing uncertainty and maintaining progress into construction.