Tag: Green Belt

All AIs on the Grey Belt

Following on from my experiments using AI to identify and classify small site development opportunities in London’s suburbs, I’ve been deploying the same pattern recognition software on aerial photography to see if it’s possible to categorise, and quantify, how much of London’s green belt has the potential for new homes.

The new government has made much of the potential for so-called “grey belt” to meet the country’s housing need, particularly where this is located close to public transport. The Labour manifesto stated that “the release of lower quality ‘grey belt’ land will be prioritised and we will introduce golden rules’ to ensure development benefits communities and nature.”

This was followed by a consultation version of the National Planning Policy Framework (NPPF) in July 2024, which established a definition for what grey belt is:

“For the purposes of plan-making and decision-making, ‘grey belt’ is defined as land in the green belt comprising Previously Developed Land and any other parcels and/or areas of Green Belt land that make a limited contribution to the five Green Belt purposes (as defined in para 140 of this Framework), but excluding those areas or assets of particular importance listed in footnote 7 of this Framework (other than land designated as Green Belt).”

In her statement to the house which accompanied the launch of the draft NPPF, Angela Rayner said the following:

The Green Belt today accounts for more land in England than land that is developed – around 13 per cent compared to 10 per cent. Yet as many assessments show, large areas of the Green Belt have little ecological value and are inaccessible to the public. Much of this area is better described as ‘grey belt’: land on the edge of existing settlements or roads, and with little aesthetic or environmental value. It is also true that development already happens on the Green Belt, but in a haphazard and non-strategic way, leading to unaffordable houses being built without the amenities that local people need.

There are wildly varying estimates as to how much of the green belt could be considered as “grey”. Property technology outfit LandTech suggested it could be around 0.4%, but CBRE estimated it as 7%. Bearing in mind that England’s metropolitan green belt covers some 16,384 square kilometres (with London’s 5,085sqkm of this), even at 2% this would be enough for more than 1.6m homes. It’s a lot.

Setting aside for one moment the varying definitions of grey belt, I’ve been trying to calculate how much of the green belt is covered by stuff that’s clearly not green. This isn’t necessarily an attempt to find locations to build new homes, but simply an exercise to find the car parks, breaker’s yards, quarries, waste transfer depots and landfill sites that are currently protected from development by virtue of green belt protection.

Counting the Dots

Using GIS mapping I created a grid with intersections every 25m and applied this to the entirety of London’s green belt. In total that’s approximately 8.1 million data points. This is too much to handle in one go, so I divided this down according to planning authority; there’s 72 district councils, unitary authorities and London boroughs who have at least some of the capital’s green belt within them.

The unitary authority of Buckinghamshire has the greatest area of green belt, with 15,630 hectares. This map is taken from article I wrote about the impact of new housing targets on each of England’s planning authorities, and provides a quick overview of the green belt in each:

The smallest is the Royal Borough of Greenwich, which has a tiny area of green belt in its south east corner (so small it can’t be seen in the map below).

At every data point within an authority area I exported a Google satellite image covering an area of 625sqm (i.e. contained within a 25m x 25m tile). I then manually grouped a number of these into categories. Here’s an example of each classification showing the types of images generated:

Armed with a large set of images sorted into folders according to what I could see in each tile, I then trained an AI learning model on the resulting data. Applying this learning model to the remaining images and returning this data to the GIS software, I was able to map the location of every data point and show the distribution of different land types across each authority area.

I started with St Albans City and District Council (SACDC). Below you can see an area in the south of the district, close to the border with Hertsmere. Each coloured circle corresponds to a different designation. The outer colour shows the AI’s best estimate at what’s on the ground, the inner colour are those categories I have determined could be classified as “grey belt”. Tarmac’s Harper Lane asphalt plant appears as a concentration of red and orange blobs; woodland as dark green rings, fields as lighter green, and agriculture in a lighter shade. The grey rings represent buildings, which you can see to the right of the image, with car parks among these in red.

An AI identification of data points in south SACDC showing how the learning model interprets satellite imaging using 25m x 25m tiles.

Although it’s possible to spot some inaccuracies in the classifications, overall this appears to be pretty convincing. One of the issues is that Google’s satellite data varies in resolution across the country, and at which time of the year it was taken. This can lead to agricultural land being misidentified as earthworks, for example, when the picture was taken in winter and the crops harvested. In some remote places the ground is obscured by cloud or vapour trails from passing planes. The use of better aerial photography will help iron out these inconsistencies.

Zooming further into the image you can see numbers appearing within the centre of each dot. This is the “confidence level” that the AI has ascribed to each identification. A score of, say, 60%, means that the AI thinks the tile meets the characteristics of a classification with this degree of confidence. The higher the figure, the greater the chance it’s correct.

This is useful, because the AI also then includes a secondary and tertiary prediction with reducing levels of confidence. Because the tiles cover an area of 625sqm it is likely that they might include different types of ground cover: part car park, part woodland, for example. By multiplying the percentage confidence level by 625 we can get an approximation of how much of the tile is covered by each category. So, a tile that the AI has identified as having a primary classification of “tree cover” with a confidence level of 80% and a secondary classification as “car park”, with 20% confidence, might contain 500sqm of the former and 125sqm of the latter.

While individual data points can display odd results, there are ways to even out the anomalies. Grey belt land uses tend to cover a wider area than just 625sqm, and as can be seen above, the significant opportunities tend to be where a number of these are grouped together. Using a clustering algorithm in GIS we can find those parts of the study area in which many of the positive data points appear. Although these are not particularly useful for analysis, they can help signpost parts of the green belt which are worthy of further investigation.

The map below shows the southeastern corner of Buckinghamshire, a unitary authority. Here I’ve used a clustering algorithm to create a series of circles where groups of grey belt points occur. The grey areas in this image are not within the green belt – everything else is.

Zooming into this area further shows that these clusters are broadly correct. There are some large solar farms in this area, something that’s not found in St Albans (and the dataset on which the learning model was trained), so the AI is incorrectly identifying these as water. A further refinement will be to include a new category for photovoltaic panels. I’ve masked the areas not covered by green belt protection, which are shown in grey.

In the image comparison above you can see the large earthworks (Cemex’s Langley quarry) in the centre of the frame, and the eastern part of Thorney business park to the north. The two areas to the west are Traveller sites, with a solar farm misidentified as water in the bottom right. What this shows is that the use of clustering can help in identifying the areas of potential grey belt. The M25 can be seen running north to south on the right-hand side, and the Elizabeth Line across the centre, broadly parallel to the Grand Union Canal above it. Importantly, Iver Station is just about visible to the left of the intersection between the railway and motorway. Trains stop here every few minutes, so one wonders whether this not make a good location for new homes: the area to the north of the station is clearly a candidate for new development were it not protected by virtue of its green belt designation.

We know that each data point represents an area of 625sqm, so by counting the number of these within each category as determined by the AI, we can quantify the total amount of land occupied by each.

The following table shows the classification of each of the 210,283 points within St Albans District. I’ve highlighted in green those categories of land that I think could be included within a “grey belt” designation.

CategoryData pointsArea (ha)% of TotalGrey Belt? (ha)
Allotments & Garden Centres2,1021311.00%0
Buildings – Commercial 2,0351270.97%0
Buildings – Domestic5,2083262.48%0
Car Parks1,9631230.93%123
Cemeteries202130.10%0
Earthworks1,066670.51%67
Golf Courses8,2175143.91%0
Highway11,6127265.52%0
Open Space – Agriculture65,8464,11531.31%0
Open Space – Fallow Fields11,3497095.40%0
Open Space – General38,7782,42418.44%0
Open Space – Wasteland171110.08%11
Polytunnels & Greenhouses1,325830.63%0
Railways1,205750.57%0
Sewage Farms400.00%0
Sports – Hard Courts4,4932812.14%0
Sports – Pitches & Fields2,8681791.36%0
Tree Cover40,7722,54819.39%0
Water9,6806054.60%0
Yards1,387870.66%87
Total210,28313,143100.00%287
2.18%

Based on these figures we can see that 287 hectares (or 2.18%) of St Alban’s green belt is being classified by the AI as “grey”. This includes earthworks, some of which are likely to have been misidentified due to the similarity between this and dry / fallow fields.

Looking generally at the distribution of these “earthworks” classifications, it appears that around half are likely identified correctly. That leaves around 250 hectares of land with which there’s a high level of certainty over the nature of the surface. That’s just shy of 2% of St Alban’s green belt: or 12,500 homes, if this were built out to a notional capacity of 50dph.

Of course not all of this land will be suitable for development—some is far from public transport or the road network, or otherwise occupied by productive pourposes (some of those concrete batching plants will actually be needed to build these homes!). But even if we generously discount half of the space identified, that still leaves a huge area of grey belt that can be developed for new homes. St Albans’ new five-year housing target, under the new Standard Method, is 7,720 homes. Most will be delivered, one assumes, through urban and suburban intensification. But let it not be argued that the district doesn’t have enough land to deliver these homes.

England’s metropolitan green belt covers an area of 1.64m hectares. Even if just one percent of this falls under the commonly-accepted decision of “grey belt”—car parks, breaker’s yard and landfill—then at over 800,000 homes that’s more than half of the new government’s five-year housing target. This is clearly an opportunity not to be missed.

Right on Target

When the new Labour government’s proposed housing targets were published in July there was some surprise that many planning authorities, particularly urban ones, had seen a significant reduction in the number of homes they were being expected to deliver, and that there was a discernible shift away from the south-east of England to the north-west.

The map below shows the percentage change for each planning authority in England. The authority with the largest reduction is Tower Hamlets, going from 5,190 homes to 2,177 using the proposed Standard Method; a reduction of 58%.

At the other end of the scale, Redcar & Cleveland’s increase of over 1,300% seems large until you realise this is a jump from just 45 homes per annum to 642. That’s just 30% of Tower Hamlet’s new total, despite Redcar & Cleveland having an area more than 11 times greater than the east London borough.

Maybe, then, the changes in numbers expressed as a percentage of previous calculations are not that useful? A different method might be to consider the total number of homes in terms of density. The map below shows what this looks like.

As expected, those areas that you’d assume would have the highest housing demands (in and around England’s major cities) see the greatest number of homes her hectare. Top of the list is London Borough of Kensington & Chelsea, with 3.45 homes per hectare required to meet the new targets. This is an outlier: next on the list is neighbouring City of Westminster, with a target of 1.72 homes per hectare. The top 25 authorities by density are all within London, and the first ranked authority outside the south-east is the City of Bristol, with a target of just 0.28 homes per hectare.

These housing targets have been greeted with considerable uproar, particularly from the anti-development brigade which spuriously claims that this amounts to nothing less than “concreting over the countryside”.

As an example, in an open letter to Angela Rayner published shortly after the targets were revealed, East Hampshire District Council raised the following concerns:

“East Hampshire’s housing targets, as determined by the standard methodology, show we must identify sites for almost 11,000 homes by 2040. 

“But those calculations take no account of the fact that 57 per cent of the district is inside the South Downs National Park, an area where development is restricted. 

“That leaves the remaining 43 per cent of the district to take the lion’s share of development. 

“Inevitably that will put pressure on our highly-prized countryside and our rural towns and villages, which have already seen so much change over the past few years. 

“This is not sustainable development. It is the damage done by a blunt instrument – a planning policy that takes no view of unique local factors.” 

Whilst it’s true that a large proportion of East Hampshire is located within a national park, to suggest that these figures are unachievable is ludicrous. Even building at a relatively low density of 40 homes per hectare, its five-year target of 5,370 would require just a quarter of one percent of its total area to deliver—even if it were to be accommodated in a single location. The reality is, in fact, that most of this will be achieved through the intensification and expansion of existing settlements.

Here’s a map of the district showing the land required to deliver 5,370 homes at 40 dwellings per hectare.

Similar complaints have been heard in Cherwell, which sits to the north of Oxford. Cherwell is similar in size to East Hampshire, albeit without a chunk of national park, so it would take rather a lot of effort to “carpet over” it, as Conservative Councillor Eddie Reeves suggests will happen under the new targets.

To be fair, Cherwell does accommodate some of Oxford’s green belt in the southern region, but other than that is pretty much free from planning constraints. Again, even with a 55% uplift in housing numbers it could find all 5,475 homes using just 0.23% of its land. Suggestions that significant parts of the countryside will be lost to development are very wide of the mark.

Down in Kent, Conservative councillors of Tonbridge & Malling got particularly excited about their new targets, being required to find space for 5,285 homes over the next five years—an increase of just under a third. A large part of the district is within London’s green belt, with some of this coinciding with the Kent Downs AONB. But, as the green belt is no longer a constraint on development, there’s more than enough space for these homes. Hardly the “naked opportunism” that the local Tory Councillor Matt Boughton seems to think it is.

West Berkshire is on a war footing after council leaders described the new targets as a “bombshell“. The CPRE, which can always be relied on to keep a level head in the time of crisis, backed these protestations, claiming that the authority’s new targets of 5,285 homes over five years are “excessive and unsustainable”.

A large chunk of West Berkshire is, to be fair, covered by the North Wessex Downs AONB, and this will certainly prevent housebuilding at scale. But the remaining areas to the southeast, around Newbury and Thatcham, have no such constraints, so there’s no reason why these homes cannot easily be accommodated, particularly as most will be located within the boundaries of existing towns.

It’s tempting to snigger at the hysterical language employed by the many politicians who oppose the building of homes in their local areas, but I genuinely believe that they have a very limited understanding of the scales of land involved. It’s easy to look out of your window at miles of fields and worry that a housebuilder is going to come and plonk a bunch of executive homes in the way of your view, and in some cases that is bound to happen.

But as for “concreting over the countryside”, well, nothing could be further from the truth. The countryside is huge.

We know from previous research that the public has little understanding of how much of the country is built on. A survey in 2018 showed that people tend to think that nearly half of it is. But England’s urban areas take up about 14% of its total area—and that includes urban parks and gardens. The land covered by buildings themselves is even smaller than this. That leaves around 11.5 million hectares of open countryside, most of which is for agriculture.

Now imagine that the government’s 1.5m home target was being located in an entirely new settlement somewhere in the countryside. At a modest density of 40 homes per hectare it would take up an area of 37,500 hectares. That’s just over 2% of the size of England’s green belt. This is what a circle with an area of 37,500 hectares overlaid on a map of England looks like:

Whichever way you look at it, the countryside is safe.

Maps of Every Planning Authority in England

You can view a map of every planning authority in England by choosing from the dropdown list below.

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Britain’s Green Belt is Choking the Economy

I contributed to an article in the Economist newspaper about the state of Britain’s green belt, and the potential to build hundreds of thousands of homes around rural stations.

Sadiq Khan should be bold. He should rethink the green belt

No aspect of planning policy is quite as divisive, or as misunderstood, as the green belt. Covering some 16,000km2, England’s 14 green belts occupy one-eighth of England’s total area (equivalent to three-quarters of the area of Wales, if that’s your preferred unit of measurement).

London’s metropolitan green belt alone stretches from Haslemere in Hampshire to the North Sea—a distance of some 100 miles—and with an area of over half a million hectares is over three times larger than the city itself.

Although its origins precede the Second World War, the green belt was formally established by the Town and Country Planning Act of 1947, which allowed planning authorities to protect open space with this designation. And while the policy has been extremely successful in achieving its original objective of constraining urban expansion, three-quarters of a century on, it’s surely time to reform this anachronistic policy and ensure it meets the needs of the modern world.

Among the marshes of estuary Essex and the undulating hills of Hampshire, there are motorways, waste transfer depots, landfill sites, distribution centres, poultry farms, golf courses and car parks that are all protected from development by the simple virtue of their presence within the green belt. Many areas of otherwise undeveloped space are of limited quality too.

One of the most prominent obstacles to a sensible discussion is the fact that the arguments for and against the green belt have become so utterly polarised. Listening to both sides of the debate, you’d be forgiven for thinking that we face a simple binary choice between the preservation of dwindling landscapes and concreting over every last inch of them. And yet, the green belt has actually grown in recent years. It’s preposterous to claim that it’s under threat.

While we can’t lay the blame for our pitiful national productivity solely at the feet of green-belt policy, it’s clear that our inability to build – whether it’s homes, railways or solar farms – in the places we need, is partly a product of misplaced constraints on development.

Lobby groups like the Campaign for the Protection of Rural England (CPRE) insist that any rethink of the green belt isn’t necessary, but these claims simply don’t stand up to scrutiny. Its latest State of Brownfield report confidently concluded that 1.2 million homes could be built on brownfield land alone, but this is only a quarter of the current shortfall, and certainly insufficient to meet future demands. Furthermore, many of the areas it proposed for new housing aren’t even in the places where need is most acute. I’m not aware of many CPRE members upping sticks from leafy Surrey to the post-industrial wastelands of northern Britain.

There’s a common misconception about the purpose of the green belt in the public sphere, with many mistakenly believing that its purpose is to protect precious rural landscapes. Close to where I live, campaigners against the Cockfosters car park development argued that planning permission should be refused because it would be visible from the green belt, as if the prospect of catching a glimpse of it whilst hurtling along the M25 was a prospect so horrific it didn’t bear thinking about.

In a poorly researched article in the Guardian, Simon Jenkins recently pondered why there wasn’t the same level of protection for the country’s rural parts in the same way that our cities are preserved by Conservation Areas. Any architect or planner could have pointed him towards a whole bunch of protections: AGLV, AONB, Ancient Woodland, SSSI, Ramsar and National Parks, to name a few. Rural areas in fact benefit from far more protections than our towns and cities do, but this is indicative of a wider misunderstanding of planning policy, where green belt is wrongly conflated with other designations that actually do pertain to landscape quality and biodiversity.

It is true that too many open spaces have been relinquished to low-quality, car-dependent sprawl, and nobody – other than the volume housebuilders – wants to see more of that. But, despite what the CPRE claims, we cannot build the homes our country needs on brownfield alone, so some release of open space is inevitable and probably desirable.

There’s a compelling argument that green-belt policy is actually damaging the valuable open spaces that the CPRE is keen to protect. Because building homes is so difficult in places with large areas of green belt, developers target sites beyond it, creating their unsustainable car-dependent sprawl on the outskirts of settlements instead.

Likewise, building new homes on brownfield land far from public transport makes little sense when we could instead cluster them around stations in rural areas, and as an added bonus, give millions of families convenient access to the countryside – something the CPRE claims to support. Not that this should be a free-for-all. Any release of green-belt land for development must be accompanied by robust masterplanning and design codes to ensure that when land is set aside, it is done in a way that is sustainable, accessible, and responsive to local character.

The amount of green belt that would need to be lost to provide a million new homes is so small that it’s little more than a rounding error. Even with modest densities, we’d lose just 1 per cent of the green belt to deliver a million homes. That’s a price worth paying.

Labour’s recent pronouncements in this respect are welcome – if vague . But there are encouraging signs from planning authorities, such as Enfield, that are prepared to tackle this challenge head-on. And emboldened by a lacklustre field of opposition candidates, the mayor of London might revisit his blanket opposition to green-belt release in the next iteration of his city-wide spatial plan. We can but hope.

It’s surely time to set ideology aside and face the fact that an evidence-based review of green-belt policy is long overdue. If we’re to have any chance of facing the challenges of the coming decades, we need to roll up our sleeves and, maybe, loosen our belts.

This article originally appeared in the Architects’ Journal.

Off the Rails

Since its introduction in the post-war period, where it started life as a pragmatic constraint on urban sprawl, the green belt has mutated into an ideological battleground.

Those who consider it to be an unnecessary constraint on progress advocate for its complete removal; others consider it to be sacrosanct, inviolable from development and to be protected at all costs.

The Green Belt Challenge

The reality is—of course—more complex than this, yet it cannot be argued that a blanket ban on any form of development within the green belt, or any amendments to its boundaries, is either pragmatic or reasonable.

It is increasingly apparent that green belt policy needs to be revisited to ensure that it is delivering the best outcomes for citizens. There is not enough land to deliver the homes that we need.

Local planning authorities, who are responsible for managing green belt boundaries, are unlikely to be able to undertake such a task, needing a unified strategy spanning multiple authorities.

Given the strength of feeling and the geography of England’s green belt, this should take the form of a Royal Commission. Only an inquiry with this authority will be able to bring together the relevant parties to properly consider the full range of issues.

As it becomes increasingly difficult to find affordable housing within our cities, those who need to travel frequently to work are forced to live beyond the green belt – in particular, those on lower-paid jobs and the key workers on which cities rely. This adds significant time to the daily commute and acts as a huge drain on productivity and hampers growth.

Station Development

A core objective of green belt policy is to prevent the merging of adjacent settlements. This is sensible. On the other hand, the almost blanket ban on any significant development within designated green belt represents a misunderstanding of its original purpose.

Many cities are surrounded by smaller towns which sit within the green belt: St Albans, Coventry, Guildford, Potters Bar, Macclesfield: these are all towns which are located entirely within the green belts of England’s cities. Green belt inhibits the merging of adjacent settlements, but also prevents the introduction of new settlements within it, even if they possess clear boundaries and sufficient green space to ensure they remain distinct from one another.

England’s train routes tend to radiate from the centre of its cities. Along many of these are stations which benefit from short travel times to urban centres, but which are located entirely within the green belt or open land.

These rural stations provide an obvious opportunity for high-density development close to public transport and within easy reach of places of work.

Multiple studies have shown that these rural stations have the capacity to sustain well over a million new homes. Yet restrictive planning policies, not least green belt protections, prevent this from happening.

10 minutes’ walk equates to around 800m (half a mile). A circle around a single station with a diameter of a mile could, even at modest densities, support up to 15,000 homes. That’s around half of the total number of homes that will be delivered on the Olympic Park.

Unlike Victorian and pre-war England, where new train lines and stations were built so that the land around them could be developed for housing, we would not need to construct new railways for this purpose. They already exist. But the mechanisms for bringing forward such development are subject to considerable planning constraints which often delay projects for years.

Development Corporations

To speed up the delivery of homes in these locations we might adopt a Development Corporation model, with planning powers devolved to a specially incorporated body responsible for delivery. These development corporations would be responsible for bringing forward development in these locations within a defined period – perhaps 10 years – acting as a “master developer”, acquiring land and setting out a masterplan for each location, accompanied by a strict design code informed by the location and local character.

Design codes should set out building heights, street patterns, the quantum of accommodation, orientation and massing, but not favour any particular style: they should promote specificity and a sense of place, rooted in an understanding of context, but this does not mean that they should attempt to ape local vernacular styles.

To coordinate development along transport networks, development corporations could be established following railway lines. This would allow the introduction of social infrastructure, such as schools and healthcare facilities, which need a certain population to support. For example, Meldreth, Foxton and Shepreth stations, which lie on the London to Cambridge line, could together provide homes for over 50,000 people—yet none of these stations is more than 12 minutes apart.

The introduction of new active transport routes, such as cycleways, could also be enabled through the acquisition of land either side of the existing railway, linking these new settlements by sustainable means.

It is not just stations within rural areas that should benefit from development. Transport for London has struggled with securing planning consent for some of its suburban stations.

Therefore, there should be the introduction of new policies to make such development easier. This might take the form of a “presumption in favour” of development close to all stations – including those in urban areas, where densities are significantly higher than those in the surrounding areas.

To mitigate the loss of open space in rural areas, for every hectare taken out of green belt for the purposes of development, an equivalent area could be included within it elsewhere, resulting in no net loss of protected space.

Building within ten minutes’ walk of England’s accessible stations could yield at least 1.2m homes, with the loss of just 680 square kilometres of green belt (in fact it grew by 242 sq km between 2022 and 2023 alone).

There are more reasons to build around stations than not. The mild inconvenience faced by those living in outlying areas who will be unable to use station car parks will be more than mitigated by the huge gains achieved through the provision of new homes, social infrastructure, increased productivity, and economic growth.

This article was first published in the Fabian Society pamphlet “Homes for Britain” in March 2023.

Rural stations are the key to building 1.2m homes in the right places

Perhaps we’ve been desensitised to the stark realities of the housing crisis, with the ‘keep calm and carry on’ attitude of the baby boomer generation (which, we need to remember, lived through very little genuine hardship in the post-war years) prevailing. But in other any functional democracy where 3.6 million young adults remained at home due to generational housing inequality, this would be a national scandal. According to some estimates, we are millions of homes short of where a country with our population should be.

The fact that none of the mainstream parties have yet to articulate a plan to address this crisis is a damning indictment of current political discourse. Not only is this a social failure, it’s an economic one too. Productivity in the UK is woefully low, with young people unable to relocate to where jobs are, or otherwise struggling with extended commutes. Worse still, a generation is delaying starting families as housing costs, employment precarity and overcrowding threaten to detonate a demographic time-bomb which nobody seems willing to defuse.

I live on the northern fringes of London, the final stop before the railway plunges into the capital’s green belt. In less than 30 minutes I can be in central London, on one of six or more trains that run every hour. There are many similar lines that extend out of London, providing convenient access both to the city and countryside for those who live close to them. It’s difficult to think of more appropriate locations for new homes.

Resistance to urban expansion is often (rightly) based on a fear of perpetuating low-density, car-dependent sprawl on the outskirts of our rural towns and villages. So it follows that, in order to create new homes less dependent on private vehicle ownership, we should instead look to optimise development around existing public transport networks. But how many homes might we build? And where?

Using various publicly-accessible data sources, I mapped every train station in England and examined the constraints on development around each. Anywhere at risk of flooding was excluded, as was land within national parks, existing urban areas, or those sites protected by landscape designations because of their quality or scientific interest. Green belt, though, I considered fair game: regardless of what the CPRE claims, it’s increasingly clear that we cannot deliver the homes we need on brownfield alone, and a pragmatic review of green belt policy is long overdue. Drawing an 800m radius around each station (equivalent to a 10 minute walk) and extracting constraints, I arrived at a pleasing 777 stations with development potential.

Not every one is close to a population centre, and some are used by only a handful of passengers each year. As there’s no easy method of measuring current or potential frequency of service, I pegged target densities to passenger annual numbers. Those stations closest to major cities were assigned 75 homes per hectare, those in remote areas much less. But even at modest densities this reveals a huge potential for delivering the new homes we need.

A case in point: Ashwell & Morden sits mid-way between London and Cambridge, with frequent services to both. Yet look at it on Google Maps and you’ll see the station is surrounded by little more than open fields. It’s not even in the green belt of either city. Even at modest densities, this site could accommodate 7,000 homes for some 30,000 people. Development of this scale, supported by a decent masterplan and robust design coding, could provide social infrastructure and sustainable travel for residents. And rolling out a similar approach to the rest of the country could be transformational in providing high-quality homes in sustainable locations such as this.

The familiar complaint from those in comfortable circumstances that we risk ‘concreting over the countryside’ doesn’t stand up to scrutiny when – even with these additional numbers – we’d lose less than 0.4 per cent of England’s rural space in the process (Britain’s roads take up around three times this area).

The coming general election could be a turning point in whether we take genuine steps to address generational inequality, particularly in respect of housing delivery. Building homes around rural stations won’t go the whole way to achieving this but, combined with other bold ideas, it could play a part.

This article was originally published in the Architects’ Journal.