More Roads, More Problems: The Mid-Size City Trap and How to Escape It
Key Takeaways
- Growing mid-size cities are caught in a trap: sprawling and building more roads to fix congestion creates more traffic, which creates demand for more roads.
- This cycle is poorly understood by the public and by most politicians.
- Half-measures do not work: cities that invest in public transport while continuing to sprawl and build roads never break their dependence on the car.
- There is often a gap between what governments say in their transport strategies (multimodal) and what they actually spend money on (roads).
- Elections in car-dependent cities tend to reinforce the trap, because politicians go where the votes are, and the votes are for more roads.
- Governance is important. Cities that have a strong, focused political champion tend to find it easier to escape the trap.
- The cities that have successfully reduced car dependency made a clear, sustained choice to prioritise people over cars and stuck to it.
- Changing direction requires a sustained public conversation about trade-offs, not a one-off campaign or a single bold policy announcement.
What Next?
Do your transport investments indicate you are stuck in the mid-size city trap of continuing to build new and bigger roads to try and tackle congestion (or even the large-city trap of fudging and trying to be all things to all modes)?
Introduction
Many growing mid-size cities are caught in a trap. They have traditionally grown by sprawling and investing in road infrastructure. As they grow, this model quickly increases congestion, leading to demands for more and bigger roads, which politicians duly meet. These new roads come at the expense of housing, amenities, and the environment and provide only short-term relief, as they induce more car travel and create more congestion, increasing the demand for more and bigger roads. With each turning of this cycle, the roads become more congested and the city less livable.
The cruel irony is that the trap is well understood by transport and urban planners. Yet despite this, the same mistake keeps getting made. Politicians continue to promise more roads. Voters continue to cheer. And cities continue to pay the price.
This blog explores why the trap is so hard to escape, what happens to cities that fail to break free, and what a genuine alternative could look like. It uses the real mid-size city of Adelaide, Australia, as a case study to bring the problem to life.
Adelaides Context
To understand the mid-size city trap in practice, it helps to look at a real example. Adelaide, the capital of South Australia, is a city that illustrates the challenge clearly, and personally, as a city I have recently moved to.
Adelaide has grown rapidly. At the turn of the millennium, the city had just over 1.1 million people. Today it has around 1.5 million, and it is expected to reach 2 million sometime in the 2040s.
Adelaide is flat, warm, and coastal, with beautiful beaches and a relaxed pace of life. It has consistently ranked among the most livable cities in the world, scoring highly on ease of getting around, access to amenities, and housing affordability.
That picture is changing fast.
House prices have risen 93% over the last five years. The government's response has been to plan over 60,000 new homes, the vast majority on the urban fringe, in new greenfield suburbs that will deepen the city's dependence on the car.
On the roads, the pressure is already showing. Around 20% of the city's jobs are concentrated in the central business district, creating significant congestion during morning and evening peaks.
Governance adds another layer of complexity. Unlike cities with a single powerful Mayor, the kind of political leader who can set a bold direction and be held accountable for it, Adelaide is governed by 15 separate councils, with the big strategic decisions made by the State Government for the whole of South Australia. Adelaide makes up 75-80% of the state's population, but has no dedicated political champion focused solely on the city's future.
The result is a city that has done well in the past, but is increasingly ill-equipped for the pressures of the decades ahead. Adelaide is not yet in crisis. But the trajectory is clear.
Adelaide’s Transport Strategy
Given the pressures Adelaide is facing, you might hope its transport strategy to be bold, urgent and laser-focused on reducing car dependency. In some respects, it tries to be. In practice, it falls well short.
The South Australian Government published its state transport strategy in 2025. There is no strategy specifically for Adelaide, the city that makes up the vast majority of the state's population, it must share a document with the rest of South Australia. That is the first sign that the city's transport future is not being treated with the focus it needs.
The strategy is not without merit. The diagnosis is largely correct. It acknowledges that congestion is getting worse, that building more roads is becoming increasingly difficult and expensive, and that public transport is inadequate. It recognises that transport and land use need to be planned together, and that the city needs to transition away from car dependency. In places, it is surprisingly candid.
On congestion, the strategy notes that without significant changes, the cost to the economy was forecast to rise from $1.44 billion in 2016 to $2.6 billion by 2031. It acknowledges that average peak speeds on key routes have already fallen by almost 10km/h over two decades. It concedes that widening roads is becoming harder and more disruptive, and that alternatives are needed.
On public transport, the picture it paints is stark. Only 3% of Adelaide residents live within a five-minute walk of a frequent, turn-up-and-go service. Around a third have no public transport access within five minutes. For 70% of residents, the wait for a service exceeds 15 minutes. The strategy is clear that this is not good enough.
So far, so promising.
The problem is what comes next, or rather, what does not.
The strategy contains no meaningful targets. There are no commitments to increase public and active transport use, no goals for reducing car dependency and no targets for accessibility. Without targets, there is no accountability.
More damning still are the government's actual spending decisions. At the most recent state budget, every major infrastructure project highlighted by the government was road-based. Not one was primarily aimed at improving public or active transport. The lion's share of transport money is going on new roads, designed to make car trips faster, while buses, bikes and trains receive a fraction of the investment.
The gap between what the strategy says and what the government does could hardly be wider. The strategy calls for a transition away from car dependency. The budget funds the opposite.
This is not unusual. It is, in fact, one of the defining features of the mid-size city trap. Government’s transport strategists diagnose the problem correctly. They write strategies that point in the right direction. And then governments revert to doing what they have always done, building roads, because that is what feels politically safe, and because the public has not yet been brought along on the journey toward a different vision.
Adelaide's transport strategy is a reasonable document, let down by the decisions made around it. The vision is there. The will to act on it is not.
The State Election
If the gap between Adelaide's transport strategy and its spending decisions is frustrating, the state election campaign offers confirmation that things are unlikely to change anytime soon.
The election is being held on 21st March. And if you were hoping for a serious contest of ideas about the city's transport future, you will be disappointed.
The incumbent Labor Government, heavy favourites to win in a landslide, has centred its transport pledges overwhelmingly on road upgrades. The main opposition parties have done the same. The message is consistent: the answer to Adelaide's congestion is more and bigger roads.
This is not entirely surprising. Elections are won and lost on the perceptions of the majority, and the majority of Adelaide's voters still believe that more roads mean less congestion. Politicians are, in this sense, a lagging indicator of public opinion rather than a leading one. They go where the votes are.
But occasionally, an episode cuts through that reveals just how far the political conversation has to travel.
Last year, a debate broke out about garage sizes. As cars have grown physically larger over the decades, a trend known as car bloat, many Adelaide residents can no longer fit their vehicles in their existing garages and carports. The overflow onto streets has made parking harder to find in many neighbourhoods. The Premier's solution was to mandate larger garages in all new residential developments.
It is worth pausing on that for a moment. Faced with a parking problem caused by ever-bigger cars, the government's response was not to question why so many people are so dependent on big cars, or to invest in alternatives. It was to make houses more expensive to build, reducing housing affordability at a time of a housing crisis, in order to accommodate larger cars. The car's place at the centre of Adelaide life, or the right to free parking on the street, was not questioned for a second.
That episode captures the political reality Adelaide faces. The city's elected leaders are not grappling with the mid-size city trap. They are deepening it, one road upgrade and one oversized garage at a time.
This does not mean change is impossible. But it does mean that change is unlikely to come from the top. If Adelaide is going to escape the trap, the impetus will have to come from somewhere else.
Escaping the Mid-Size City Trap
If change is not going to come from state politicians, where will it come from?
This is the central challenge Adelaide faces. And it is worth being honest about how difficult it is. Breaking out of the mid-size city trap is not just a technical problem; it is a political and cultural one. The barriers are not a lack of good ideas. The barriers are public opinion, institutional inertia, and the short-term incentives that shape every election cycle.
Start with public opinion. The vast majority of Adelaide residents still believe that more roads mean less congestion. They have not been exposed to the concept of induced demand. They have not noticed the evidence of what happens to cities that keep building roads as they grow. From where they sit, the formula that worked in the past, build outward, drive everywhere, add lanes when it gets busy, feels like it should keep working. Convincing people otherwise is not a small task. It requires a sustained, honest public conversation about trade-offs that most politicians have no incentive to start.
Then there is the temptation to fudge.
Sydney and Melbourne offer a cautionary tale here. Both cities recognised, at various points, that they needed to invest in alternatives to the car. Both did, up to a point. They built some rail, retained some trams (Melbourne), and added some bike lanes. But they never stopped building roads at the same time. The car remained king (and still is). Buses were left in traffic. Cycling networks were incomplete and often unsafe. Public transport investment never came close to keeping pace with population growth and urban sprawl.
The result, in both cities, has been decades of worsening congestion, a deepening housing crisis, and a steady erosion of livability. The fudge felt politically safe at every step. The cumulative cost has been enormous.
Adelaide does not have to follow that path. But avoiding it will require something that does not come naturally to governments: a clear choice, consistently delivered over many years.
What would that choice look like in practice? It means genuinely prioritising walking, cycling and public transport, not as a complement to the road network. It means building protected bike lanes that form a real network, not painted lines that go nowhere. It means dedicated bus lanes, so that public transport becomes faster and more reliable than sitting in traffic. It means densifying the city around transport corridors rather than continuing to sprawl outward. And it means being honest with the public that some of this will come at the expense of car convenience.
None of this is unique. A few cities around the world have done it. But in most cases, it required political courage, public buy-in, and a willingness to stay the course through the inevitable backlash.
So who could lead this in Adelaide?
The state government, as we have seen, is ill-suited to the task. It must represent a broad constituency across the whole of South Australia, so it is not sufficiently focused on the needs of the city. A city Mayor, with a clear mandate for Adelaide and accountability to its residents, would be better placed, but Adelaide does not have one.
That points toward civic leadership as the most realistic starting point. Organisations like the Committee for Adelaide understand the challenge and have the credibility to convene a serious conversation about the city's future. The task for bodies like this is to move that conversation beyond the professional classes, beyond transport and urban planners and sustainability experts and into mainstream Adelaide thinking.
That means making the case in language that ordinary residents can connect with. Not induced demand and mode share, but: your commute is going to get worse, housing is going to get more expensive, and your city is going to become a worse place to live, unless we make different choices now. It means showing people what a different Adelaide could look like: a city that is more walkable, more affordable, more attractive to young people and businesses, and better placed to compete with Sydney and Melbourne for talent and investment.
Adelaide has genuine advantages that many cities would envy. It is flat. It has a warm climate. It has a quality of life worth protecting. And it is small enough that a shift in public understanding, if it happened, could translate into political pressure relatively quickly.
Adelaide does not need to become Copenhagen or Amsterdam overnight. It needs to start making decisions today that point in a different direction, and to keep making them, consistently, for the decades ahead. That requires a shared vision that a clear majority of people support, and that they will hold politicians accountable for delivering.
Conclusion
Adelaide stands at a crossroads. It can continue down the well-worn path of urban sprawl and road expansion, a path that has already been walked by Sydney and Melbourne, with predictable results: worsening congestion, a housing crisis, and a steady erosion of the livability that has long been Adelaide's calling card. Or it can choose a different future.
The mid-size city trap is not inevitable. Some cities around the world have broken free from car dependency by making bold, sustained choices about how they invest in transport and housing. But doing so requires something that is in short supply in Adelaide right now: an honest public conversation about the trade-offs involved and a shared vision for what the city wants to become.
Governance means that politicians will not lead this change, at least not until public opinion shifts enough to make it politically viable. That means the impetus for change must come from elsewhere: from civic organisations like the Committee for Adelaide, from planners, businesses, and communities who understand what is at stake and are willing to make the case loudly and consistently.
Adelaide could build a genuinely different kind of city, one that is far more liveable and far less dependent on the car. But every new suburb built on the urban fringe, and every new road widened, makes the alternative harder and more expensive to achieve.
Will Adelaide escape the trap? Probably not, but if it does, it will provide a new template for cities around the world to follow.