Canberra has long been sold to current and potential residents as a '20-minute city', with daily commutes free of the traffic jams and tolls seen in other Australian capitals.

But with a population projected to grow to more than half-a-million before the end of the decade, the ACT's roads are expected to become more congested.

To help alleviate the pressure on the road network and lower commute times, the ACT government has for years encouraged people to use public transport and urged employers to be flexible about office hours to soften the morning and afternoon peaks.

The car remains most Canberrans' preferred mode of travel, and according to the Climate Council, the city has the lowest use of shared transport of any Australian capital.

The ACT also has more electric vehicles per person than any other jurisdiction. 

Differing promises for roads and public transport have become key points of contention and difference between ACT Labor, the Canberra Liberals and the ACT Greens in the coming territory election.

So how might these approaches impact the congestion on Canberra's roads?

Using public transport out of the question for some Canberrans 

York Stanham, an IT consultant, lives at Evatt in Belconnen and works in Fyshwick. 

He owns an electric vehicle and said catching the bus to-and-from his office is out of the question. 

"It eats up three hours of my day," Mr Stanham said. 

York likes to get to work by 8am – partly to avoid heavy morning traffic — and usually leaves the house at around 7:30am. 

According to Transport Canberra's online journey planner – that same journey by bus would take an hour-and-a-quarter – including a 1 kilometre walk. 

But it's not just the time and the need to leave home nearly an hour earlier that makes catching the bus simply impractical. 

"You can't leave the office easily during the day," Mr Stanham said. 

"And if I had an appointment somewhere I'd need to get a bus there and then get a bus home afterwards – you're looking at getting home at 7 to 8pm."

Mr Stanham said more frequent buses might change his mind but those logistical challenges if he ever needs to make multiple stops mean he'll likely still stick with the car.

"You just turn up and know a bus, a tram or something is coming in the next five to 10 minutes, but here you need to look at the timetable and see there's one at 6:30, the next one's at 7 or 7:30. 

"It kind of locks you in; it's a bit more rigid and it just takes way longer."

Are more roads the solution to congestion?

Few daily commutes are exactly the same, but Mr Stanham's concerns aren't dissimilar from the reasons dozens of Canberrans have given ABC News about why they prefer to drive.

The Climate Council attributes low shared transport usage to a lack of services in Canberra's spread-out suburbs.

Both ACT Labor and the Greens want to continue expanding the existing light rail to Woden, with construction of the first stage of the route to Commonwealth Park underway.

The Canberra Liberals argue extending light rail further south will be too costly and result in longer travel times than by rapid bus — instead promising to build more dedicated bus lanes.

The three parties do agree that more buses are needed, having all promised at least 100 additional vehicles – or more — for the existing bus fleet to deliver more routes and increase the frequency of services.

The ACT government committed to a feasibility study for a Belconnen Transitway in June, and a number of other major road projects are also at various stages of design and construction, including duplications of Gundaroo Drive, William Hovell Drive, and Athllon Drive.

But experts warn additional roads won't necessarily make commutes any quicker.

Brown University economist Matthew Turner and Gilles Duranton from the University of Pennsylvania investigated the effect of lane kilometres on vehicle kilometres travelled in the United States.

In a nutshell, they confirmed what's known as the "fundamental law of highway congestion", which suggests more roads or duplication of roads is unlikely to relieve congestion.

"What the fundamental law of congestion says is that if you add 1 per cent to the lane miles of a big city – so lane miles of limited access highways – then over the course of the next few years you can expect to see about a 1 per cent increase in the total miles driven in that city," Professor Turner said.

The study also found that increasing the availability of public transport also failed to make a dent in congestion.

"If you take people off the roads to ride bus rapid transit or a light rail system, then that's just like freeing up capacity, so you expect the same sort of response," Professor Turner said.

"You're basically making capacity through another mechanism.

Professor Turner said resolving congestion can be much more complex.

"When you build road capacity, you're building more capacity for more people," he said.

"You're getting more people to where they need to go – and that's fine. The same goes for transit.

"Resolving congestion is a whole different thing.

"Congestion just says you've built something useful and too many people are trying to use it."

'It's going to get more crowded'

Roads and public transport aren't the only factors to be considered, with active travel modes like cycling and shared vehicles also in the mix.

In February this year, the ACT government released its Active Travel Plan.

The plan — aimed at guiding infrastructure investment — drew on a 2022 survey that identified at least half of trips in Canberra are around five kilometres or less, with the longest journey generally being to work at around 10 kilometres.

This is where some see densification as key.

The ACT government has established "flexible working hubs" in the city, Dickson, Gungahlin , Woden and Tuggeranong for its public servants.

Labor has promised to build one in Molonglo too, to help reduce the need for at least some people to travel across the city – as well as stimulating growth for local businesses and services.

The Greens have also announced they'll seek more density around existing shops, community facilities and public transport and set city limits to restrict the suburban sprawl.

Professor Turner warns densification can also have pitfalls when it comes to congestion.

"It does reduce total driving, and we estimated if you double the density that people live and work at then you decrease the amount that each person drives by about a twelfth.

"But you pack twice as many people in each space and so you have a lot more travel going on in those little spaces, so getting people closer together might have its own virtues but it's not going to solve your congestion problem."

Professor Turner and his colleague concluded the only proven solution to congestion is charging people a fee to drive into the centre of the city, as seen in London and New York.

None of the parties are proposing congestion charging for the ACT, but it could be food for thought in future, with the population expected to 784,000 by the mid-2060s.