As peak hour delays leave Australian commuters in limbo, traffic congestion is taking a high economic, social, and environmental toll on the nation.

Australians know the pain of traffic congestion all too well, particularly those who live on the outskirts of the major cities. Commuters driving from Melbourne and Sydney’s outer suburbs to the CBD and back each workday spend around 41 per cent of their commute stuck in traffic. That’s around 77 hours each year, the equivalent of almost two working weeks, according to Infrastructure Partnership Australia’s Travel Time Metric 2020.

What is the impact of traffic congestion? When considering the value of people’s time, road congestion cost the Australian economy $19 billion in 2016, according to Infrastructure Australia’s Urban Transport Crowding and Congestion (2019). Without continued infrastructure investment in our cities, the report suggests this will more than double to $39.8 billion by 2031.

Then there is the environmental impact of millions of cars sitting in traffic. Even when cars are not at a standstill, the slower speeds and stop-and-go conditions of traffic congestion reduces fuel efficiency.


Impacts of reducing travel congestion – Time and environmental benefits

Even a slight decrease in traffic congestion can lead to a significant reduction in travel times, helping to boost the nation’s productivity as people spend less time stuck behind the wheel.

Shorter commute times also improve work life balance and reduce inactivity, in turn delivering physical and mental health benefits while alleviating the social and economic costs of significant public health issues like depression and obesity.

While it comes to the environment, reducing traffic congestion improves fuel efficiency. A large sedan consumes around 1.5 litres of petrol per hour while idling in traffic, meaning those commuters driving from the outskirts of Melbourne and Sydney into the CBD waste around 115 litres each per year.

Along with saving money on petrol bills, those drivers could also reduce their environmental footprint. Each hour a large sedan spends idling in traffic pumps another 1.8 kilograms of CO2 into the atmosphere.

What causes traffic congestion?

A certain level of traffic congestion is inevitable in any large city. Unavoidable traffic incidents, accidents, road works and poor weather can all conspire to extend the time it takes to drive from A to B.

That said, the biggest cause of traffic congestion is a simple matter of supply and demand. Traffic congestion occurs when the volume of traffic travelling through an area exceeds the road infrastructure’s capacity to handle the smooth flow of that traffic.

Factors driving high traffic volumes in Australia include population growth, sprawling cities, employment centralisation and high reliance on cars due to public transport limitations and a car-centric culture.

What are the solutions to reducing traffic congestion?

Increasing road capacity

Australia’s major cities have a history of tackling traffic congestion by building new freeways and expanding old ones. While offering temporary relief, traffic volumes soon increase to fill the extra capacity, an effect known as “induced demand”.

As such, adding lanes to the freeway to combat congestion has been compared to “fighting obesity by letting out your belt” – creating demand which didn’t previously exist.

A 2011 study in The American Economic Review indicates this may be a “fundamental law of road congestion”. Researchers analysed data from the U.S. Highway Performance and Monitoring System from 1983, 1993 and 2003, as well as information on population, employment, geography, transit and political factors.

They determined the number of vehicle-kilometres travelled increases in direct proportion to the available lane-kilometres of roadways. The implication is that building new roads and widening existing ones only results in additional traffic, which continues to rise until peak congestion returns to the previous level.

This clip from satirical Australian TV show Utopia nicely illustrates the short-term ‘sugar hit’ that is trying to solve congestion by simply adding more roads or lanes.

Improving traffic flow

Traffic planners rely on a range of techniques to improve traffic flow in order to reduce congestion.

Ramp signalling in order to drop feed traffic onto freeways during peak times helps traffic flow more smoothly, along with variable speed limits and rapid response to traffic-blocking accidents. Similar strategies can be extended to arterial roads.

Dedicated lanes for vehicles like buses can also, if highly utilised, ease congestion, along with clearways which ensure lanes are free of parked cars during peak hour. Reversible lanes, which flow in different directions at different times of day, can temporarily increase capacity in one direction when required.

Reducing traffic volume – travel demand management

Reducing the number of vehicles on the road would go a long way to easing traffic congestion, as well as helping Australia meet its environmental targets.

One way to reduce traffic volume is to make other modes of transport more attractive. This includes improving public transport’s reach, frequency and reliability, as well as offering park-and-ride services which make it more practical to use public transport for one leg of a journey.. The ideal of improvements in this area is not a better, more frequent timetable, but rather that such services are so frequent that a timetable is superfluous.

Increasing infrastructure support for alternatives like cycling, walking, e-bikes and e-scooters can also encourage people to leave their cars at home. These forms of transport fall under the umbrella of what is called active transport. For some time now, and all across Australia governments are increasing funding into active transport infrastructure, but more evidence and data is needed in order to ascertain the best use incorporation of active transport into the ecosystem. In addition to its contribution to reducing the number of cars on the roads, the other major benefit of active transport is it attendant health benefits.

Another approach is to make driving less attractive. Pricing signals such as road use charges, fuel taxes, and parking fees can encourage drivers to consider other options. These pricing signals can also encourage people to carpool, perhaps with access to high-occupancy vehicle freeway lanes.

It’s important to point out that you don’t have to take that many vehicles off streets to bring about a significant result in easing congestion. The target is to reduce the demand below the ‘tipping point’.

This clip from the YouTube channel of Canada-based Oh the urbanity! goes into more detail on the topic of induced demand, and discusses the differences between induced demand as regards roads, in contrast to induced demand in public transport and active transport.

When you factor in population growth, it’s clear that the mobility model that we have today simply will not work tomorrow. Four billion clean cars on the road are still four billion cars, and a traffic jam with no emissions is still a traffic jam.

Bill Ford – Executive Chairman, Ford Motor Company

Looking at the big picture

Tackling the problem more broadly, societal changes can also reduce peak hour traffic volume and ease congestion.

Rather than sticking to a rigid 9-to-5 schedule, staggering office hours can stagger traffic volumes, resulting in what is known as peak spreading . The rise of the hybrid office arrangement, with many people working from home several days each week, also reduces the number of cars on the road.

When it comes to town planning, efforts to combat urban sprawl by building higher-density housing makes it possible for more people to live closer to good public transport options. Decentralising employment across more satellite hubs, along with planning concepts such as the 15-minute city, can also allow people to work closer to where they live in order to reduce their commute.

Marion Terrill, with bus in the background

Governments in the eastern states are spending enormous sums of money on transport infrastructure. We should use that investment wisely and that means finding a way to encourage people to consider their impact on others when they decide to enter a stream of traffic in peak hour.

Marion Terrill – Transport and Cities Program Director, Grattan Institute

Traffic congestion resources

Here’s a selection of Australian policy and strategy documents on the topic of traffic congestion..

Traffic congestion: Facts and figures

  • The Bureau of Infrastructure, Transport and Regional Economics estimated that congestion cost Australia $16.5 billion in 2015.
  • Without major policy changes, congestion costs are predicted to reach between $27.7 and $37.3 billion by 2030.
  • From January 2013 to 30 June 2018 average driving speeds declined markedly in Australia’s capital cities. Speeds in Sydney and Brisbane fell by 3.6 per cent and 3.7 per cent respectively. In Melbourne, the slow-down was even worse – 8.2 per cent.

Source: Road Congestion in Australia, AAA (2018)

  • Car-travel times due to increasing traffic are to increase by 20 percent in cities such as Melbourne, Perth, Sydney, and Brisbane, among others. In some cases, experts anticipate the increase in travel time to almost double between 2011 and 2031.

Source: Identifying 5 Major Causes of Traffic Congestion in Australia

  • The total costs of road congestion and public transport crowding in Australia’s large cities will be $39.6 billion in 2031. The majority of this cost is attributable to road congestion, $38.8 billion per annum, while public transport crowding makes up $837 million.

Source: Australian Infrastructure Audit 2019 – Transport Chapter

  • About 59% of our population live in our four largest cities, with 40% of Australia’s population living in the two cities of Sydney and Melbourne.
  • In Sydney, weekend transport demand increased by 68% between 2013 and 2016.
  • In 2016, weekend travel time delays across Australia (and New Zealand) accounted for between 15% and 25% of total weekly travel time.

Source: Urban Transport Crowding and Congestion : The Australian Infrastructure Audit 2019 Supplementary report (Infrastructure Australia)

  • Mass public transport in Greater Sydney alone supported more than 750 million trips in 2017–18.

Source: Freight vehicle congestion in Australia’s five major cities (BITRE 2021)

Want to try your hand at traffic management and its repercussions?

Want to see just how easy it is to cause a traffic jam, or, conversely, see how changes to roads, road controls and traffic levels and behaviour can improve flow? Try the link below to a Traffic Simulator. Amongst the things you can manipulate are level of traffic flow, driver following behaviour, lane changing behaviour, level of driver politeness, speed, and more. All the choices you make are then displayed in real-time. Click the button below to have a try a virtual traffic management.


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What is iMOVE doing in the area of traffic congestion?

When it comes to addressing traffic congestion, iMOVE projects are looking at ways to both improve traffic flow and reduce traffic volume.

Optimising the Department of Transport and Main Roads Queensland’s (TMR) motorway control algorithms aims to improve safety and road network efficiency by applying intelligent technologies and advanced control algorithms such as variable speed limits and ramp signalling.

Other traffic flow projects include queue length estimation at signalised intersections and peak hour travel demand calibration.

When it comes to reducing traffic volume, iMove projects include optimising multimodal transport networks, studying innovative transport pricing policies and considering the impact of working from home.

For a look at all of our work in addressing traffic congestion:

What impact iMOVE is having in the area of traffic congestion?

Over and above these individual projects, iMOVE’s work at a more macro level will make a difference to traffic congestion across the country. One area in which we conducted several major pieces of work was in the transport reaction to the COVID pandemic, and the big shift that happened in Working from Home. Particular note should be taken of our overarching report that gathered our findings on this shift, in Prospects for Working from Home: Assessing the evidence.

Other approaches to reducing traffic congestion we’re contributing to are:

Contact iMOVE

There’s still a lot of work to be done in reducing the instances and impacts of traffic congestion on Australian roads.

If you’d like to talk to us about any R&D work in this area, please get in touch with us to start a discussion.

iMOVE traffic congestion projects

iMOVE, along with its partners, is active in carrying out R&D to attack the problem of traffic congestion.

Please find below the three latest traffic congestion projects. Or click to view all iMOVE’s traffic congestion projects.


iMOVE traffic congestion PhD projects

In addition to iMOVE and its partners’ traffic congestion-related projects listed above, as part of our Industry PhD Program businesses, universities and PhD students work on an agreed topic over a three-year period.

These are the three most recent PhD projects that have been undertaken on the topic of traffic congestion. Click to view all iMOVE’s traffic congestion PhD projects.


iMOVE traffic congestion articles

In addition to projects, iMOVE also publishes articles, thoughtpieces, case studies, etc. that cover the many issues and solutions around traffic congestion.

Below are the three most recent articles. Or click to view all iMOVE’s traffic congestion articles.