Myth: Freeways relieve traffic congestion

Fact: They may provide some short-term relief, but within a short time the extra road capacity generates more traffic than there was before. In the long term freeways just allow congestion to grow further: they don’t reduce it.


The major arteries leading to the very heart of our city are becoming increasingly clogged…. Fortunately, there is a remedy. It will come from having a $1.5 billion by-pass operation that will link and upgrade Melbourne’s three major arteries – the Tullamarine Freeway, the Westgate Freeway and (via the Domain Tunnel) the South Eastern Arterial…. Traffic will again flow freely in and around the Central Activities District, because there will be far less through traffic using our inner city streets. Travel times will be substantially reduced.

—Melbourne City Link Authority advertisement, May 1995

It was hailed as a solution to some of Melbourne’s worst traffic problems. Now, four years after it opened, the CityLink tollway is the focus of a new traffic nightmare – worsening peak-hour congestion on the roads that feed into it.

The Age, 11 November 2004

The Western Ring Road has been an outstanding success since it was built in the 1990s. However, the ring road is now experiencing high levels of congestion, particularly in peak periods, and it is time for its capacity to be significantly enhanced.

—Roads Minister Tim Pallas, Laverton Star, 10 July 2007

Just because you’ve got more traffic doesn’t mean you have congestion.

—Victorian Premier Denis Napthine, ABC News, 9 December 2013

Okay, so 23 lanes didn’t get rid of congestion in Houston. But surely the 24th is the charm.

—Tweet from City Observatory (@CityObs), 19 December 2015

Road planners often promise that freeway building will relieve traffic congestion, especially on the arterial roads that freeways bypass. But the promised relief, if it arrives at all, is usually only temporary.

Official acknowledgement that freeways do not relieve traffic congestion is found in numerous places. There are at least four well-documented recent examples just in Victoria.

First: back in April 2005 VicRoads told a planning panel examining new road construction in central Geelong that the $400 million Geelong Bypass would not, as popularly supposed, relieve traffic congestion on major roads like Latrobe Terrace. Supporting the proposed removal of a heritage overlay to allow a left turn slip lane to be built, VicRoads submitted that

there is likely to be a reduction in traffic volumes of up to 17% in Latrobe Terrace…. immediately on completion of the Geelong Bypass. However the natural growth of traffic (approx 2% per year), as well as a redistribution of traffic from other north/south routes, is expected to result in traffic volumes…. returning to their pre-Bypass volumes in a relatively short period of time.

Second: at around the same time, a report by traffic consultants Parsons Brinkerhoff for the City of Whitehorse predicted that building the Mitcham-Frankston Freeway (MFF, now Eastlink) would do nothing to relieve traffic congestion at the intersection of Springvale Road and Whitehorse Road.

[T]he analysis demonstrates that in future years the existing arrangement and [proposed] intersection treatments result in the Springvale / Whitehorse intersection operating either at or over capacity for traffic scenarios which assume the MFF to be operating (tolled or otherwise). This is an important conclusion as it indicates that the Springvale / Whitehorse intersection will operate overcapacity in future years, even in a traffic scenario which assumes MFF is to be built i.e. solely relying on the traffic redistribution effects of the MFF is unlikely to provide a long term solution to the problems of the Springvale / Whitehorse intersection.

Springvale Road Traffic Improvements Feasibility Project Stage 2: Final Option Review, August 2004, p.25

Third was the East West Link tollway, developed in haste by the short-lived Napthine Government. At the planning panel hearings in March 2014, chief project modeller Michael Veitch conceded the promised congestion relief would be short-lived.

When asked, Mr Veitch admitted traffic volumes would return to Alexandra Pde in the long-term, after the link had been built. He said there was plenty of evidence to show CBD road projects in general “have a relatively short life for the problems they’re solving”. Mr Veitch used the Sydney Harbour Tunnel as an example and said it was full after 13 years and no longer helped reduce traffic congestion.

—“Airport travellers likely to use toll road”, Herald Sun, 5 March 2014

And the fourth, most recent example is the Andrews Government’s North East Link project, claimed to relieve congestion on arterial roads such as Fitzsimons Lane. Yet the government has at the same time continued to plan for more traffic on these arterial roads, not less, with a massive enlargement of the Fitzsimons Lane / Main Road junction in Eltham involving the loss of nearly 1000 trees. Planners told The Age the enlargement was needed despite any congestion relief from the $16 billion North East Link tollway, which they acknowledged would only be temporary.

Major Roads Projects Victoria chief executive Allen Garner said once the North East Link was built in 2027, traffic on Fitzsimons Lane would improve….But Mr Garner said this would only serve as “temporary relief” and congestion would in fact continue to get worse.

“Our traffic modelling shows that without a signalised intersection solution, any temporary congestion relief when North East Link opens in 2027 would soon subside and the current problems would still exist and only get worse. We absolutely need to upgrade Fitzsimons Lane and both projects are needed in their own right. A roundabout will not alleviate the congestion and queuing issues even after North East Link opens,” he said.

—“Road to nowhere? Roundabout revamp could be a waste, say locals”, The Age, 3 March 2021

In the first two cases, subsequent experience has confirmed both the failure of the Geelong Bypass to reduce congestion on Latrobe Terrace, and the failure of EastLink to reduce congestion on Stud Road. Indeed in early 2015, Latrobe Terrace was again nominated as a congestion hotspot; and this was barely five years after the Geelong Bypass opened.

EastLink, too, has borne out earlier admissions that it would not reduce traffic at key congestion hotspots in the eastern suburbs.

EASTLINK will not ease traffic congestion in Whitehorse, with the long-term outlook for roads “hopeless”, a Whitehorse councillor says. Cr Chris Aubrey said the heavy congestion on roads such as Springvale Road in Nunawading would not be eased in the long term by EastLink. “In the first year of the freeway [EastLink], traffic will be reduced by 20 per cent but every year there is a 7 per cent increase in traffic. So in two to three years it will cancel out.”

—“Traffic Trouble”, Whitehorse Weekly, 8 March 2006

The notorious Nunawading intersection is a prime example. Despite repeated calls from the public to fix it there has been continued inaction by the State Government…. Eastlink was never going to solve the problem.

—Peter Daly (RACV), Herald Sun, 15 September 2008

SPRINGVALE Rd is becoming a nightmare again – and toll road bosses at EastLink are crowing. The morning peak along Springvale Rd is now busier than before EastLink was built, despite promises the toll road would solve the traffic problems.

—“Springvale Rd traffic jams as bad as ever”, Herald Sun, 19 August 2010

Had the East West Link been built, it would have repeated the same story. But what has escaped most commentators is that the road lobby themselves had already conceded the inability of these roads to reduce congestion more than temporarily—just not before the decision was made to build them.

The best known and most authoritative official debunking of this myth is still the report of Britain’s Standing Advisory Committee on Trunk Road Assessment (SACTRA) in 1994 – now over two decades old. Quite simply, this states:

Increases in traffic on improved roads are, in general, not offset by equivalent reductions in traffic on unimproved alternative routes.

In Britain this finding has had the status of government policy for two decades – with bipartisan support – meaning that ‘congestion relief’ or ‘travel time savings’ can no longer be used by itself as a justification for building new roads. As a consequence, the motorway-building frenzy of the Thatcher years has (largely) given way in the UK to a new focus on railways and urban public transport networks.

Unfortunately, in Australia the lesson has yet to be learned in official circles. Hence the need for the extensive tour of local and international evidence that follows below.

Why freeways don’t cut traffic

Reason 1: Rearranging traffic jams

The first reason freeways fail to relieve congestion is that freeway traffic still has to go somewhere before and after it uses the freeway. Prior to the construction of Citylink, VicRoads published figures showing that many roads allegedly ‘relieved’ by Citylink would actually be carrying more traffic after Citylink opened than before. Some of this would be through toll avoidance: thus VicRoads predicted that traffic in Mount Alexander Road would more than double, a prediction that has since come to pass. But they also predicted an 80 per cent increase in traffic in Gatehouse Street, a 65 per cent increase in Peel Street, and even an increase on Punt Road at the freeway junction.

The exact same kind of figures emerged when traffic modelling for the East West Link was eventually made public in 2013. The figures, prepared by traffic consultants Veitch Lister and reported in The Age on 9 December 2013, forecast a 69% increase in Eastern Freeway traffic, a 25% increase on Mount Alexander Road, a 41% increase on Earl Street in Kew, and a 35% increase on Hoddle Street, among others. A previous study, conducted in secret by the Department of Transport in 2011 but released under FoI and reported in The Sunday Age on 26 May 2013, had also predicted the East West link would worsen congestion in Hoddle Street.

These increases have nothing to do with people avoiding tolls, but rather the effect of drivers changing routes once the new road is in place. The story has repeated itself elsewhere, such as with Brisbane’s ‘Clem7’ motorway (named after Lord Mayor Clem Jones, who oversaw the shutdown of Brisbane’s tram system in 1969). According to the 2005 Environmental Impact Study, Clem7 should result in an additional 10,300 vehicles a day using busy Lutwyche Road north of the CBD. With Clem7 now operating, Brisbane’s motorists would hardly disagree.

There has been not one traffic engineer who has said that this tunnel will reduce traffic. At best it only displaces traffic. This tunnel is a civil engineer’s wet dream, but it will do nothing to fix traffic issues in Brisbane.

—‘Dangerman’ (online comment), Brisbane Times, 19 March 2010

Reason 2: Roads breed traffic

The second reason is that new roads create new traffic. Thus, even the Vicroads figures above have actually proved to be too low. Indeed, VicRoads and other road lobby consultants have consistently underestimated the traffic consequences of new roads in their traffic studies, such as for the Mulgrave-South Eastern Freeway link in the 1980s, the Eastern Freeway extension and CityLink in the 1990s, and (as the Auditor-General confirmed in 2011) the Hallam and Pakenham Bypasses in the 2000s. This is because their computer models assume that improved roads don’t generate any additional traffic.

This isn’t through lack of understanding. Even car company executives back in the 1920s understood that new roads quickly fill up with new traffic.

Since the advent of the automobile…. the amount of traffic carried by a main thoroughfare seems to be dependent largely upon how many the thoroughfare can carry. Increasing the width of roadway and making possible an additional lane of travel each way will in many cases find the added capacity entirely taken up within a few months, either by diversion from other less favorable routes or by actual increase in the use of cars by those living in and passing through the city in question.

—Alvan Macauley (president, Packard Motor Car Company), in a pamphlet produced in 1925

Evidence denied

As recently as 2006, the Victorian Government touted a consultants’ report claiming the Eastlink tollway would bring $15 billion of economic benefits to the state. Yet the report’s authors admit that the figure was obtained by assuming not one extra car trip would be made as a result of the road being built.

The analysis assumes that the projected demand is from vehicles that would have otherwise used the existing arterial roads, such as Springvale Road and Stud Road. In other words, it assumes that all vehicles travelling on EastLink will incur time savings because they would have otherwise driven on arterial roads. If some of the vehicle journeys are actually ‘induced’ by EastLink, meaning that they would not have occurred if EastLink did not exist, then the time savings counted in our analysis is an overestimate because ‘induced’ vehicle journeys do not result in time savings. It is not possible to obtain an estimate of the number of vehicle journeys induced by EastLink; however, we believe the number would be small.

—Allen Consulting Group, Economic Effects of Eastlink, 2006, page 11

The evidence, both statistical and anecdotal, shows otherwise. Though new roads do temporarily reduce traffic flows on parallel routes, this relief is almost completely wiped out after a few years. Take for example the link between the Mulgrave and South Eastern Freeways built in 1988:

Traffic Flows on Roads Parallel to Monash Freeway
(vehicles per day)
YearWaverley Road
(East Malvern)
High Street
1983 28,000
(Mulgrave – South Eastern link opens)

Source: ARRB Transport Research, Report No. 299, and VicRoads

Three days after [the freeway] opened, I went to check out Waverley Road in the morning peak….it was dead quiet. Not a car hardly. Freeways are great, I concluded. The freeway has removed all this traffic.

Step forward roughly 13 years and we are living elsewhere and I suggested to R that a good way to work was Waverley Road. He said no. It is too busy. Step forward a few months and I had an occasion to see Waverley Road in the morning peak and I was astonished that it was just a long line of stop and start cars.

What changed? The number of cars grew because the ease of travel grew.

—Andrew of the High Riser blog

Has no one asked why the Monash tollway is still 40 minutes outbound in peak hour, just like in the old days of the South-Eastern ‘car park’?

—David Bowker, letter to The Age, 14 June 2005

When they put in the Hallam bypass a few years ago traffic conditions improved noticably for a little while but the volume of traffic went up noticably shortly after and all benefits were obliterated.

—Post to melb.general newsgroup, September 2006

On 27 April I drove from central Dandenong to central Oakleigh, using the Monash Fwy. It took 59 minutes. It’s five lanes, then four and so crowded that I couldn’t get off anywhere to take another route. Not liking that much, next day I drove from the same place to East Oakleigh using Princes Hwy. It took 66 minutes…. They kept us to 80km/h on the Monash for years and years but that was a lot faster than my recent experiences.

—Pat Slattery, letter to RACV RoyalAuto magazine, June 2010

While all that new traffic was flocking on to the Monash Freeway and the roads parallel to it, the road lobby was building Citylink, whose marketing material proclaimed it to be a lasting solution to Melbourne’s traffic problems such as those caused by the ‘dead-ending’ of the Monash Freeway at the city end. Cold reality has proved otherwise: barely five years after Citylink opened in late 2000, the Monash Freeway was called “the worst freeway for traffic delays” by the outgoing CEO of VicRoads. In 2006 the road lobby succeeded in getting more lanes added to this freeway in order to encourage even more traffic, but this didn’t stop the RACV calling the barely-five-year-old Citylink “slow and congested” and a source of “frustrating delays”, which they said could only be fixed by building another freeway – this time through the Yarra Valley.

Meanwhile, the parallel King Street route through the CBD is still classified as a major freight route by the road engineers at Melbourne City Council, and this has been given as a reason why more priority can’t be given to trams on the cross streets. Needless to say, things would be very different if Citylink had really taken all the trucks off King Street, the way it was supposed to do. But while car and truck trips have shifted from King Street to Citylink, just as many entirely new car and truck trips have appeared to take their place.

The story is the same in other Australian capital cities. Take the case of the Sydney Harbour Tunnel, alluded to by the East West Link’s chief modeller above. In 1992 the tunnel opened amid promises that it would fix traffic congestion on the Harbour Bridge forever. The truth is quite different, as the traffic counts show:

Traffic Flows on Sydney Harbour Bridge
(vehicles per day)
YearAverage Flow
(Harbour tunnel opens)

Source: NSW Roads and Traffic Authority, annual average daily traffic data.

After remaining steady over the five-year period from 1987 to 1991, traffic levels both on the bridge and in the tunnel increased throughout the 1990s as Sydney swapped a congested bridge for a congested bridge-and-tunnel. The final cost of the tunnel was $738 million in 1992 dollars; a high price to pay for just a few years of reduced congestion. Traffic levels in the tunnel quickly reached 80,000 per day and persisted at that level, meaning that its effect has been not to reduce congestion but instead to increase the number of cars crossing the harbour by over 30 per cent – despite smaller increases in the size of the central Sydney workforce.

Elsewhere in Sydney, a 2011 analysis by Michelle Zeibots at UTS found that as the M5 southern motorway was constructed in stages between 1992 and 2001, traffic levels in the corridor jumped with each successive stage of construction. Prior to 1992, traffic levels in the area had increased by 1000 to 2000 daily trips each year, roughly reflecting population growth; but in the year the first stage of the M5 opened, traffic grew by 11,200 daily trips, an increase of 15% in regional traffic levels. With the opening of the M5 East tunnel in 2001, traffic into General Holmes Drive jumped by 46,000 trips a day; some 26,000 of these trips were diverted from other roads, but the remaining 20,000 represent entirely new travel.

The weight of evidence has not been lost on commentators in Sydney, even as the road lobby (based in Infrastructure NSW) rolls out fresh proposals for motorway building dominated by the huge ‘WestConnex’ project.

Is a gigantic new motorway connecting the existing parts of the M4 with Port Botany really the transport infrastructure Sydney needs most?

The boosters are already at work to tell us it is. Motorists are promised they will save up to 45 minutes in travel times between western Sydney and the airport or Port Botany. Quite simply, if motorists believe that, they will believe anything.

Time and again the experience of motorways has been an initial reduction in travel times, and then a subsequent rise in the volume of traffic enough to push those travel times back to where they started – $10 billion is an awful lot to pay for a bigger traffic jam.

—Editorial, Sydney Morning Herald, 8 August 2012

What is Plan B when both the M4 and M5 run full in a few years’ time after completion? Except in two notable cases where traffic forecasts were deficient major toll roads have reached practical capacity shortly after opening. Time of day tolling might deter some peak of peak journeys, however many people have little flexibility to alter the time of peak journeys.

—Ron Christie (former CEO, NSW Roads and Traffic Authority), Sydney Morning Herald, 14 October 2012

There is no shortage of similar evidence from Queensland, too. Despite a boom in motorway construction in Brisbane, travel time data collected by Brisbane City Council indicates that motorists’ travel times on parallel arterial roads are no better than before the motorways were built.

Brisbane’s two toll tunnels are not slashing travel times for Brisbane motorists five years after the Clem 7 tunnel opened as promised, Brisbane City Council’s latest travel time statistics shows.

While there have been some suburban improvements, overall Brisbane’s traffic is slower and more congested since Clem 7 (March 2010) and Airport Link opened (2012).

The RACQ’s Michael Roth, executive manager of public policy, said toll tunnels were “not as effective” as Brisbane motorists would have hoped.

—“Brisbane’s toll tunnels fail to cut rising travel times: RACQ“, Brisbane Times, 19 March 2015

In the 1950s, American transport planners used to claim that roads respond to traffic, but don’t cause it. This is nonsense, of course. Road engineers used to be the only business people who thought that if they improved their produce, they wouldn’t get more customers! Government road planners and many politicians are still stuck in the 1950s, denying that road building will produce additional traffic.

It is not surprising that here in Victoria (or elsewhere in Australia) I have never seen or heard of any study that examined the original planning ‘case’ for a new major urban freeway (with all its traffic forecasts and [cost-benefit] calculations) and then tested these forecasts against what happened in practice a few years after the opening of the new road. The answer, of course, would be that the road stimulated new development and car use, and that a widening was on the cards within a few years. Spending billions on roads leaves little in the transport budget for public transport, which reduces its competitiveness, pushing more people into cars they can’t really afford.

—Transport researcher John Grant, 21 September 2011

Gordon Price: I simply ask people: show me the example where this has worked. All I want is for a working example of a city that has built its way out of congestion simply by building more roads, and then is that the place you want to be? I don’t get an answer to A or B.

Peter Mares: You mean, there’s never been a city that’s managed to fix congestion by building more freeways or more roads?

Gordon Price: You might argue that Houston, Texas has. They throw about $1-billion a year into it, they do keep the traffic moving. Do people want to be like Houston? Can you be like Houston? Are you prepared to spend that amount of money and is that really the kind of city that you want in the end? And they have to run as fast as they can just to keep where they are. And they’re looking at transit too!

—Gordon Price (Transport Planner, Vancouver, Canada), ABC radio interview, February 2007

I spent the first 30+ years of my existence in the Houston area. I was in my early-teens during the ‘boomtown’ period in the early-80s, so have watched the city grow…. Houston’s road frenzy has not eased congestion one iota. I have observed this build-up of congestion and sprawl on brand new highways firsthand.

Not only are the GHG emissions bad, [Houston] is also at or near the top in ozone emissions, too. This is thanks to the endless sprawl – the cars, the freeways – and the miserable climate. Not only that, for a while at least, [Houston] was noted as “The Fattest” city in the US. A dubious honor if there ever was one.

—From a blog discussion on Houston

The process of road construction is, of course, the best advertisement for new roads there could possibly be…. As thousands of people inch It is a rare driver who sees those new lanes and thinks that given the projected rate of population growth, freight growth and the lack of investment in public transport those enticing new lanes will soon be as congested as the one they are already in. The illusion that the lane next to you is moving faster is nothing compared to the illusion that the next road we build will be the fast one. But politicians want votes, oppositions promise magic puddings and the road lobby turns our fantasies into their profits.

—Richard Denniss, “Economic road map failure”, Canberra Times, 8 July 2011

(And on the subject of Houston, it appears even the city that spends $1 billion a year marking time on congestion has now passed the point of diminishing returns and reached the point of negative returns. According to statistics collected from 2012 onward, travel times on the colossal Katy Freeway have increased by 30% or more in the three years since it was widened to 23 lanes. As City Observatory remarked on Twitter, perhaps the 24th lane will be the charm.)

Planners come clean: Yes, we’re adding to traffic

Outside the cut-and-thrust of political lobbying, the new traffic created by new roads is tacitly acknowledged in official circles. The Australian Institution of Engineers, the professional body representing road builders, has for many years said in its policy material:

New urban roads always attract traffic….the two main sources are induced traffic (trips that would not otherwise have been made had the road not been built) and diverted traffic (trips that would otherwise have followed some alternative route).

—Australian Institution of Engineers, 1990

New South Wales’ former chief road-builder Ron Christie certainly agrees:

The [Infrastructure NSW] report attempts, but not convincingly, to mount the argument that motorway extensions toward centres of activity do not in themselves attract more private transport. Actual experience is that they do especially if there is a failure to develop a high class public transport alternative.

—Ron Christie (former CEO, NSW Roads and Traffic Authority), Sydney Morning Herald, 16 October 2012

And very occasionally, the new traffic ‘induced’ by new or bigger roads will be acknowledged by the government, sometimes even in the same breath as they call for even more new or bigger roads in order to reduce traffic congestion. Thus, the following statements are juxtaposed on the same page of a State Government brochure, apparently without irony:

Some 48km of the Princes Highway between Melbourne and Geelong has been widened and interchanges have been upgraded… There has been about a 16 per cent increase in the volume of traffic travelling along the upgraded section of Geelong Road.

The Geelong Bypass will provide a 22km freeway-standard road from the Princes Freeway in Corio to the Princes Highway in Waurn Ponds. The bypass will reduce traffic congestion and delays within Geelong’s road network….

Building One Victoria, Victorian Government, 2005, page 20.

Meanwhile, the Eastlink tollway is probably increasing rather than reducing traffic congestion in the City of Manningham, according to road planners’ own predictions:

[N]umber crunchers predict Manningham Rd will be bombarded with up to 20 per cent more traffic when EastLink opens, which could be in June. The sharp rise was forecast by the Southern and Eastern Integrated Transport Authority (SEITA) – the State Government body overseeing EastLink’s delivery.

The authority’s report….also said EastLink’s opening would reduce amenity for residents living on Manningham Rd. Koonung Ward councillor Warren Welsh said Manningham Rd was destined to become “a traffic sewer” if commuters used Manningham as their route to EastLink.

—“Eastlink’s traffic sewer”, Manningham Leader, 15 January 2008

Right on schedule, of course, the same road planners proposed to ‘solve’ this problem with the East West Link and North East Link motorways – in just the same way Eastlink itself was supposed to ‘solve’ congestion problems in the eastern suburbs. Indeed for years, proponents of the westward extension of the Eastern Freeway have tried to have their cake and eat it too in this way, citing as a benefit

Reduced road congestion at the city-end of the Eastern Freeway and the inner north generally, which will be exacerbated in 2008 on completion of the East-link project. The [east-west freeway] would enable easier movement by local traffic, tram, bike and foot and improved amenity between the CBD and the inner northern suburbs.

—VECCI Infrastructure Task Force, November 2005

In other words: yes, building Eastlink will increase congestion, but don’t worry, this new freeway will reduce it again!

The official evidence: Time wasted, not saved

One can also find figures in Vicroads’ own annual report demonstrating that building freeways hasn’t reduced the level of congestion. In fact, the overall level of congestion (as measured by the average delay to traffic) remained steady over the decade 1997-2006 when a record number of major new roads opened – including CityLink, the Western Ring Road, the Hallam Bypass and the Eastern Freeway extension to Mitcham. Reductions in congestion in some locations were evenly balanced by increases in congestion elsewhere. What is even more clear is that freeway-building increased the amount of car travel by 13 per cent over those 10 years, faster than the increase in Victoria’s population (even when offset by a slight decrease in 2006 due to higher petrol prices).

Traffic Levels and Congestion
(At urban monitored locations, all times)
delay (min/km)

Source: VicRoads, Annual Report 2006, page 57.

Transport expert Nicholas Low comments on the lack of evidence for time savings thus:

It is a rather strange fact that despite many billions of dollars being committed to road building on the basis of aggregate time savings, there has not been a single study of whether time has actually been saved as a result of a particular road, or any other form of transport infrastructure, or whether that time is actually spent productively.

—Prof Nicholas Low, University of Melbourne, October 2008

Inspired by this comment, RMIT economist John Odgers in 2009 made an actual study of travel time savings from the Citylink project, and found that the freeway had actually resulted in a travel time dis-saving. As the report concludes:

[T]hese results suggest that… an increase in average travel speeds has not eventuated in Melbourne’s urban road network during the years under review. Indeed, based on the evidence presented and analysed in this paper, one could be led to the conclusion that investments in Melbourne’s urban road network have resulted in more time being used by Melbourne’s motorists rather than less time. On the basis of the assumptions conventionally used to justify road building, major road infrastructure initiatives have resulted in net economic disbenefits…

In closing, perhaps the German word schlimmbesserung—meaning an improvement that makes things worse—is an apt descriptor for the massive program of new road construction that has marked Melbourne’s “solution” to its transport challenges over the last several decades.

—John Odgers, Have all the travel time savings on Melbourne’s road network been achieved? RMIT School of Management, September 2009.

The verdict – that freeways in the long term increase traffic congestion, rather than reducing it – vindicates the conclusion first reached officially in 1994, with the release of the SACTRA report mentioned above. The British Department of Transport’s own expert team concluded that new roads can and do generate traffic.

Travellers must, as a matter of logic, be assumed to respond to reductions in travel time brought about by road improvements by travelling more or further.

—Standing Advisory Committee on Trunk Road Assessment, UK, 1994

Any transport policy must balance the additional economic activity generated by new roads against the self-defeating gridlock that results. [The SACTRA] report, for the first time, takes into account those drivers who switch from one route to another because of a new road, those who change their destination to take advantage of increased accessibility, those who previously used public transport, those whose journeys were caused by a change in land use and those who previously did not travel.

—The Times (Editorial), London, 20th December 1994

An exhaustive US study, covering interstate highways and major arterial roads between 1983 and 2003, reached the same conclusion. In The Fundamental Law of Road Congestion: Evidence from U.S. Cities, authors Gillies Duranton and Matthew Turner concluded that all things being equal, a 10% increase in lane-miles of road caused a 10% increase in vehicle-miles driven.

For interstate highways in the densest parts of metropolitan areas, we find that vehicle kilometers traveled [vkt] increases in exact proportion to highways….

We find that the welfare gains for drivers of building more highways are well below the costs of building these highways. This conclusion follows, not from the high elasticity of vkt to roads, but from the fact that new roads do not reduce the cost of travel sufficiently.

—Duranton and Turner: The Fundamental Law of Road Congestion, 2009

The British and American findings are echoed by Victoria’s own Auditor-General. In 2011, an audit review of State government road projects found they had failed to account for the additional traffic generated by new motorways. In particular, the Auditor-General found that:

  • The Hallam and Pakenham bypasses, costing $165 million and $66 million respectively when they were built in the early 2000s, had failed to reduce congestion in Melbourne’s south-east: instead they had attracted huge amounts of additional traffic. Within three years of opening, the Pakenham bypass was carrying levels of traffic that planners had not expected until 2031.
  • Promised economic benefits of the Peninsula Link motorway have likely been overstated, and negative effects ignored, due to the failure to account for induced demand. It is therefore possible that the entire project was a waste of money – even before the budget blew out from $750 million to $1300 million during construction.
  • The economic case for motorways is further undermined by accounting anomalies that are used to justify so-called Public Private Partnerships (PPPs). Building the Peninsula Link as a PPP may therefore be an even worse waste of money, due to the government artificially inflating the cost of having the road built by the public sector.

The Auditor-General specifically called attention to the failure of local road planners to heed the lessons from Britain, and called for induced demand to be factored into all future planning decisions.

[Road planners] did not adequately assess the traffic induced by these improvements, communicate the risks, or estimate the impact of the economic benefits. These shortcomings create a risk of over-estimating the benefits and giving decision-makers false confidence…. Unlike road authorities in the UK and New Zealand, VicRoads does not have adequate guidelines for forecasting traffic in congested areas.

—Victorian Auditor-General. Management of major road projects, June 2011.

Evidence confirms that this effect actually works the other way as well: closing roads, or reducing road capacity through traffic calming, can actually cause traffic to disappear!

Who’d have guessed you could shut down a third of [Seattle’s] most congested freeway and not paralyze the region in epic traffic jams? Oliver Downs, that’s who…. A few days before the state began what it was calling the most disruptive road project in local history, Downs put out a contrary view. He forecast no extreme clogs anywhere – not on I-5, nor on alternate routes such as Highway 99 or 599. So far he’s been right about that. Then he crazily suggested that one of our chronically jammed roads, the I-405 S-curves in Renton, would actually be better off than normal. Which it has been.

Downs wasn’t dead on. Even his optimistic view was too pessimistic. A stunning 50,000 fewer cars are using northbound I-5 some days. It’s slow going in the work zone. But in many places, driving has been smoother than before….

In 1998, British researchers studied what happened to traffic in more than 100 highway and bridge shutdowns in Europe and the U.S. They found that on average 25 percent of all car trips simply evaporated…. “Drivers are not stupid,” Downs says. “They change schedules. They don’t take some trips, or they delay them. The net effect of all these little decisions can be dramatic.”

—“Math whiz had I-5’s number”, Seattle Times, 22 August 2007

So far Southern California’s fears that shutting down a major highway would result in “Carmageddon” have gone unrealized…. The traffic many thought would be a nightmare has been much lighter than normal as Los Angeles entered the second full day Sunday in the closure of a 10-mile (16-kilometre) stretch of Interstate 405 – one of the country’s busiest highways.

—“Los Angeles bridge project cruising toward finish”, Associated Press, 17 July 2011

New York City closed a mile-long stretch of 14th Street to through traffic, except for buses and trucks, beginning Oct. 3. The 18-month pilot project turned a usually congested corridor into an open road that is speeding up some of the city’s slowest buses by up to 30%, according to city officials.

Transit advocates marveled at how calm 14th Street had become without causing gridlock on surrounding streets. New York City Council Speaker Corey Johnson, a Democrat who had expressed skepticism about the change, said last week that some people were calling it “the miracle on 14th Street,” and that the city should figure out ways of speeding up other bus routes citywide.

—The Wall Street Journal, 17 October 2019

Why we should not be surprised: the Downs-Thomson Paradox

The car works best as a form of travel when few people use it: increasing traffic leads to congestion, making driving less attractive. By contrast, public transport service improves as patronage increases, as frequent services and express runs become more viable. Where public transport and roads are in competition, as in Melbourne, expanding road capacity is a two-way loser. It attracts additional traffic, making road conditions worse, and reduces public transport patronage, making public transport less attractive as well!

Conversely, improving public transport can make life easier for both public transport and road users. Vancouver in Canada has built no freeways for decades, and has invested in public transport instead. In the last decade, average travel times to work have reduced as a result.

This paradox is widely recognised by transport planners overseas, and even has an official name: the Downs-Thomson Paradox. One doesn’t have to look hard to find examples of this principle in action.

Case Study No.1:

The extension of the Eastern Freeway to Springvale Road, opened in 1997, parallels and competes with the Lilydale/Belgrave rail line. In the 1990s the rail line was Melbourne’s busiest, carrying around 15,000 passengers in the morning peak hour, just under half its capacity. Although much wider than the rail line, the Eastern Freeway before it was extended carried only about half this volume (8,000 passengers) but even they strained the road’s capacity, with traffic banked up at the City end of the freeway for three or four kilometres. Now that the freeway has been extended, the traffic jams have grown to twice as long, and commuters who drive into the city from Templestowe regularly complain about the longer delays due to increased traffic!

The further extension of this freeway to Frankston via Eastlink is ultimately expected to dump an extra 28,000 cars a day at the City end – many of which would be escapees from neglected and overcrowded public transport services.

Case Study No.2:

Within weeks of the South Eastern Arterial link opening in 1988, 20% of peak passengers on the Glen Waverley train line shifted to the freeway. Services on the rail line were reduced as a result: in 1987 there were seven peak period expresses on the Glen Waverley line; ten years later there were only two. This has pushed still more passengers onto the freeway, setting up a vicious spiral. Since there are many more rail passengers than freeway users, improvements to the freeway will be cancelled out even if a minority of rail passengers shift their mode of travel. The overall result is that, after the expenditure of hundreds of millions of dollars and the destruction of areas of great scenic beauty, we have worse conditions for both road users and public transport passengers!

Case Study No.3:

With the Environment Effects Statement for the Scoresby Freeway (now Eastlink) in 1997, we finally got official confirmation in Melbourne that public transport can be a more effective treatment for congestion than new freeways. The government’s consultants wrote:

each percentage point increase in PT mode share is estimated to reduce road user costs by about $165 million in 2011….[and there would be] estimated savings in road user costs in 2011 of about $190 million if the Scoresby Freeway is built and public transport mode share is kept unchanged.

Scoresby Transport Corridor EES Working Papers No.2: Addendum, p.24

In other words, the same savings in road user costs would result from increasing public transport mode share by just 1.15 per cent, as from building the freeway. (In the latter case the savings would of course be only short-term, as traffic levels would soon build up until there is just as much congestion as before.) As soon as it was realised that it might damage the case for the Scoresby Freeway, this finding was buried in an obscure supplement to the EES, and no more detailed investigation of any public transport alternative to the freeway ever took place.

Case Study No.4:

In 2005 the road lobby began agitating for a new freeway parallel to the West Gate Bridge, pointing out that between 1994 and 2004 peak-hour travel time over the bridge had more than doubled, from 11 to 25 minutes. But it turns out that this 240% increase in travel time has resulted from only an 18% increase in traffic volume – from 17,600 cars to 21,800 between 6am and 9am. Public transport in the western and northern suburbs has been truly woeful for decades, with trains running only every 20 minutes in peak hour and buses even less often; meanwhile construction of the $630 million Western Ring Road has fed induced traffic onto the bridge. If public transport were improved tomorrow so as to attract one in six journeys away from car travel, traffic on the West Gate Bridge would revert to its relatively free-flowing conditions of 1994. On the other hand, building a second West Gate Bridge would likely just give us two congested bridges in place of one.


In the heyday of freeway building in the 1950s, the well-known architect and urbanist Lewis Mumford warned that trying to cure traffic congestion with more road capacity was like trying to cure obesity by loosening your belt. The result of too much belt-loosening can be seen throughout the USA, where ‘suburban gridlock’ is endemic. With each new road we have imported more of this problem; we should avoid making it any worse.

Congestion, it turns out, is an inevitable consequence when the private sector produces an unlimited number of vehicles and expects the public sector to spend limited resources to build an unlimited amount of space for them to run on.

—Gordon Price, Transport Planner and former City Councillor, Vancouver

Last modified: 4 March 2021