Common Urban Myths About Transport
Freeways relieve traffic congestion
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.
LIFE WILL CERTAINLY IMPROVE ONCE WE HAVE A TRIPLE BY-PASS
The major arteries leading to the very heart of our city are becoming
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
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
---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
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 three 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
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
The third example is much more recent, and concerns the East West Link
tollway being developed in haste by the 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
have a relatively short life for the problems they're
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
In the first two cases, subsequent experience has confirmed the failure
of the Geelong Bypass to reduce congestion on Latrobe Terrace, and the
failure of EastLink to reduce congestion on Stud Road. We're likely to
see the same story repeat with the East West Link, should it get built.
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.
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
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
---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
However, 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. Quite simply, this states:
Increases in traffic on improved roads are, in general, not offset by
equivalent reductions in traffic on unimproved alternative routes.
Why freeways don't cut traffic
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
Exactly the same kind of figures have also emerged from once-secret traffic
modelling for the East West Link. The figures, prepared by traffic
consultants Veitch Lister and
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. (And this is not the first traffic study to forecast worsening
traffic: a study by the Department of Transport in November 2011 - released
under FoI and reported in The Sunday Age on 26 May 2013 -
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 will 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
---'Dangerman' (online comment), Brisbane Times, 19 March 2010
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
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
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
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,
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)
|Year||Waverley Road||High Street Road|
|(Mulgrave - South Eastern link opens)|
Source: ARRB Transport Research, Report No. 299
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
What changed? The number of cars grew because the ease of travel grew.
---Andrew of the
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
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 hasn't stopped the RACV
calling the barely-five-year-old Citylink
slow and congested and a
frustrating delays, which they say can 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 is 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 Sydney, as the East West Link's chief modeller
conceded above. In 1992 the Sydney Harbour 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)
|(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 no
similar increase 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
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
---Ron Christie (former CEO, NSW Roads and Traffic Authority), Sydney
Morning Herald, 14 October 2012
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 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
---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,
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
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.
Economic road map failure, Canberra
Times, 8 July 2011
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
---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
---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 the road planners:
[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
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
Be prepared for the same road planners to 'solve' this problem with another
freeway - just as Eastlink was supposed to 'solve' congestion problems in
the eastern suburbs. Proponents of the westward
extension of the Eastern Freeway have likewise tried to have their cake
and eat it too, 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 many 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)
Source: VicRoads, Annual Report 2006, page 57.
Transport expert Nicholas Low comments on the lack of evidence for time
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
[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
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
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
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.
The British and American findings are now 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
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,
Research evidence also confirms that this effect 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
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
Why we should not be surprised: the Downs-Thompson 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-Thompson 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
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
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,
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
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© 2010 Public Transport Users Association Inc. (PTUA), Victoria, Australia. ABN 83 801 487 611.
General copying and distribution on a non-commercial basis is permitted subject to proper acknowlegement.
Authorised by Tony Morton, 247 Flinders Lane, Melbourne, for the PTUA
Last modified: 6 March 2014