Presentation to North Sydney community on Westconnex Dr Michelle Zeibots MPIA CMILT
Research Director, UTS Transport Research Centre
1. Induced traffic growth 2. Impact on road network congestion 3. History of F1 motorway 4. Westconnex and the big picture
Induced traffic growth
The following slides provide an example of what transport planners and traffic engineers call induced traffic growthˆ – the addi8onal traffic that is generated by new road or motorway that makes traffic speeds quicker. This example shows the posi8on of the last missing link in the M4 Motorway from Mays Hill to Prospect that was opened to traffic in 1992. AGer opening the combined traffic volumes on the M4 and parallel arterial the Great Western Highway were suddenly higher by almost 20,000 addi8onal vehicle movements on average per day. Where did this addi8onal traffic come from? Further analysis shown that some was traffic that shiGed from road as far away as Windsor and Richmond Roads in the north and Elizabth Drive and Bringelly Road in the south. But even when taking all other possible road op8ons into account, there is s8ll a residual volume of about 11,000 average vehicle movements per day that cannot be accounted for.
M4 Motorway link in Sydney
M4 Mays Hill to Prospect 15 May 1992
M4 Motorway &Great Western Hwy
Annual average daily traffic on M4 Motorway & Great Western Hwy
Opening of motorway section(15 May 1992)
M4 monitoring site
GWH monitoring site
Opening of Mays Hill to Prospect M4 sec8on (15 May 1992)
Induced traffic growth When we examine changes to passenger journey numbers on the parallel Western Sydney Rail Line, we find reduc8ons of about 6,000 journeys on average per day. But this s8ll leaves around 5,000 addi8onal vehicle movements that cannot be accounted for. This appears to be people choosing to make addi8onal trips — induced trips — or travelling to places that are further away than their usual des8na8ons — traffic redistribu5on. On many of these parallel arterial roads traffic volumes returned top what they were before the M4 addi8on with a few years. The pa]ern of responses in this example can be observed in all cases where urban road capaci8es are expanded. It has generally been observed that induced traffic growth rates are higher networks where conges8on levels are highest. It is caused by people wan8ng to take advantage of quicker travel 8mes. In these cases people con8nue to join the network or make more trips un8l travel 8mes return to what they were before the motorway opening where there are no further travel 8me advantages.
Impact on road traffic congestion
This raises the ques8on — what should we do and what effect would building a further motorway extension to the northern beaches achieve? By looking at what happened when the Sydney Harbour Tunnel was opened to traffic in 1992, we can see some similar results to the M4 example — traffic shiGing from the deck of the Harbour Bridge to the new faster route via the Sydney Harbour Tunnel and combined volumes that reveal an increase in traffic known as the ramp up period that is higher than previous volumes. What we can also see is that traffic volumes on the deck of the bridge had stabilised at about 180,000 vehicle movements on average per day from about 1986 un8l 1992. This ‘stable’ volume provides an example of a road opera8ng at full capacity, or what traffic engineers call Level Of Service E. In the following slide you’ll see a table that describes what traffic conges8on levels are like at different volumes ranging from Level Of Service A (which is free and easy) to Level Of Service F (which represents chronic conges8on).
Source: M4 East Environmental Impact Statement: Appendices A–G Volume 2A — Appendix G: traffic and transport assessment. NSW Government, Sydney, p. 1-‐2.
Sydney Harbour Bridge opera8ng at Level Of Service E (1986–1991)
Impact on road traffic congestion There are two significant points that come from this example. (1) This case provides an evidence based example of how traffic engineers assess and measure road traffic conges8on — through Level Of Service grades (A-‐F) based on observa8ons of traffic volume throughputs and limits. (2) Many of the road intersec8ons alongside the newly proposed Westconnex motorway sec8ons are experiencing conges8on at Level Of Service F. The official traffic modeling for the project shows that most of these will con8nue to operate at Level Of Service F aGer Westconnex is brought into opera8on. This raises the ques8on — if official models are showing only minor improvements then why are we building these motorways? Can we really jus8fy spending tens of billions of dollars of public money for li]le or not improvement? Is this why the economic benefit calcula8ons have never been made public? A more construc8ve ques8on to ask is — if we don’t build motorways, what should we build instead and why? What op8ons are there that will genuinely benefit our community?
The role of public transport
Many residents and speakers at this community mee8ng organised through North Sydney Council on Westconnex made the point or raised the ques8on — what can’t we build a train line instead? While I cannot answer ques8ons around the poli8cs, I can answer ques8ons around what the effect on traffic would be if a substan8al public transport line were built — a major train line to serve the sector much like those in all the other sectors of Sydney and soon the North West of Sydney with the opening of the new Metro line. Poten8ally, road traffic speeds would be liGed. How and why this would happen is explained on the next slide. But the important point to make here is that in ci8es all over the world as well as in Sydney, road speeds appear to be largely determined by public transport speeds. This is because the vast majority of people make transport decisions based on whichever op8on is quickest.
The ‘functional balance’ between public & private transport
1. Public transport operates to a fixed speed — a timetable.
2. Roads operate to variable speeds determined by car numbers — congestion.
3. Most people will take whichever transport option is quickest. If public transport is quicker, they'll catch a train or bus, and the number of people won’t change the speed.
4. If driving is quicker, people will use their car. The more who do, the slower the road network becomes.
5. People who shift between modes in pursuit of the quickest option are the reason why public transport speeds determine road speeds.
County of Cumberland Scheme
Business Centres
Special Uses Areas
County Centre
ZONING
Living Areas
Green beltOpen spaceparks etc.
COMMUNICATIONS
National and Regional Roads
Railways
0 1 2 3 4 5 10
Scale of Miles
Bondi
Manly
BotanyBay
Riverstone
Windsor
Broken Bay
Palm Beach
Bulli
Campbelltown
Liverpool
Penrith St Marys
Richmond
Cronulla
Industrial Areas
Rural Areas
Camden
M4
M5
M2M1
M6
F3
Impact of the Northern Beaches Motorway link A motorway to the Northern Beaches is not a new idea. It was first raised in the late 1940s before being incorporated into the legisla8ve plan known as the County of Cumberland Scheme in 1952. In the late 1970s a Commission of Inquiry into the F1 found it should not be built, primarily for reasons to do with induced traffic growth outlined earlier. Back in the 1940 and 50s we didn’t know as much about the real effects of motorway development on urban transport networks. If the Northern Beaches motorway link is built it will funnel more road traffic into the centre of a more extensive congested urban motorway network. In ci8es where motorway networks have been completed so that they are more ‘connected’ like the M25 orbital motorway in London, the nature of conges8on is now worse with the advent of ‘superjams’ — traffic jams that can last for 4, 6 up to 8 hours at a 8me. Condi8ons like this are now more frequent on the network around the Airport where the M5 and other motorways all meet.
Proposed motorway network