SEVEN TRIES BUT STILL NO CLEAR ANSWERS

By Andrew Herington

The LMA were given extra time on Thursday to have another go at trying to explain their traffic model predicting the Hoddle St intersection. The new figures are the seventh set of numbers for Hoddle St/ Alexandra Pde provided by the LMA (CIS Chap7, Question 21, Doc 44, Doc 59, Doc 93, Doc 223, Doc 243).

It is evident to any observer that the results still make little sense and leave a serious mark against the ability of strategic models to accurately predict specific movements (known in the trade as micro-simulation).

The figures make the peculiar claim that 5,000 cars a day will drive west through the tunnel but come back east along Alexandra Pde.

The LMA has avoided talking about this glaring anomaly in their data, but it is there for all to see. There is no rational explanation for this product of computer modelling – but it is a demonstration of the dangers of not testing such predictions against actual origin destination surveys.

They also struggled to explain why, if the traffic movements from Hoddle St south onto the freeway are to drop from 32,000 vehicles per day (vpd) to just 14,000 vpd in 2031, such a massive three lane bridge is required to provide for this when the existing loop has worked successfully for 30 years handling twice the traffic.

Thirdly, it revealed that over 16% of the traffic in the tunnel will be coming to and from Hoddle St and not from the Eastern Freeway at all. These new ramps serve a totally different function from the declared objective of connecting the Eastern Freeway to Citylink and will result in Hoddle St returning to similar levels of usage as now as traffic is attracted into Collingwood – adding to congestion, not relieving.

As Mr Morris explained it “there is no doubt this intersection will be busier in the future than it is now”. Peak hour traffic will operate at Level of Service D – which we have already heard equates to a bumper to bumper crawl. This is not dissimilar to today’s conditions – or for that matter the Burnley tunnel during peak hour.

The assessment committee closely questioned the results and finally got a concession from the LMA that the traffic volume of 72,000 vpd (east of Wellington St) would be more than there are today and the illusion that Alexandra Pde would become a lightly trafficked boulevard and trams would enjoy much more green light time are both completely without foundation.

The LMA retreated to admitting that Alexandra Pde would be worse than today, but better than they calculate it would be in 2031 if the East West Link is not built (88,000 vpd).

However this calculation assumes that there is no upgrade to the DART Bus, the much heralded bus lane in Hoddle St and the Doncaster rail line all don’t exist. Even the PTV includes the Doncaster rail line as being built by 2031.

All of these public transport improvements were excluded from the traffic modelling (see Document 38).

The suggestion that traffic will just keep growing if the East West Link is not built turns reality on its head. The surest way to encourage more traffic is to invest $8 billion to subsidise east west movement of traffic and not invest in any public transport alternatives or traffic management measures (such as increasing the very low occupancy rate of 1.2 people per car on the Eastern Freeway).

The LMA tabled two papers to knock over some straw man arguments of their own construction. A new loop on-ramp was not possible as an alternative to the massive flyover because the design and location they chose involved loss of more historic buildings and expansion of the intersection. This was driven by the design standards they chose which provided a capacity far in excess of what is required (according to their own model)

A number of people have suggested the tunnel portal be covered to Hoddle St with the vent station located between it and the railway line.

The LMA rejected this by presenting a very expensive deep bored tunnel option coming up at the Merri Creek which was subject to flooding and various other alleged problems (not to mention a probable billion dollar price tag).

Their inability to consider simple solutions to the very evident problems with the reference design and the apparent refusal to seriously examine the increasing number of practical alternatives being presented by well-informed community groups is a turning point in this debate.

The CIS clearly fails the test of having considered adequately the “feasible and prudent” alternatives – a point likely to be made repeatedly over the coming weeks.

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