On 24/02/2021 20:10, Andrew C wrote:
> Is that true that Melbourne can build tram lines so cheaply? Our lines are rebuilt quickly with massive resources thrown into them, but at what cost? A comparison would be interesting.

I have not seen a costing for Melbourne track re-building, but it may not be a lot different to the Canberra price.
>

> Even allowing for fixed wheel trams, the 1956 St Kilda Road track has been replaced twice in the last twenty years.


St Kilda Rd has very heavy traffic - probably among the busiest in the world.  Melbourne has also had some examples of bad design leading to reduced tramway life:

* Mass concrete produced problems with 'dished joints' excessive wear
around Thermit welds due to lack of resilience in the rail.  See:
https://tdu.to/i/61678
* The "Kirby joint" - designed to eliminate that problem by not using
Thermit welds - proved not be up to the task resulting in large
numbers of broken rail joints.  See attached pic.

It remains to be seen whether Melbourne's current model of using Thermit welds and a more resilient rail foundation survives the test of time.

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> Sydney and to a lesser extant Canberra may well be overengineered, but the tracks do look very solid and will last, as do European tracks that take a long time to replace as I've heard here.

>

The new systems use Thermit welds and put the rail in an insulating boot - which also provides resilience.  The massive concrete foundations in Sydney should last virtuallu forever as, even if the ground beneath moves, they should 'bridge' any subsidence.  Melbourne's lighter foundations won't do that - but given that the foundations have 'settled' for up to 135 years that is not a big problem in most places.

As Matthew says, when the rail (particularly on curves) is due for replacement it will be an interesting exercise.

Mal Rowe - who noticed very badly dished joints in Plenty Rd north of Dundas St yesterday