Re: Why Wooden Sleepers are better. Was [NSW] CityRail Delays Friday

[Eccles@ThisNameIsRubbish.co.nz]

On Wed, 29 Mar 2000 23:10:28 GMT, eikkert@my-deja.com wrote:

>But as you did mention, trees take 100 years to grow whereas some of the
>ingredients in concrete may be virtually considered as unsustainable
>resources. Future planning can be done to ensure a sustainable supply of
>wood for railways, 

In NZ man made pinus radiata forests grow in about 30 years.

Tranz Rail uses treated pinus radiata (TPR) sleepers so they must last
longer than the 2 years suggested by someone else in this thread. 

Because TPR sleeper are of limited strength compared with Australian
hardwoods (used in NZ until 1961) they are cut to a larger size.
Hardwood 225 x 110 mm;  TPR 200 x 150 mm.

I suspect that which type of sleeper to use depends on obtaining a
secure supply and the economics. If you have ever prepared a business
case you will know about the dreaded NPV.........