Freeways and “as-built” bias: elevated, depressed or something else?

 

Citylift proposition

Citylift’s proposition for the Foreshore – a built earthwork ‘berm’ to replace the existing foreshore freeways, with buildings elevated, and cars hidden – looks radical at first glance. We must be careful, though, not to suppose that just because something (elevated freeway structures) are familiar, they are necessarily best. A rummage through the engineering reports of the 1960s, when the built schemes were under design scrutiny, tells interesting stories of early design decisions and the rationales behind them.

The much mooted underground tunneling of the freeway scheme was actually considered in the 1960s, but rejected on cost grounds. Professor Holford, one of the assessors on the Shand Committee which deliberated on the scheme at the time estimated R3,500,00 for a depressed (underground level but open) scheme and R1,600,000 for an elevated Table Bay Boulevard scheme. Quite how this elevation should take place, though, was undecided until the late 1960s. The 1968 engineer’s design report estimated that elevated structures (as we see them today) would be 8% more expensive than an earth retaining wall…but the engineers argued they would be justified on aesthetic grounds, and on the ability to retain parking underneath. The costs subsequently escalated well beyond these early estimates.

We need to beware of bias towards what is familiar and judge each scheme on its merits today.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: