Danielle Williamson's opinion piece made the case for a new motorway between Puhoi and Wellsford. Much of her argument centred on the improvements to safety. As many of us know, the road can be dangerous.

About four years ago, I was involved in a car accident on State Highway 1 just outside Wellsford. My mother-in-law, a remarkable woman, was killed and my two children hospitalised.

So, perhaps more than most, I know that State Highway 1 north of Auckland needs upgrading.

But I just can't agree with Transport Minister Mr Joyce's recent announcement to start preparatory work on a new Puhoi to Wellsford motorway.

Nor can I agree that this road is needed above all other priorities where the Government could - and should - be spending money.

Dubbed the Holiday Highway, the project is a colossal waste of $1.69 billion (possibly rising to $2.04 billion) of taxpayer money.

With that sort of money we could transform New Zealand's economy with research and development, provide real backing to our most innovative companies, increase skills, run a train to Auckland airport, build an underground rail link into Auckland's CBD - you name it.

Instead, Mr Joyce is proposing to build a new motorway to run alongside State Highway 1.

Here is what $1.69 billion buys you: motorists will save seven minutes' travel time to Warkworth and eight minutes on to Wellsford.

It promises safer journeys and will ease congestion - particularly as the NZ Transport Agency notes around the "10 major public holiday weekends" such as the one now upon us.

On other days, the number of cars using that road is about equal to a normal day on Auckland's Sandringham Rd.

Yes, it's going to be good for all those people wanting to get to their baches at Omaha Beach on those busy holidays. But the rest of us will pay for it.

And after Wellsford, Northlanders still have to negotiate the winding road around the Brynderwyns.

Does a new motorway make economic sense? It's very marginal.

According to the cost-benefit calculation used by the NZ Transport Agency we get less value back in dollars than what we spend on the motorway.

If the "wider economic benefit" to the region is factored in, one dollar spent will bring $1.10 in return.

That makes it financially viable, but barely. And any economist will tell you that estimating the wider economic benefit is notoriously difficult.

That's why I oppose this road. The economic case simply doesn't stack up.

There is also a broader question whether building more motorways is a good idea. Last year the OECD released a report called "Infrastructure Investment" that studied New Zealand's transport system in comparison with other countries.

It concluded that there is no measurable economic benefit from new motorway construction in New Zealand whereas investment into other types of roading and rail infrastructure does generate growth.

In other words, there are much better ways to spend infrastructure money. This Government should take a look at it.

That's not to say that improvement to SH1 north of Auckland is not needed. I support upgrading SH1.

It does need to be safer. On this point I agree with Danielle Williamson. And while we are at it, the stretch beyond Wellsford needs attention, too.

But upgrading SH1 can be done at a fraction of the cost of an entirely new highway and can be completed much quicker.

That also means a safer road coming on stream earlier than the 10-plus years needed to push through a new motorway.

New Zealand has choices on what sort of future it wants for itself. We also have limited funds and we need to be much more strategic with them.

Let's use those precious resources to lift our prosperity and living standards.

Pouring money into this motorway at this time is a poor choice and frankly, shows poor judgment.

* David Shearer is the MP for Mt Albert, succeeding Helen Clark.