In the late 1890s, American investors forked out cash for the latest sure thing: a 14km toll cycleway between Pasadena and Los Angeles.

It offered two 2m-wide lanes, a maximum grade of 3 per cent and incandescent lighting every 15m. For just 10c, users could pedal back and forth for a whole day.

Then along came the motor car and pedalling to work each day suddenly lost its attraction. The cycleway project died with just 3km of wooden boardwalk completed.

Just over a century later, Auckland property developers Hopper Developments have teamed up with a group of cycling campaigners for a ride down memory lane. They've come up with a plan for a $16 million toll cycleway under Auckland Harbour Bridge.

Now maybe I missed the news bulletin that all the world's oil supplies are interconnected deep underground and are about to spew out into the Gulf of Mexico, and that the world's fuel supplies will soon run out, but I'd have thought building a user-pays cycleway in the city whose love affair with cars matches that of Los Angeles is akin to investing in Greek bonds.

In other words, dead risky. Still it ain't my money, and I hope the Transport Agency makes sure no public money is involved before it gives the project any more encouragement.

The plan is that a trust representing cyclists and walkers will hold - and presumably advance - a half-share in this $16 million project, while Hoppers will own the other 50 per cent.

A $1.95 toll each way will be paid by holders of the proposed Auckland integrated transport smartcard, while casual users will be stung $5 each way.

After 15 years, the cycleway will be handed over to the Transport Agency at no cost - and presumably with no debt. Hopper chairman Leigh Hopper says, "We believe we can attract the institutional funding support needed ..."

Maybe he can, but the bigger question is can he attract enough cyclists to make the long journey and pay the tolls necessary to fund the bridge?

Last November, when the promoters, Getacross, revealed this plan, they wrote of an "estimated demand of 600 to 1500 cyclists per day".

This was certainly more realistic that the 10,000 daily trips - cyclists and pedestrians - they were fantasising about two years ago when badgering the bridge operators to clip on a cycleway. At the time, around 160 cyclists a day were using the free cross-harbour service for bikes.

The latest proposal involves slinging a cycleway pod beneath the eastern clip-on. Transport Agency engineers are evaluating the idea and will respond in "several weeks".

It's hard to believe enough North Shore commuters will abandon their cars, their busway or their ferries for the pleasure of paying a toll and arriving at work hot and sweaty. Enough to fund the repayments. But hey, if no public money is involved, I'm happy to leave it to the market.

Which does raise an issue. If the bridge's nether regions are open for hire, why is the Transport Agency only considering a cycleway. Particularly when no rental is being mentioned.

As a kid, I was always fascinated by pictures of ye olde London Bridge with its shops and other facilities attached to the sides. What's to stop us having shops and restaurants underneath our bridge. You could drop a hook and catch your own dinner.

Alternatively, with Mr Hopper into housing developments alongside canals and harbours and the like, he must have a client base that would be interested in the novelty of living in an apartment over water for a change. The ground rental - or would that be roof rental - would be a tidy little earner for the bridge owners too.

On a more serious note, the cyclists are making a rod for their own backs if the agency accepts their proposal. If there is a genuine need for a cycleway, this is a very bad precedent.

Take, for example, the proposal for a cycleway-footpath across Grafton Gully, from Wellesley St to the Domain. Both the agency and Auckland City Council have failed Aucklanders here and are busy blaming each other for the lack of this obvious link.

Instead of finding the money and getting on with it, they can now point at the harbour bridge toll cycleway and say, "Good idea".