There is no guarantee that investing billions in infrastructure will help the North of England, the man leading the "Northern Powerhouse" project says.
But former CBI chief John Cridland told the BBC that people should take a "leap of faith" on new roads and railways.
He said he believed reducing journey times between northern cities would improve the economy.
But critics say the money might be better spent on training and skills - or on transport within cities.
Mr Cridland's quango Transport for the North is due to publish its first report soon.
The chancellor's advisory National Infrastructure Commission also will make recommendations on Northern transport.
'Pie in the sky'
The bodies have been considering transport options such as a motorway running under the Peak District from Sheffield to Manchester, or an HS3 rail link between Leeds and Manchester.
But Anne Robinson, from Friends of the Peak District, told BBC News: "These are just pie-in-the-sky schemes. We haven't been given the slightest shred of evidence that they will do any good."
She warned that the motorway scheme - running more than 30 miles underground - would cost a fortune, as well as creating congestion in roads at either end of the tunnel and potentially disrupting the ecology of the Peaks National Park.
Mr Cridland said ambitious infrastructure should be on the agenda: "I'm not claiming there is perfect science here.
"But I am convinced that after decades of under-investment, it's now time to close that investment gap - and it will lead to better travelling experiences and economic growth.
"Transport economics can't always prove this: sometimes, like the Victorian engineers, you have to take a leap of faith."
Ms Robinson said it was foolish to take a leap of faith with billions of public money.
It is likely, though, that both quangos reporting on transport in the north will concentrate their efforts on solutions which bring quick improvement for travellers - like electrifying the Leeds-Manchester route and putting on extra carriages.
Another likely favourite option will be to introduce hard-shoulder running by making all of the M62 a "smart" motorway.
The two bodies may also be anxious to keep hope alive for heroic inter-city infrastructure in the north so people have faith in the regeneration of the region.
There is already a degree of cynicism about ambitious words from Westminster. One Manchester business leader disparaged the term "Northern Powerhouse".
"It's a bit embarrassing isn't it? Frankly it looks like a brand in search of a product," he told me.
Mr Cridland maintains that already the Powerhouse slogan itself has created a sense of excitement and purpose.
The team making key decisions on train operation in the north has been shifted from the south to Leeds, he says - and this is making planners more responsive to local needs.
The big cities of the north are talking to each other, making plans, dreaming they can really breathe new life into the region, Mr Cridland says. Now, he confesses, some infrastructure has to follow.
Follow Roger on Twitter @rharrabin.