In the contest for Calgary city hall this autumn, one issue makes the headlines time and again: whether taxpayers should fund a $520-million tunnel (the estimate courtesy of the city and Calgary airport authority), underneath the soon-to-be-built new runway at Calgary International Airport.

As most readers know, the new runway necessitates the closure of Barlow Trail at 48th Ave. next spring. The closure will cut off a quick access route for some traffic in northeast Calgary and as a result, it has led to demands for a replacement tunnel to mimic the soon-to-be-closed road.

To judge whether the airport tunnel is a good idea, let's do the math.

Assume the city was to borrow the $520 million and pay it back over 25 years.

At four per cent interest, that's $303 million in debt charges or $823-million in total (in nominal dollars) for the proposed tunnel.

Put another way, the tunnel would require $32.9 million in principal and interest costs annually. That would have to come from taxpayers somewhere, and it doesn't matter if the money comes from Calgary, the province or Ottawa -- there's only one taxpayer.

Another option is to have YYC finance the tunnel and add it onto the existing $22 airport improvement fee. After all, it is argued, the road benefits the airport so why shouldn't passengers pay for the tunnel?

The airport improvement fee brought in $89 million in 2009. If YYC were to finance the tunnel, with another $32.9 million in annual costs, our $22 fee would have to rise by roughly one-third. My guess is few travellers want even higher airport fees that already bulk up final ticket prices.

Another option is for the federal government to cease charging Calgary International Airport an annual rent of almost $21 million. But even in that scenario, the airport fee would still have to rise by another $12 million to make up the difference.

In any event, the airport authority isn't likely to bite on absorbing the tunnel cost, not even if every pro-tunnel politician in the city were elected to council. For one thing, Barlow and the proposed tunnel are on (leased) airport land, so why would YYC offer to foot the bill? If the city wanted it, the city can pay for it. We'll all fly anyway so there is in fact no net benefit to the airport authority from a tunnel, although it would save some airport-bound passengers some driving time.

As for that commuter drive, one morning last week, I duplicated the voyage of Herald columnist Paula Arab, who wrote recently of her circuitous, post-Barlow route to the airport.

Her trek, as with mine, involved driving from the start-point of the intersection of Barlow Trail and McKnight Boulevard heading east, then up Metis Trail, 80th Ave., 36th St. N.E., and then back down to the airport via Country Hills boulevard and Barlow Trail. My travel time was 12 minutes. That was less than Paula's, though I confess to speeding and getting away with it.

Another option (again, from the intersection of McKnight Boulevard and Barlow Trail) is to travel east on McKnight, then north on Deerfoot Trail and use Airport Trail to reach YYC. That took me nine minutes.

In comparison to those trips, the current travel time right from McKnight and Barlow, using Barlow to head north to the airport, is just four minutes.

I grant that my mid-day travel times are shorter when compared to rush hour.

But Calgary's rush-hour traffic jams are not 24-7. So on most days and at most times, the current airport shortcut on Barlow saves between five minutes when compared with my Deerfoot excursion. It saves eight minutes if you take my Metis Trail trek. (Feel free to double those extra minutes in bad though not apocalyptic traffic.)

So starting from Barlow Trail and McKnight Boulevard--which most Calgarians don't -- an airport tunnel would preserve a five-or eight-minute travel advantage, or longer in lousier traffic, all for the princely sum of $823 million.

One last option is, of course, a tolled tunnel built by a private consortium.

But given the multiple entry and exit points to the airport, one doubts they'd take the $823 million risk -- a perfect reminder of why taxpayers shouldn't finance this project either.

There are multiple alternatives for $823 million over 25 years, either not spending the money at all, or road projects in other parts of the city that could shorten everyone's commuter travel time in general, including other priorities for commuters in the northeast.

So is spending $823-million to save five or eight minutes to the airport, or even double those times, and for only a portion of Calgary's commuters, worth it? To ask the question is to see the obvious answer.