On days when Crowchild Bob sees brake lights by Marda Loop, he braces for the type of stop-and-start traffic that gives commuting a bad name. If he keeps rolling until the Bow River is in sight, he knows he's in for a much better day on the road.

It's a truism of the work-a-day life that commuters understand the ebbs and flows of their daily round trip the way old sailors can read the tides.

Right now, Calgary drivers — at least anecdotally — are noticing something that would have been unthinkable during the extended run of boom-time growth that added tens of thousands of new drivers to the roads every year: traffic seems to be getting better.

Take Crowchild Bob, who's been driving the same route to work for the last 16 years, as an example.

"Three years ago, my commute was taking around 45 minutes in the evening," said Rob Eberhardt, who uses the handle Crowchild Bob as a regular caller to CBC Radio's traffic line. "Now for the most part it's down in the 30-to-35-minute range."

If rush hour traffic in Calgary is indeed improving, the seemingly obvious reason — that a steady diet of layoff announcements in downtown Calgary over the last 18 months is translating into fewer cars on the road — is also the most disheartening.

But is that actually what's going on?

Small numbers, big effect

Drawing a straight line between job losses and what's happening with traffic is tricky. In any city, congestion is affected by a long list of interconnected variables that include population growth, gasoline prices, different transit options and new roads.

The official numbers do indicate that, on balance, getting around the city became easier in the last year, although that doesn't mean traffic improved on every road across the board.

According to city data, the amount that each Calgarian drove last year — a measurement known as annual vehicle kilometres per capita — dropped by 1.7 percent. Another measure tracked by the city, the TomTom traffic index, shows that in 2015, congestion dropped by three per cent.

"In some ways, I find the numbers are fairly small," said Ekke Kok, the City of Calgary's manager of transportation data. "The actual drop in volumes isn't a lot."

Exactly how a decrease in traffic affects a given road can depend on whether a route is close to capacity in the first place. If it's on the cusp of being too full, even a modest dip in the number of vehicles can matter to commuters.

"There are areas that are really sensitive, where taking a few cars off the road would make a disproportionately large difference," agreed Kok, noting that it is reasonable to think that what's happening with the city's economy is also showing up on the roads.

Phantom traffic jams

The theory behind so-called phantom traffic jams, when cars come to a halt for no apparent reason, can help to reconcile anecdotal observations that traffic is getting better with numbers that aren't dramatically different from years past.

When a road is near maximum capacity, like Deerfoot Trail at rush hour, the difference between traffic flowing freely and coming to a halt can be as simple as a single driver touching the brakes at the wrong time.

Even that small act can create a ripple effect that causes the car behind to tap the brakes, then the next, and so on until a few kilometres later vehicles down the line are at a complete stop.

In those cases, removing even a few cars from the equation can make an outsized difference to what happens on the road.

Traffic and the economy

Not every commute, of course, is created equal.

According to Statscan, Calgary's population increase of 30,000 in the last year is more than its estimates for job losses, which are pegged at around 22,000.

The added population combined with the physical size of Calgary's still-expanding boundaries mean the total number of kilometres travelled in the city last year actually went up by 1.2 per cent.

Those numbers mean that for some roads little has changed. Parts of Deerfoot Trail, for instance, are just as busy as they ever were. For others, though, the make-up of the job losses can offer clues into what's happening with commute times.

"What matters for traffic is the spatial distribution of employment, where in the city are these jobs located and where are they being lost?" said Trevor Tombe, an economist at the University of Calgary.

"If most of the losses are in the core downtown area, then this is going to have a larger effect on traffic than if it's more evenly distributed throughout the city."

Putting aside the reasons why traffic is easing up in parts of the city, Crowchild Bob, for one, is enjoying the shorter commute.

When he considers the experience of the evening rush hour on Crowchild a few years ago, he said cars would routinely grind to a halt as early as 33 Avenue. Over the last seven or eight months, though, he says it's become rare to see traffic back up that far.

"Maybe, one day in 10," he said. "It's almost back to the point where it was even 10 years ago."