According to U.S. Census Bureau data for 2012, real household income continues to remain depressed at well below mid-2000s levels and hardly any advance beyond mid-1990s. Given that most traffic and revenue forecasts are based on assumptions of growth in personal income it is little wonder traffic is disappointing to tollers and highway infrastructure contractors.

Researchers looking at both toll data and Census figures say that the declines in income are so considerable the economy is probably the dominant factor in the slow but persistent decline in traffic. And yes, there really is a problem when traffic declines...

What does that mean to each of us? It means that projected toll revenues based on higher traffic assumptions, if erroneous, have the potential to leave any number of infrastructure investments, with a shortfall, which, sooner or later, has to be paid.

And where these improvements result from public-private partnerships (P3s), there's a greater likelihood that tolls could climb sooner rather than later.

And we all know who does the paying.

Census data shows the 2012 median household income in 2012-$s was $51.0k actually down a tad on $51.1k of 2011. Both are significantly lower than the post crash years of 2008 ($53.6k) and 2009 ($53.3).

With lesser incomes, less cash on hand, we go out less. That's a no-brainer. 2009 median income was off 5% on peak, mean off 4.5%. But by 2012 median income is off 9% by median and off 6.4% as measured by the mean. All four regjons of America are affected in much the same way - northeast, midwest, south and west, although there is variation state by state.

The declines in income are so considerable the economy is probably the dominant factor in the slow but persistent decline in traffic, Tollroadsnews reports.

But the good news there for motorists paying tolls every day is that, to the extent the change is the economy, a revival of the economy would probably revive traffic too... generating revenue needed for road repair or replacement.

The bad news, however, is that no revival of the economy is clearly in sight, according to Tollroadsnews.com.