Our nation was built on transportation. It gets us where we need to go, moves goods to market and facilitates economic growth and vitality.

Why, then, should we accept incomplete and unsustainable funding for our highways, bridges, rail and mass transit, especially when U.S. population is projected to reach 400 million by 2050? The need to invest now in transportation is greater than ever.

President Obama's 2014 federal budget proposal floats an aggressive roadmap for restoring our transportation infrastructure to greatness. It's a step in the right direction.

With one in four urban roads in poor condition, according to the American Association of State Highway and Transportation Officials, and one in nine of the nation's bridges rated "structurally deficient" by American Society of Civil Engineers, we cannot afford to allow our infrastructure to continue deteriorating.

But how will we pay for it? The president proposed redirecting defense allocations as overseas operations scale back. Pundits agree Congress won't go for it. Plus, it's a finite commitment of $214 billion over six years.

Instead, America must make sustainable investments for transportation's future, and not simply a transfer from one line item to another. A Federal Highway Administration study shows that each dollar spent on road, highway and bridge improvements results in an average benefit of $5.20 in reduced vehicle maintenance costs, delays, fuel consumption and other impacts as a result of improved traffic flow.

Given the tremendous benefit our transportation system confers on individuals and businesses every day, it seems fair to ask users to help pay to maintain and improve its quality.

One solution lies in the gas tax. For every gallon pumped, you pay a federal tax of 18.4 cents. The tax hasn't changed for 20 years, but its purchasing power only goes half as far. In an attempt to fill the funding void and restore badly deteriorated roads and bridges, at least 17 states are considering a gas tax.

A recent Gallup poll found that two-thirds of drivers would vote against a gas-tax increase. Members of Congress aren't eager to vote for it, either. However, a San Jose State University study found that 58 percent of Americans would support a 10-cent gas tax increase to maintain roadways, and 54 percent would support the tax if it would improve safety. Clearly, Congress and the president could make a case for asking motorists to pay more.

Opponents argue that increased gas tax contributions would diminish over time due to the growing popularity of fuel-efficient cars. If that's the case, another option to consider is taxing vehicle usage as well, perhaps with a "miles traveled tax." Drive more, pay more.

There are still other alternatives: price-managed lanes, for example, require drivers to pay a fee to enjoy an uncongested trip at a guaranteed rate of speed. A new America THINKS poll commissioned by HNTB Corporation found nearly three in four drivers would likely take advantage of this option if given the opportunity.

From 1960 to 1990, the rate of return on investment in highways was a staggering 32 percent. Few investments generate such a return. As such, we must move towards an investment strategy that gives serious consideration to sustainable funding options for surface transportation.

The Obama administration has the right intent in its budget proposal -- preserving and improving transportation systems; facilitating job creation; extending more authority to local governments and increasing accountability.

This is our best chance yet to have a genuine dialogue about what it means to invest in transportation and to pass meaningful legislation that puts the nation's transportation infrastructure on a positive course.

Jim Ely is chairman for toll services for HNTB Corporation, a Kansas City-based civil engineering and architecture design and construction management firm that designs roads, bridges, rail lines and other transportation infrastructure.