Antiplanner has some insight into the ongoing presidential primary debate on transportation infrastructure and the federal gas tax, with a good chunk of the sparring (as you know by now) taking place right here in North Carolina:

Back in 1956, Congress dedicated what was then a 1-cent gas tax to the construction of the Interstate Highway System. Engineers estimated that the system would be completed by 1970, so the 1956 bill called for the tax to sunset in that year. Plagued by inflation (and the fact that the gas tax was not indexed to said inflation), the Interstate Highway System was not formally completed until 1991. So Congress got into the habit of reauthorizing the tax every six years.

Now that the highway system is complete, Congress continues to reauthorize. But with no overriding mission, reauthorization has simply become a big pork fest. Earmark money to bridges to nowhere or bridges named after key committee members. Divert 20 percent to transit. Spend even more money on such “transportation” items as turning old train stations into museums or building replicas of slave ships. According to some estimates, Congress has diverted up to 40 percent of highway user fees to non-highway purposes.

Gives you a good idea of how we got where we are.