In late April, Secretary of Transportation Anthony Foxx presented Congress with the Obama administration’s four year, $302 billion transportation GROW AMERICA Act, ostensibly to address the substantial shortfall in the Highway Trust Fund and provide an additional $87 billion to address the backlog of structurally deficient bridges and aging transit systems across the country. As with most things in Washington, D.C., the devil is in the details.

Buried within the 350-page bill are some troubling provisions. Among these is one that would reverse the decades-long prohibition on tolling existing interstate highways. The transportation bill justifies this elimination as “providing States greater flexibility to use tolling as a revenue source for needed reconstruction activities on all components of their highway systems.”

However, this isn’t the whole story. The new tolls that would be imposed on interstates we now use freely could be diverted “to be used for costs necessary for improving public transit service” and “to mitigate adverse impacts related to the tolling facility.” This is a gimmick. It allows states to impose a toll on existing interstates that have been built using other revenue sources, such as the gas tax, and then divert the toll revenues to be spent on mass transit or other purposes. This kind of toll proposal sounds more like a tax and less like a “user fee.”

Beyond this shuffling of funds, tolling an existing interstate for any reason is difficult to justify on principle. Interstate construction and maintenance has been funded through fuel taxes since the system’s inception in 1956. Requiring drivers to pay a new toll in addition to a gas tax is paying for the same road twice.

Tolling existing interstates for road revenue is not a new idea. Congress passed the Interstate System Reconstruction and Rehabilitation Pilot Program in 1988, creating a pilot program for designated states to toll existing interstates. To date, none have successfully done so, largely due to the recognition of tolling’s negative effects and significant public opposition. Most recently, both Virginia and North Carolina proposals to toll Interstate 95 were shelved and Missouri I-70 tolls never got off the ground. The lesson from these ill-fated pilot projects is clear — tolling existing interstates is a bad idea.

There are other equally compelling reasons to reject this new tolling initiative. Tolls can cause delays and make roadways less safe by disrupting traffic patterns around a toll facility. Moreover, tolls cause traffic diversion that creates congestion on local and secondary roads near toll facilities. The congestion delays response times for emergency personnel who rely on these secondary routes. A recent study on the effects of tolls in North Carolina predicted that tolls would divert more than one-third of traffic to alternate routes, contributing to delays, traffic accidents and wear and tear on secondary roads not build to handle high traffic.

Tolls on existing interstates are bad for the economy. Tolls increase the costs of shipping goods and services and make more expensive the price we all pay at the grocery store and at the mall. Daily commute tolls take a bite out of a worker’s take home pay. And, tolls are particularly unfair to low-income and elderly Americans living on fixed incomes who must pay a higher percentage of their income to access tolled interstates.

The Obama administration’s plan to toll existing interstates as a means to generate transportation revenue takes an old, bad idea and makes it even worse. As members of Congress bristle at the thought, Foxx has recently tried to backpedal, saying that the tolling piece is a “smaller piece of our bill” and is not the primary method of generating revenue. However, no amount of obfuscation will change the clear language of the bill or hide the facts: it is an inefficient double tax on interstate drivers and it will divert billions of dollars of collected toll revenue away from interstate highways. The national transportation infrastructure revenue shortfall is a serious public policy issue that demands congressional attention. However, neither the Senate nor the House should approve tolling existing interstates in its highway reauthorization bill.

Miles Morin is a spokesman for the Alliance for Toll-Free Interstates.