The I-95 Corridor Coalition, which represents transportation agencies, toll authorities, and related organizations, applied for a federal grant last month. The Washington Post reports that the funding would allow Delaware, Pennsylvania, Connecticut, and New Hampshire to test methods that could replace a gas tax, charging drivers a fee based on how many miles they’ve driven to fill “the gaping hole” in the country’s transportation funding.

“The idea is to get folks comfortable that mileage-based user fees are a feasible, reasonable and easy-to-use approach,” executive director of the I-95 coalition Patricia G. Hendren told the Post. The concept has been tried already in Oregon, and California will begin testing it next month.

However, a mileage tax has been very unpopular among the public. A recent survey by the Mineta Transportation Institute found that support ranged between 23% and 48%, depending on how the question was asked. It had more support when the hypothetical tax depended on the amount of pollution a driver’s car emits.

Various methods are being considered including a counting device plugged into the car, a device hooked up to gas pumps, cellphone apps, and GPS. Hendren said that any approach that’s implemented “will offer the option to simply pay an annual fee.”

Delaware’s secretary of transportation and chair of the coalition, Jennifer Cohan, explained that even though a mileage tax is unpopular, they essentially have no choice. “Reliance on the gas tax as a major contributor to funding transportation is no longer a viable option,” she told the Post. The federal gas tax hasn’t been raised in more than two decades and currently stands at 18.4 cents per gallon, and efforts to increase it have been unsuccessful.

“Whatever it ends up being, at least we’ll have data,” Cohan said about testing the mileage tax. “We’ll actually have something to show: This is what it will look like if we actually implement it.”