The average price of on-highway diesel fuel fell below $2 for the first time since Feb. 14, 2005. Diesel prices came close to that mark in 2009 but never fell below it.

The price of a gallon of diesel fuel fell by 2.8 cents last week, settling at $1.98. The price is 88.5 cents cheaper than the same week a year ago.

Falling diesel prices reflect both decreasing crude oil prices and increasing inventories of crude oil and refined products worldwide, according to the Department of Energy.

Prices fell in regions across the country, with the Rocky Mountain region seeing the largest drop at 5.3 cents. The smallest change was in the Lower Atlantic region, where prices fell 1.2 cents for the week.

The average price of a gallon of regular gasoline is also below $2 per gallon, a mark it passed just over a month ago. Last week prices fell by 3.5 cents to $1.724 per gallon nationally. The price is 55 cents cheaper than it was in the same week of 2015.

Regional gasoline prices fluctuated significantly last week with prices falling by as much as 9.5 cents on the West Coast while the Midwest actually saw a slight increase of 0.4 cents per gallon.

On Wednesday, there was an important indicator that crude oil prices may rebound. Iran indicated that it may freeze its production levels rather than increase output as it had originally planned, according to a Market Watch report.

After being released from economic sanctions as part of the U.S. and Iranian nuclear agreement, Iran initially indicated that it would increase crude oil output despite already high global production levels compared with demand. But after meeting with other oil producing countries, Iran’s oil minister expressed the country’s support for a production freeze to boost oil prices. As a result, early market trading on Wednesday indicated as much as a 7% boost to oil prices.

Related: Diesel Prices Are Down Over 82 Cents in 12 Months