ROSLINDALE (CBS) -- It's been a long time since anyone's seen gas below $2 a gallon in Massachusetts.

But at Costco in Dedham and US Petro in Roslindale, a gallon of unleaded has dipped to $1.99, and drivers are thrilled.

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"Everyone's happy, they're loving it," said Justin, a worker at US Petro in Roslindale.

Business appears to have doubled since prices fell under $2, Justin told WBZ NewsRadio 1030.

"I haven't seen gas this cheap in forever, it's been a long time," he said.

The average cost of a gallon of gas has dropped for 17 straight weeks and is $2.36 in Massachusetts, according to AAA.

"Lower gas prices continue to be welcome news for consumers, who are saving an estimated $500 million each day," said AAA spokeswoman Mary Maguire in a statement. "Barring any unforeseen circumstances, AAA sees no reason for this trend not to continue in the short term."