The state is owed nearly $700,000 from unpaid Tobin Bridge tolls — with the five worst abusers racking up $1,500 in charges — in the two months since the toll booths were torn down and a cashless electronic tolling pilot program was put in place, a Herald analysis shows.

The $696,424 in uncollected tolls accounts for nearly 15 percent of the $4.8 million in overall toll revenue the state should have received since the state Department of Transportation implemented the cashless “open-road tolling” system July 21 on the inbound side of the Chelsea-Boston span, according to MassDOT.

The agency, whose officials have stated they want to expand electronic tolling to other highways, was unable to provide a breakdown of where the drivers who owed Tobin toll money were from, but acknowledged the cashless system could be abused by motorists from other states who refuse to pay their debts because Massachusetts has no way to collect or penalize the deadbeats.

MassDOT said it is working to expand its first-in-the-nation “reciprocity agreement” that it struck with New Hampshire and Maine in 2011. That pact allows it to go after Granite and Pine Tree state scofflaws, like it does with Bay State toll evaders, by forcing them to pay their delinquent debts before they can renew their licenses and vehicle registration, said MassDOT spokesman Michael Verseckes.

Gregory W. Sullivan, the former state inspector general who has studied the toll wars between Massachusetts and New Hampshire, lauded MassDOT for knocking down the Tobin’s toll plazas but said the agency should have struck accords first with other states, particularly ones that border the Bay State.

“(The) decision to go toll-less was a good thing because we are ending the era of the $75,000-a-year toll collector, which was an abuse to the taxpayers, and people won’t have to wait in long lines at the toll plaza to pay a toll,” said Sullivan, the research director at the Pioneer Institute, a conservative think tank. “But we have to toughen up our position to get cooperation from all the regional states, and we haven’t done that. Massachusetts should have demanded reciprocity agreements from Rhode Island, Connecticut and New York before we took the tolls down.”

Verseckes said since the Tobin’s toll stations were removed, 42,591 new E-ZPass accounts have been opened, and now more than 80 percent of motorists crossing the inbound bridge have transponders, compared to 67 percent on average in 2013.

Verseckes added that while ?E-ZPass holders are automatically deducted a $2.50 toll for each inbound crossing, vehicles without a transponder have their license plates photographed and then are sent monthly bills charging them $3 — the old cash toll — for each crossing.

The five worst abusers, alone, owe a combined $1,498 in unpaid Tobin tolls, according to MassDOT.

Massachusetts motorists, who make up 80 percent of the Tobin drivers, face up to $90 dollars in fines if they don’t pay their toll bills within three months.

“We are only 65 days in the all-electronic/cashless tolling system — meaning we are not even at the point where anyone’s registration or license would be marked for nonrenewal for nonpayment of electronic tolls on the Tobin,” Verseckes said, adding “because this system is so new, we have started to reach out to customers who have accumulated large toll balances to explain how the Pay By Plate system works.”