Clarification: An earlier version of this article stated that nearly 650,000 vehicle owners had racked up $6.7 million in unpaid tolls dating back five years. The article also said about 15,000 individual owners owed more than $500 each. The article should have made clear that the money owed by individual vehicle owners included both unpaid tolls and penalty fees. This version has been updated to clarify that fact.

Motorists who drive through E-ZPass lanes at Maryland toll plazas without an E-ZPass transponder soon could have their vehicle registrations flagged for nonrenewal and possibly suspended if they don’t pay the tolls by mail.

Legislation that passed the Maryland General Assembly on Friday allows the state to issue $50 civil citations for toll bills unpaid after 30 days. Refusal to pay the citation or contest it in District Court would result in the vehicle’s registration being flagged for nonrenewal until the debt is paid. After multiple violations, the registration would be suspended, which would allow police to impound the vehicle, state tolling officials said.

“You can ignore citations and you can ignore notices of toll due, but at some point you have to deal with your vehicle registration,” said Harold Bartlett, executive secretary for the Maryland Transportation Authority. “This gives us more teeth.”

The new law also would allow the Maryland tolling authority to enter into reciprocity agreements with other states. That would allow Maryland to pursue out-of-state toll violators, who are responsible for about one-fourth of the state’s toll debt.

Legislators undertook a review of the tolling issue this year after The Washington Post highlighted how the existing law was hampering efforts to collect outstanding debts.

The Post found that, as of late last year, nearly 650,000 vehicle owners had racked up $6.7 million in unpaid tolls dating back five years in Maryland. One car rental company owed nearly $209,000, while about 15,000 individual owners owed more than $500 each in both unpaid tolls and penalty fees.

The Post also found that nearly one in three motorists who use the Intercounty Connector without an E-ZPass transponder never paid the toll by mail.

The impact of toll scofflaws has begun to draw more attention nationwide as states rely increasingly on anticipated toll revenues to finance major construction projects, including the $2.56 billion ICC in Maryland and the $5.6 billion Silver Line extension of Metrorail under construction in Northern Virginia.

Current Maryland law allows for vehicle registrations to be suspended for nonpayment of tolls, but the Maryland Motor Vehicle Administration hasn’t pursued that in almost three years because the tolling authority doesn’t enforce the law as written.

The law required that a citation be issued to anyone who passed through a toll booth without paying. However, Bartlett said that didn’t allow for relatively recent “video tolling,” which permits motorists without an E-ZPass transponder to pay a higher toll rate by mail. Under the new law, a citation is incurred only if the vehicle owner ignores the mailed notice of toll due for 30 days.

A vehicle’s registration will be flagged for nonrenewal after one $50 citation goes unpaid, Bartlett said. After an owner incurs $1,000 in unpaid tolls and fines, the vehicle’s registration will be suspended, he said.

Bartlett said tougher enforcement became necessary as the state began to move to all-electronic tolling on roads such as the ICC, where there are no toll booths. Motorists on the ICC must have an E-ZPass transponder or pay later by mail.

The governor is expected to sign the legislation, which would take effect July 1.