Electronic tolling could enable Connecticut government or for-profit corporations to track driver speeds, locations and travel habits absent privacy protections, according to the state’s American Civil Liberties Union office.

Gov. Dannel Malloy issued an executive order on July 17 directing state agencies to conduct a $10 million comprehensive assessment of putting in place electronic tolling as a replacement for Connecticut gas tax revenues, which have declined as vehicles become more fuel efficient or entirely electric.

Malloy’s order makes no mention of privacy concerns, which the ACLU says is a major oversight.

“Thousands of detailed scans about your travel habits are kept in a state database, without rules for how the government secures or shares them,” said David McGuire, ACLU of Connecticut executive director, in a Wednesday blog. “If this toll study ignores privacy rights, this could be the reality in Connecticut.”

Typically electronic tolling relies on equipment that scan transponders attached to drivers’ windshields, deducting money from prepaid accounts linked to license plates. Cameras capture license plates of drivers not in the system, and the state mails them a bill.

Ensuring out-of-state drivers pay their fair share for the operation and maintenance of Connecticut highways was another reason Malloy cited for the study.

“After all, we need to be truthful with the people we were elected to represent—without transforming the way we fund our highways, we will be unable to pay for the large-scale construction and rehabilitation projects that our state needs to ensure continued safe travel while attracting businesses and growing our economy,” Malloy said in a statement.

Electronic tolls generally depend on automatic license plate readers, or LPRs, that may photograph a vehicle’s occupants. Connecticut government could then share those images with its partners, which the ACLU says raises Fourth Amendment concerns.

In the past, the Connecticut Capitol Area Police Association has partnered with LPR company Vigilant Solutions, which has a contract with U.S. Immigration and Customs Enforcement allowing the federal agency to access its full database of scans.

“This could allow ICE to find and follow immigrants by tracking cars registered to people who are undocumented or to their friends or family,” McGuire said. “If Connecticut does not restrict how it shares toll information, state tolls could become an on-ramp for the federal government’s deportation machine.”

A day after Malloy issued the order, ACLU of Connecticut sent a letter to Department of Transportation Commissioner James Redeker requesting a meeting to discuss privacy issues.

Neither Malloy’s office nor Redeker’s responded to requests for comment on their privacy stances.

There’s currently no deadline on the electronic tolling study, and there are no tolls on state roads.

ACLU of Connecticut is looking for the state to ban the sale or sharing of toll information with third parties, including federal agencies like ICE or the FBI. They also want rules that would require law enforcement to obtain a warrant to access the database—outside of emergencies like AMBER Alerts. People should be notified before their data is released in this way, McGuire said.

Connecticut has had the same 25-cents-per-gallon gas tax since 1997, though the state’s wholesale fuel tax rate was increased to 8.1 percent in 2013.

Electronic tolls will be considered on I-95, I-91, I-84, the Wilbur Cross Parkway, the Merritt Parkway, and other limited access highways identified by Redeker. The State Bond Commission cleared $10 million for the study Wednesday.