Tuesday is the deadline to comment on a Virginia Department of Transportation proposal to charge $1 per month for each E-ZPass transponder.

The proposed monthly fee will help VDOT administer the E-ZPass program, whose numbers are expected to double over the next several years, said VDOT spokesman Tamara Rollison.

The measure, which might be implemented this summer, comes as a number of new toll facilities are about to open elsewhere in the state, several of them relying on all electronic toll collection, Rollison said.

The proposed monthly fee would cover costs for buying nearly one-half million transponders, Rollison said, as well as implementing a retail program where transponders can be obtained at various stores in Northern Virginia and eventually in Hampton Roads. Also, the extra fee would help pay to provide service at select Department of Motor Vehicles locations, she said, as well as upgrading information technology to accommodate the expandable program.

The fee addit...