The effort to modernize a Boston toll plaza may be a temporary annoyance to drivers, but it’s only made worse the delays at another site, occasionally brought on by a recurring disaster.

Drivers heading southbound into the Tobin Bridge toll plazas on Highway One are facing a temporary change in a lane configuration, as the two left toll booth lanes are now blocked. The booth closings are part of ongoing work on the bridge, as the Massachusetts Department of Transportation prepares to remove the entire toll plaza later this year.

“By blocking these two lanes, we’re really going to get a good look at what needs to happen, what sort of equipment is in the pavement, maybe electrical systems that we’ll need to remove, once we are all electronic and the toll booths come down,” MassDOT spokeswoman Sara Lavoie told WBZ NewsRadio 1030. Lavoie was referring to the conversion of the Tobin toll booths this summer, to completely electronic transactions. They will no longer be accepting cash.

Already experiencing these delays in daily southbound commuter traffic on 1A, drivers seeking alternate routes are occasionally held back even longer by recurring accidents at an East Boston 1A overpass, known by locals as “the can opener.”

Around six AM on May 21, an eighteen wheeler loaded with home furnishings became lodged under the overpass, a day after police say a truck loaded with watermelons met the same fate. Traffic on Route 1A South toward Logan Airport was delayed about two hours.

Driver Michael Hunter was headed toward Somerville from Windsor, Connecticut, when two GPS systems directed him to make a sharp U-turn under the bridge. With heavy traffic behind him, his only alternative would have been to make a wider turn over a cement partition.

“I felt it get stuck but as I backed up, it got worse,” Hunter said. The overpass peeled the top open from front to back, as the truck became caught under the bridge. No injuries are reported in local coverage.

Rich Dembro, an employee at a nearby car wash, says he’s seen dozens of semis caught under the bridge, but never two days in a row.

Tow driver Scott Sainsbury, of Todisco Towing in East Boston, was called to the scene both days.

“The issue is they can’t read the sign,” Sainsbury said. He says the sign warning of the twelve-foot height limit is under the overpass. “I’m a truck driver, I keep my eyes peeled. If you’re not from this area, the GPS is telling you to go here … And you can’t see the sign.”

Although morning traffic was diverted around the site in a couple of hours, Sainsbury estimated that it would “easily be four or five hours” before the truck was removed.

Lavoie released an e-mailed statement in response to the May 21 accident, saying “MassDOT, BPD, BTD have a team on scene at this location right now to determine what happened and to prevent it from reoccurring… We are looking at improving signage, we are looking at possible physical roadway changes, perhaps extending a traffic island, to make the prohibited movement more obvious, as well as adding chains (to hang from the overpass) to serve as another clue to truckers that height is an issue in this spot.”