Roman drivers finally got some relief on Monday when, after 450 days of traffic chaos and unprintable curses, a ribbon-cutting ceremony heralded the opening of an underpass along the Tiber River near the Vatican that immediately cleared traffic from what is now Rome’s largest pedestrian area.

The new underpass is part of the makeover Rome is undergoing as it readies for the 32 million visitors the Vatican expects in 2025 for the Roman Catholic Church Jubilee — a year of faith, penance and forgiveness of sins that takes place every quarter century.

Romans have conflicting feelings about it.

“It’s a miracle” that so many public works have been completed, said Rome’s mayor, Roberto Gualtieri.

“It’s been an ordeal,” said Martina Battista, 23, a medical student in Rome who was evicted from her apartment because her landlord wanted to turn it into a bed-and-breakfast for the Jubilee.

Mr. Gualtieri said that the Jubilee was a great opportunity to refurbish Rome and turn it into a greener, more inclusive city, with hundreds of projects planned. But if Mr. Gualtieri and Vatican officials have spent the better part of December at a flurry of inaugurations of spruced up monuments, repaved streets and new pedestrian piazzas — the upside of the holy year — the surge in pilgrims is expected to take a toll.

Construction sites for Jubilee works have left key parts of Rome bruised by detours, leading to interminable traffic jams and very grumpy citizens.