A major Petaluma road project, already behind schedule, will now be broken into two phases so downtown merchants can make the most of holiday sales.

The city is overhauling Petaluma Boulevard from East Washington Street through the heart of the downtown shopping district, similar to the change that was completed farther north on the street in 2008.

The so-called "road diet" will reduce the number of lanes on the street, but widen them and add a two-way turn lane in the middle. The change is meant to modernize the lane widths and create a safer environment for pedestrians, bicyclists and drivers.

But many merchants in the vocal and politically influential downtown association began to worry that work hadn't begun by its mid-September target.

Marie McCusker, director of the Petaluma Downtown Association, asked the city to delay the work if it couldn't be completed by Thanksgiving.

"This year, we saw the closure of more stores than I had seen in the five years previous downtown," she said. "They're vulnerable. And we're coming up to the most crucial time of the year."

Public Works Director Dan St. John said the city will live up to the commitment it made to merchants when the project was approved — that construction will not occur during the holidays, defined as between Thanksgiving and Christmas.

City Manager John Brown said the city is renegotiating with Ghilotti Brothers Contractors to stop work by Nov. 2, then clean up the work area for the holidays.

Work will be restarted in May, after the Butter and Egg Days Parade and the wet weather has passed.

Downtown business owner Richard De Carli said the city should have planned the work for the summer, maybe during the Sonoma County Fair when traffic is lighter downtown.

His Christmas Fantasia seasonal store in the LanMart building would be among the most at-risk of the dozens of shops along Petaluma Boulevard if construction was delayed too long.

"The downtown businesses need the winter to do their sales," he said. "All of our business, for our business especially, starts right now and goes until Christmas, then it's slack. So if we don't make our money through the Christmas season, we have no money to carry us through the year."

He asked the city to put off the work to "give the wound time to heal."

Jan Mettner, owner of Vicki's Secret women's consignment store near Western Avenue, said the whole road diet idea "is so ridiculous I can't get over it," a sentiment shared by many downtown merchants who worry it will discourage vehicle traffic from heading downtown.

She said her busiest season is the fall — when people are buying clothes for themselves before they're in gift-buying mode.

"I had a horrible season January through June, but now that is coming back," she said. "If they did the project in July or January, nobody's busy. Not the restaurants, not retail."

St. John acknowledges that not all merchants are satisfied with the construction project or its timing. But he said he has no doubts Ghilotti will finish the work as promised.

"They can move heaven and earth if they want to," he said. "We're not concerned that they're not going to meet the conditions of the contract. We're doing everything we can to meet the concerns we've heard from businesses."