At Viva Cocolat in Petaluma, customers can enjoy a gourmet truffle, a luscious chocolate bar and, at the right time of day, the view of a traffic jam through the picture windows.

The popular chocolate shop in downtown Petaluma sits along a bustling strip of Petaluma Boulevard where city leaders are planning a "road diet," which has nothing to do with the indulgent treats chocolatier Lynn Wong prepares inside.

The idea is to reduce Petaluma Boulevard from four narrow lanes to two wider lanes with a two-direction turn lane in the middle from East Washington Street through the heart of the downtown shopping district. A similar change was completed farther north on the street in 2008.

Traffic engineers say the reconfiguration will make the road safer for all travelers — motorists, bicyclists and pedestrians — who all have to share the tight space. Collisions, especially side-swipes, are expected to be reduced by more than a third with the new configuration.

But some downtown merchants have concerns that the reduction in lanes and the elimination of some parking spots could make shoppers avoid the area.

"I see traffic every day through my windows," Wong said. "At key times, it's completely backed up. And that's with two lanes. I can't even imagine when it's just one lane what it's going to be like during those congested times."

City traffic studies of Petaluma Boulevard North show a decrease in collisions, from 20 to 9, after the 2008 road diet, while traffic volume remained the same.

Senior engineer Erica Ahmann Smithies said the project will add to the total number of parking spaces downtown. While a few will be lost on the north end, 18 will be added closer to the Theatre District, between C and E Streets.

Downtown Association president Jeff Mayne said most merchants are happy with the city's adoption of their suggestion to reopen Water Street to parking as part of the diet. About six years ago, the city removed some parking along the Petaluma River behind businesses as part of a rehab of Water Street.

"That's everyone's deal: where are people going to park when they come in to my restaurant, my store, whatever," he said. "That, to us, was a really big win to have the city listen and respond."

The City Council has approved the project, which will come before them again this summer to awarding a construction contract and add the Water Street parking idea, Ahmann Smithies said.

Work could start in late July or early August.

If the city approves the Water Street parking, that would ease the parking crunch, Wong said.

"Out of towners find it very frustrating to find parking," she said. "They never say the streets are too narrow."

Also to ease merchants' concerns, Ahmann Smithies said, work must be done before the holiday shopping season begins, must stop on the weekends and lane closures will be minimized.

Eighty percent of the $610,000 project is funded through a regional traffic grant, with the city using about $122,000 it has from state transportation bonds funds.

Contact Staff Writer Lori A. Carter at 762-7297 or