The verdict on the "road diet" through downtown Petaluma is split.

It is winning some praise for providing roomier traffic lanes. Yet it also confusing many motorists who mistakenly assume that the diagonally striped center is off-limits when actually it can be used for loading or passing parallel parkers.

The project, on Petaluma Boulevard between Washington and D streets, was finished this summer and city engineers have been studying it to determine how well it's working.

The two crosswalks seem to be causing additional backups through the corridor when pedestrians activate the blinking lights. The crosswalk lights operate independently of the traffic signals, so while traffic may have the green light, pedestrians wanting to cross can stop the flow of vehicles at any time.

"I'm not convinced," said driver Karen MacLamore, whose car was sitting in a line of vehicles stopped for a loose group of pedestrians meandering across at Putnam Plaza. "There's more room, but I thought it was supposed to go faster after this."

The diet reduced Petaluma Boulevard through much of the downtown shopping district from four narrow lanes to two wider lanes with a cross-hatched center lane.

A similar change was completed north of Washington Street in 2008 and has been well-received.

Downtown, though, includes competing interests from pedestrians, bicyclists, motorists, merchants and shoppers wishing to park.

City traffic engineer Curt Bates said preliminary figures show the corridor is safer, with fewer side-swipe collisions. In a three-year period in 2009, when the funding grant was applied for, there were 90 collisions in the corridor. Since the work ended in mid-June, there have been 6.

After initial delays at the intersections, problems have eased as drivers get used to the new configuration, Bates said.

"The trend is encouraging," he said.

Merchants aren't so sure, said architect Ross Jones of the Petaluma Downtown Association. Anecdotal evidence shows sales are down since work began, he said. His group has asked the city if sales-tax information could be analyzed to determine if the perception is true.

Mayor David Glass said the project has improved safety, but acknowledged there may be some "tweaking that needs to be done." That may include timing the crosswalks to the traffic signal cycles or removing the on-demand feature.

City workers will look at better coordination of the signal lights and what may be the best way to handle problems that crop up when delivery trucks park in the middle lane to load and unload. That is allowed, but creates line-of-sight issues and backups when traffic has to stop for delivery workers to cross the lane.

(You can reach Staff Writer Lori A. Carter at 762-7297 or