It is now easier to get across Petaluma and safer to get on the freeway from East Washington Street, transportation officials declared Monday as they inaugurated a newly improved interchange through the heart of the city.

The $23 million East Washington Street interchange was completed 10 months early, even after the original source of funding for Petaluma's portion was wiped out by the state.

It is the first completed project on the Sonoma County side of the Sonoma-Marin Narrows project, which will eventually widen Highway 101 and improve access points from northern Petaluma to Highway 37 in Novato.

"This is another successful project delivered," said Bijan Sartipi, district director of Caltrans. "This project is ahead of schedule and within the budget. That is very important these days."

The project was due to open next August, but crews were able to move utility lines sooner than expected, said Caltrans spokesman Allyn Amsk. The improved interchange includes a realigned and wider northbound off-ramp and southbound on-ramp. The centerpiece of the project, a new northbound on-ramp for vehicles traveling west on East Washington, opened in September.

The project was funded partially through Sonoma County Measure M sales tax dollars, and the federal and state money that it leveraged. Petaluma had committed $4 million in redevelopment money, but the city lost access to those funds after the state did away with redevelopment agencies in 2011.

The city, claiming that the funds were already dedicated to an ongoing project, sued the state and lost. Instead, Petaluma is paying its portion of the project from development impact fees, Mayor David Glass said. Those fees are paid by developers of large, traffic-generating projects, such as the Target shopping center and the Friedman's Home Improvement store set to open next year.

"Development impact fees are the funds that backfill and pay for this project," Glass said.

Improved cross-town access long has been an issue in Petaluma, a city divided by Highway 101 with just five places to cross. In 1993, Janice Cader-Thompson and other Petalumans started lobbying for improvements on the East Washington Street overpass, the main east-west crossing and a frequent bottleneck.

Twenty years later, Cader-Thompson, who became a city councilmember and helped secure much of the funding for the project, was happy to see the payoff of her work.

"It started off with a vision," she said. "It's a great feeling of accomplishment to see the project work."

David Rabbitt, a Sonoma County supervisor and a director of the Sonoma County Transportation Authority, said the project is one piece in the larger Narrows project. Construction crews are improving four other interchanges, widening the Petaluma River bridge and building frontage roads between northern Petaluma and Novato in preparation for carpool lanes, which could be in place by 2020.

"It is an integral part of the puzzle as we continue down the corridor," said Rabbitt, whose district includes Petaluma. "We still have a ways to go, but it's nice to see something complete."

Amsk said drivers still will see cones and construction crews on the East Washington Street interchange for about the next two weeks as they finish the last details, which include smoothing the street and installing signs.

Petaluma drivers already have noticed an improvement in traffic flow on the overpass. Alison Abbott, a spa director who lives on the eastside and drives over the freeway daily, said she likes the upgrades.

"I'm happy with what they did," she said. "It flows nicely."

Some drivers said the interchange could be improved even more. Eastbound drivers on East Washington Street headed north on Highway 101 still use the circular on-ramp with its short merging lane. And the project did not touch the southbound off-ramp with a tight turn that requires drivers to decelerate quickly.

Others focused on the need for an additional cross-town connector. The city long has had plans to extend Rainier Avenue across the freeway, but doesn't have the funding.

"Another overpass is definitely needed to alleviate traffic," said Gary Brodie, owner of Brodie's Tire and Brake.