The sun is setting on the iconic police cruiser, Ford's Crown Victoria, and its first slick replacement has hit Sonoma County streets.

A sheriff's deputy is now cruising the north county beat behind the wheel of a prototype Police Interceptor, Ford's 2013 model based on the four-door Taurus with a battery of improvements from engine to aesthetics.

"It's like going from a rotary phone to a smartphone," said David Worthington, the county's assistant fleet manager.

The county bought 14 Interceptor sedans and four SUV models during the last fiscal year and will gradually blend them into the fleet over the next 10 months. It expects to completely convert the patrol fleet to the Interceptor within about four years.

The last "Crown Vic" rolled off the line in 2011 after more than two decades of being the nation's preferred cop car. With a V6 engine and rear-wheel drive, the Crown Vic was known for durability. But beneath the classic silhouette, the Crown Vic was sorely in need of an update, Worthington said.

Gone are the days of careening around corners on two wheels as in the movies, fleet manager Dave Head said. The Interceptors are all-wheel drive, a boon on the county's more rugged areas, and have an on-board computer system that adjusts suspension among other things to provide greater stability, Head said.

Perhaps the greatest concern among the rank and file is whether the tallest and broadest deputies -- and about 15 pounds of protective gear and weapons they wear -- will fit into the new cars.

The Interceptor certainly appears more sleek than the boat-like Crown Vic, with a black, instead of beige, interior.

Jeff Cortner, who supervises the county's auto technicians, said they took out measuring tape and compared the two models.

The Interceptor came out ahead in all but three categories. The new cars have about 2.25 inches less headroom, a half-inch less room for shoulders and the doors open with an inch less width.

But the driver's seat in the new car is 2.5 inches higher off the ground than the Crown Vic's, which could make it easier to get in and out of the cruisers. The foot well is 1.25 inches longer and a passenger behind the driver has nearly 2 more inches of legroom.

The windows are smaller, particularly in the back.

The county's auto techs spent about five months of tinkering and tuning. On Wednesday, Cortner opened the back passenger door of a second Interceptor his team is working to get road ready.

The car didn't have back seats because county technicians were installing two sturdy steel support bars that are designed to bolster the car so it can withstand being rear-ended at 75 mph, Cortner said.

The county worked with a Sparks, Nev., company to design custom plastic bucket seats for the back, where prisoners sit, to give the driver more room.

Deputy John Blenker patrols about 400 square miles in the county's north, including rough, winding roads like Stewarts Point-Skaggs Springs, Rock Pile and Ida Clayton.

Blenker started his career with Sonoma County in the boxy Crown Vic, a precursor to the curvy body introduced in the early '90s.

Four unused Crown Victorias remain in the county's fleet ready to be cycled in as patrol cruisers retire.

The average patrol car travels about 30,000 miles each year and is retired after 90,000 miles, Head said.

Blenker, who is 6-foot-1, said the space in the new car is fine and the visibility could be better. But the major benefit is the way the car handles Sonoma County's rutty, windy, rural roads.

"It handles the roads amazingly -- and I'm not getting a kickback from Ford," Blenker said. "I just like a good car. This is our office. We have to be in it 11 hours a day."You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.