Sonic, America's Drive-In, (a hamburger and shake joint with drive-through, and car-hop service,) earned city approval Thursday for a restaurant in the parking lot of Expect Discount and Nardelli's Restaurant on Newtown Road.

Work on the restaurant is expected to start in the spring.

The restaurant in the parking lot will force drivers to change how and where they drive in the lot. A Sonic restaurant is so popular and it attracts so many cars, the city's review largely focused on how cars will come and go from the lot and where they will line up for the restaurant's drive-through and car-hop service. The plan forced the city's planning officials to review the traffic pattern in the lot and in the neighborhood. The state Traffic Commission reviewed the plan and approved it, as did the city.

Sonic's first Connecticut restaurant opened in Wallingford on July 14, 2010, causing Connecticut Gov. M. Jodi Rell to declare it "Sonic Day" in Connecticut. Cars started lining up for the restaurant four hours before it opened. Interested people visited the site under construction to see when it might be opening.

The restaurant offers people three places of where to eat. People can use the drive-through, like many other fast food restaurants. They can sit outside on the patio and eat, or they can park in a parking place called a stall, and order their food and sit and eat in the car.

Sean Hearty, the permit center coordinator, said the traffic issue in the Expect Discount parking lot was complicated. He said the city had already approved a restaurant on this same spot in 2007 (at that time it was a Starbuck's with 24-hour drive-through service,) but that was never built. Sonic avoided commission review because of the previous approval. The planning staff reviewed this proposal and approved it Thursday.

Sonic is based in Oklahoma City, and it has 3,500 drive-ins in 42 stats coast to coast. More than 3 million people eat in Sonic restaurants every day. It has locations in New York and Massachusetts.

In Connecticut, Wallingford is open and Manchester is approved. Other tentative locations include Milford, Berlin, New Haven, Southington, Enfield and Hartford.

The Danbury location will open in 2011.