By year's end, car shoppers could be making their purchases from the comfort of their own homes.

General Motors plans to offer a new online shopping program to all 4,300 of its Chevrolet, Buick, GMC and Cadillac dealers, CBS News reports. Potential buyers can check inventory through a dealer's website and negotiate the price. When they decide on a car, they can have the new vehicle delivered without ever walking into a showroom.

Buying cars online could become the norm if GM's new plan catches on.

"If GM can make this work, it will have a ripple effect on other automakers," Karl Brauer, senior analyst for Kelley Blue Book, told CBS.

GM has piloted the online car sales initiative with 100 dealers in eight states, calling the program "Shop-Click-Drive." Shoppers can go online to select participating dealers. They can also arrange financing and get an estimate on the value of a trade-in, according to GM.

All transactions must be routed through GM's dealers because of state franchise laws that protect those dealerships, according to CBS. Electric car company Tesla is attempting to sell directly online with the argument that the laws do not apply to its transactions because it never had any franchised dealers.

Whether or not buyers end up purchasing cars online, the site can be useful for research.

"Shoppers are better served when they research transaction prices, confirm what the relative pricing range is for a car, then work with multiple dealers until they find one willing to sell them the vehicle in the lower end of that range," Brauer said.

Experts say online buyers should follow the same rules they would if they were at the dealership. Shoppers can get the best deal if they know the target price of the car they want, get financing approved from a bank or credit union in advance and resist most add-ons.

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