motion blur lights

[laxman15]

hey everybody i'm trying to find out how to blur the taillights on a car to make it look something like this: http://photoshoptutorials.ws/images/...6060_size1.jpg and yes I know that is done be slowing the shutter speed on a camera but I wan't to know if it is possible to do in photoshop. I want it to look like http://bp0.blogger.com/_JtbuvNJSmFc/...8+_DSC3139.jpg

any help appreciated :