You guys are mistaken and need a reality check if you think that you can actually refuse a search. If a cop thinks there is weed, he is going to search the car, and most of the time it actually will smell from where he is if its inside the car and not in the trunk.

First off, if you refuse to a search you immediately raise suspicion level. Second, they can always claim to have smelled the weed initially which would justify searching you.. and since he would have then found the weed, it would hold up.. But most of the times when a cop makes a traffic stop (something he does dozens upon dozens of each day) its not going to be on his mind unless you do something to make it obvious.

Oh btw, third: K9 units can search the car because the dogs can even smell it without even getting into the car (thus, not searching your stuff) and at least around here a K9 unit could be on the scene within 5-10 minutes.