It prolly depends on the area. When I was in Burbank, CA, I saw an incredible amount of the elderly. I didn't realize it was such a retirement area since so much media is there. But, aside from the idiot drivers that come in all stripes (basically, the too aggressive), the elderly did have a proportionately high part of the near accidents I witnessed. Personally, I saw at least 4 incidents of a person driving on the wrong side of the street. All were the elderly.
In other areas, where the elderly weren't as pervasive, I'm sure drunks caused most of the real bad problems.