By the 1960's, muscle cars and larger semi tractor trailers were the norm and the lanes had about two inches of "extra" room per lane.
The wind was always blowing, so you almost had to treat your car like an airplane and set the trim for the prevailing winds, then a larger truck would come by and disrupt the airflow and cause your car to either "shift" into the oncoming traffic or hit the outer ledge of concrete, all of three inches high and two inches wide, just under the guardrails. The guardrails were also 1/4 inch thick angle iron.
It was like riding a roller coaster in a high wind while standing on the seat. As small children, my brother and I would close our eyes when Dad drove over it on numerous family trips to Charleston.
It didn't help matters any when a columnist for the Charleston News and Courier, nom de plume of Ashley Cooper, noted in his column that a new bridge was going to be necessary as the old one was drifting down river about an inch or two a year.