The average lane width is 10'. Of course this varies but that is the average of a rural 2 lane road. Highways are 12' widths. Therefor for a undivided 2 lane road I would think 5' either side of the center would be more accurate than 4'. On 4 lane divided highways I would guess 20' average difference from center. Therefor a 100' diameter curve on a 4 lane divided highway would be 80' diameter going right versus 120' going left. Still a tight curve and only about 17% difference in distance. But what is the road angle at the center of the lane due to the average crown? I can't seem to find the data but is is more then 1 or 2 degrees off at the lane center versus road center? Does that adequately explain the left side wear at 5 to 10 degrees off center? IDK. But I suspect both theories come into play.
response #12 with my calcs was on the prior page
ex:
90 degree turn, dt= distance travelled
25 ft center rad, right turn 21 ft r. (33' dt), left turn 29 ft r. (45.6'dt) =28% diff.
60ft center rad., right turn 56' r. (88'dt), left turn 64' r. (100.5'dt) = 14% diff
100 ft center rad., right turn 96' r. ( 150.8'dt), left turn 104' r. (163.4'dt) = 8% diff.....