The gear track on MD-88 is 16'8", so half spread is 8'4". Add in the 30' allowable deviation at Vmcg for 38'8" from runway centerline to outside centerline (not outside wheel tread!) as where the mains would be in the OEI event near Vmcg. Double that and you have absolute minimum runway width of 77'4". That doesn't account for the outboard tire or any allowance for crosswind or pilot "deviations". 30m or 98' is a sensible min width.
EDIT:
Check certification standard, it might have 25' or 30' as the allowed deviation changed. I'd guess the MD-95 B717 was at a later 25 amendment