Rate Making

I'm wondering about railroad rate making during the
regulated era (pre-1980). How much, if any, leeway
did railroads have in setting rates during, say, the
1940s-50s? Could a railroad, or combination of roads,
underprice their competition if they were otherwise
hapered by a longer or slower route? Where multiple
competitors offered service between two terminals,
did the shortest route have lower rates? The one
with the lowest grades? Or were the rates regulated
to be the same so that railroads had to compete on
service?

- Ed Kyle