I can't speak for you straights...I haven't a real clue..as far as CV's tho....the flat rate system sucks for drivers..it is a money pit for carriers....
PS there should be NO formula....you should get 100% of what is billed...
Not sure what your former carrier did. I know I'm not makin' a killing off of CV freight, whether you want to call it the tariff OR the FSC. Why do SOME carriers (I can't speak for all) use a "flat rate" or a "sliding scale" type surcharge? Because there are times when my company is not even making as much "FSC" money on a load as I am paying out to keep up with the price of fuel. Since the beginning of December I have watched CV rates go into the toilet for everyone, even while the fuel prices are still rising.
Here's what I do: My guys get a base rate plus a steady surcharge, OR they get a certain percentage of the load, depending which is greater. But because I have a small company and can make the call, there are times I try and give a driver much better. For example, last fall, a certain large 3PL sent an email about a 618 mile van load to be picked within 2 hours. My closest van was 170 miles away. Well, that email was resent several times, so I contacted them and made an offer. I called my guy and this is what I offered him: Instead of loaded miles plus fuel, plus $30 or so DH money, I offered him an extra 150 loaded mile pay, including that "flat rate" surcharge.
So in the end, my driver received base rate, plus fsc for 768 miles, instead of 618.
For us, the flat rate works well, as a driver always know what he is getting as a minimum, without needing 15 minutes to mull over to see if he wants it or not. Plus, we normally don't mess with those little 150 milers going between auto plants in the midwest.