If you're looking to implement a mileage number, 900 miles seems to be about the sweet spot. When dispatched at 45 MPH it's 20 hours, and at 50 MPH it's 18 hours. But a van can average a good 62 MPH over that run, including fuel stops, and can drive it in about 14½ hours. That leaves a couple of hours in there for a nap along the way if one is needed.
Between 900 and 1400 miles it gets iffy, because in most cases (other than those rare occasions where the driver just woke up after a full night's sleep and is well rested before getting the load) you can't drive more than about 14 or 15 hours without significant, meaningful sleep in order to continue driving. At 1200 miles, for example, dispatched at 50 MPH it's 24 hours to get it there, and at 62 MPH it's 19¾ hours behind the wheel, call it 20, plus losing another hour for fuel stops at 21 hours. That only leaves a maximum of 3 hours for a nap along the way, which won't cut it in most cases. Extra time, about 5 hours or so, will need to be built into the run.
But, once you get up around 1500 miles, it gets easier to drive it. At 50 MPH that's 30 hours, and at 62 MPH it's 24 behind the wheel, plus an hour for fueling, and you have a good 5 hours to spare for a nap and something to eat.
And of course, if it's booked even at 47 MPH instead of 50 MPH, those 3 MPH can make all the difference in the world in a 1500 mile run. It turns a 30 hour dispatch time into 32 hour run, giving the driver 7 hours to ensure they are well rested and alert for the entire trip. Even a 900 mile run benefits from those 3 MPH, giving the driver an extra full hour to lessen the stress.
So, if looking at implementing straight-through travel times, I believe that straight-through dispatch times should be looked at, as well. Less than 900 miles and a dispatch time of 50 MPH seems to work well. But, at longer distances, 47 or 45 MPH should be the norm, since those extra couple or three hours can make the difference in safe versus marginal, help provide for unexpected delays like construction or traffic, and those couple of hours aren't likely to make any difference to a shipper or a receiver in the first place, otherwise they've have air expedited it.
Longer loads especially, booked at 47 or 45 miles an hour, your CSA scores will thank you. Fewer speeding tickets.
