Where the number comes from
Take the truck's last position and the receiver's coordinates, draw a line between them, divide by an assumed speed, add it to the clock. That is the ETA on most boards, and it has three problems stacked on top of each other. The line is shorter than any road. The speed is a guess that ignores what a truck can do. And the clock keeps running from a position that may be an hour old.
On a short lane the errors are small enough to hide. On a 600-mile lane they compound. The straight line from Dallas to Atlanta is about 720 miles; the road is about 780. Highway speed for a loaded truck in traffic is not 65. And the driver cannot drive 780 miles without stopping, which the calculation does not know. The result is an ETA that is optimistic by hours, delivered with a precision that makes it look measured.
A route for a truck, not a car
The first fix is to plan the distance on the road network, and to plan it for a truck. A 53-foot trailer with a 13-foot-6 box does not take the road a sedan takes: low bridges, posted weight limits, hazmat restrictions in tunnels, and truck-prohibited parkways all push it onto a longer path. Routing for a car and then adding a fudge factor gets the distance roughly right and the time wrong, because the detour is usually the slow part.
The truck the route is planned for can be worked out from the load rather than typed in by anyone. The equipment type says what the trailer is, the cargo weight plus a typical empty rig says what it weighs, and the hazmat flag says whether it can use the tunnel. That is enough to route for the standard interstate tractor-trailer, and it changes nothing for the dispatcher, who already entered all three when the load was booked.
What it still is not is the route the driver will take. The driver follows signs, their own navigation and the carrier's rules, and the plan does not know about the road closed at mile 212. So every route is a planning estimate and should be labelled one on the board and on the customer's page, in those words. A route that presents itself as the truth is the one that gets argued about.
The driver's clock
The second fix is the one most tools skip. A driver can drive eleven hours in a fourteen-hour window, must take a thirty-minute break after eight hours of driving, and needs ten hours off before the clock resets. A truck 420 miles out at 4 p.m. with three hours of drive time left is not arriving tonight, however fast it goes. An ETA that says 11 p.m. is not slightly off; it is a different day.
An honest ETA adds the driver's remaining hours to the calculation: drive time left today, the break if it falls inside the run, and the ten-hour reset if the run does not fit. Where the ELD reports the driver's clock, the board should use it. Where it does not, the board should assume a full clock and say that it assumed, so a dispatcher looking at a 3 a.m. arrival knows to ask the driver rather than to promise it.
How old the position is
The third input is the age of the position the ETA is built from. A truck that reported five minutes ago at highway speed is where the calculation thinks it is. A truck that reported ninety minutes ago is somewhere along a sixty-mile stretch, or parked, or at a fuel island with the engine off, and an ETA computed from that position is a number that has not been true for an hour and a half.
So the ETA carries the age of its position with it, and the board says plainly when that age is past the threshold you have set for stale tracking. Confidence is not decoration here. An ETA from a fresh position with a routed distance and a known clock deserves to be planned around. One from an old position on a straight line deserves a phone call first.
When to withdraw an ETA
The rule that people push back on: when the position is old enough that you no longer know where the truck is, the ETA should be withdrawn, on the board and on the customer's page. Not greyed out, not marked “estimated,” withdrawn. A stale number is worse than no number, because a receiver reads it as a plan and a dispatcher reads it as reassurance. The threshold is yours to set; LoadSignal ships with an hour, and the playbook for a truck that goes quiet covers what happens next.
The same applies to a route that came back as a straight line because the routing provider was down or over its quota. The board should draw it dashed and call it a straight-line estimate, never present it as the road, and the ETA built on it should carry the same warning.
Telling the customer a time
A receiver does not want the ETA; they want to know whether to have a crew at the door at 6 a.m. Tell them a window, not a minute, and tell them what it rests on: “Between 5:30 and 6:30 a.m. The driver is 210 miles out and has the hours to make it.” When the number moves outside the window, tell them before it does, with the new window and the reason. A customer who hears “the driver took his break at Cookeville, now looking at 7 to 8” at 9 p.m. has time to move the crew. One who finds out at 6 a.m. does not, and remembers it.
LoadSignal builds its ETA from a road route planned for the load's truck, the driver's remaining hours where the ELD reports them, and the age of the last position, and marks it with the confidence those three inputs justify. The system estimate is shown beside the driver's own reported ETA, never blended into it, and the estimate is withdrawn when tracking is lost. The real-time load visibility guide covers where the positions come from, and the detention guide covers what happens once the truck arrives.