The 2020 review used a simplified two-route freight account. Six thousand US short tons travelled one hundred miles, and four thousand short tons travelled four hundred miles. The correct sum was 600000 plus 1600000, or 2.2 million short-ton-miles. A proposed calculation averaged the two route distances to 250 miles and multiplied by the combined ten thousand tons, producing 2.5 million instead.
The sponsor liked the shorter calculation because the distance average was easy to explain. I asked the team to keep each weight paired with the distance it actually travelled. The routes did not carry equal weight, so their unweighted mean distance could not stand in for the weight-based calculation. The corresponding weight-weighted distance was 220 miles, not 250. The account used US short tons of 2000 pounds, not metric tonnes.
We allocated US$2.2 million to the broader data work establishing the weight-distance basis and its source relationships. For this reviewed example, the calculation retained the two contributions before aggregation. We documented the unit and scope rather than allowing the familiar word ton to conceal a different mass convention. The response corrected the freight measure; it did not change either route, the cargo moved or the physical distance travelled.
The result also supplied no emissions, cost or productivity improvement. Those questions would require additional inputs and suitable methods under their respective responsible owners. A smaller corrected transport-work figure cannot by itself be presented as fuel saved or a more efficient network. The cost of the decision was abandoning an appealing shortcut and explaining why two apparently reasonable summaries disagreed.
I would preserve paired quantities in the initial analytical specification, especially when the final measure depends on their product. Aggregating each side separately can discard the relationship the calculation needs. The example is deliberately simple so that a senior reader can examine the difference directly, without mistaking a measurement correction for an operational achievement.