Why the fastest route is not the shortest one
On a quarter of the pairs on our network, the quickest way between two terminals is a longer route. Here is the arithmetic, and why it matters when you are buying freight.
Put Dunmore Quay and Cawdor Point into the routing engine on our network page. It will send the box 746 km. There is a 571 km path and it does not use it.
The arithmetic
The shorter path leaves the rail network for a road link between Halgate and Kelvedon. That means two mode changes: rail off, road on, road off, rail on. Each rail-to-road interchange costs four hours — a lift, a re-plan, and the paperwork that goes with handing a box between two different kinds of operator. Eight hours, to save 175 km, which at 62 km/h is a little under three hours of running.
So the longer route is roughly five hours faster. Not marginally: most of a working shift.
Why this is not obvious
Because maps show distance and invoices show distance, so the instinct is to optimise the thing you can see. What actually determines a transit time on an intermodal network is the number of times the box changes hands. Across all 132 ordered pairs of terminals on our network, interchange accounts for an average of 16% of the total clock, and on 30% of the pairs it is more than a quarter.
What to do with this
Ask a carrier how many interchanges are in a quoted transit, not how many kilometres. A quote with one lift in it and a quote with three are different products even when the transit time is identical, because they fail differently — the three-lift route has three places to go wrong and three sets of gate hours to miss.