Articulated trains, in which passenger cars share “trucks” (wheel and axle assemblies) with the adjoining cars, improve average speed, passenger comfort and safety. While this configuration sacrifices some capacity per train length and results in higher axle loads, it provides advantages on rough, heavy-haul freight track.
Faster through curves
With individual cars, whether they are independently coupled or semi-permanantely coupled, each car rides through a curve with independent motion, exerting its own forces against the outer rail. Shared trucks lessen lateral stresses on the roadbed as each car pulls the following car through a curve. The result is higher speeds through curves.
Railroad wheels are heavy. A single 36-inch rail wheel can weigh more than a ton. Shared trucks reduce the number of wheels and the weight of the train, letting trains accelerate faster and reducing wear on the track.
The articulation joints cause the ride to be much smoother because each car isn’t bouncing around on its own. Because the car ends do not hang over the truck, the effective width of the train through curves is reduced and articulated trains can be as much as 8” wider than conventional trains for the same track and tunnel profiles. This allows for wider aisles and seats, improving comfort.
Tilting trains lean into curves, much like a cyclist does, reducing the feeling of side-to-side forces in sharp curves. This allows trains to travel faster on older, curvy track while maintaining passenger comfort. Switching to tilting Talgo trains on Amtrak's Cascades corridor in the Pacfic Northwest cut 30 minutes of travel time from the 150 mile trip.