Love them or hate them, bendy buses are impressive. You see one coming around a corner looking like an ordinary bus, then comes the articulated bit and then more bus. Now the unveiling in Dresden, Germany, of the AutoTram Extra Grand raises the bar with a bendy bus that’s more like a bendy train. With three sections, measuring over 30 meters (100 ft) long and a passenger capacity of 256, it’s the world’s longest bus.

Urban mass transportation is an exercise in paradoxes. The very things that make it so necessary make it so difficult. Pack hundreds of thousands of people in a small area and moving them around becomes a major problem. Unfortunately, that very population density doesn’t leave much room for roads, rail lines or other systems. One solution is that if the available systems aren’t suitable, then borrow technology from one, add it to another to create a third – like the AutoTram.

This is the approach that created the AutoTram Extra Grand. A joint venture of Fraunhofer IVI, the Technical University Dresden and Wittur Electric Drive GmbH, the Autotram isn’t just a standard bendy bus with an extra section tacked on. It uses train technology, adds it to buses and makes them suitable for urban areas where trains are not a practical solution to transportation problems.

With four guided axles, three controlled by an electrohydraulic actuator system, the AutoTram can be steered forward and backwards like a standard-size bus while computer controls handle the steering of the individual sections so that they follow along like railway cars on a track. This system works so well that drivers don’t even need a special license to operate the Autotram.

A hybrid electric vehicle, the AutoTram Extra Grand has a seating capacity of 96 and with standing capacity can carry a total of 256. Power comes from two diesel “power packs” consisting of six and eight cylinder generators putting out 220 kW and 235 kW respectively. These are backed up by 420 kW supercapacitors and 120 kW lithium-ion batteries. Fraunhofer IVI has also equipped the AutoTram with control algorithms to ensure efficient energy management and allow the giant bus to travel up to eight kilometers (5 mi) on battery power alone.

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