Just when you think you've seen everything in the transportation world, you encounter something different. That happened to me on an infrastructure tour in Cambridge, England, when my guides showed be this guided busway.

The video only shows a short segment of The Busway, but it's fascinating. The wheels of the bus run between grooved concrete slabs along an old rail line. The system also handles drainage without burdening the sewers: Stormwater is absorbed by the ground.

At 16 miles, the Cambridge guided busway is the longest one in the world. Bus speeds can reach up to 55 mph.

A busy biking and walking path runs right next to the route. You won't find railings separating the busway from the trail. There's no honking or flashing lights like you would find in the USA -- just common sense.