Increasing the pedaling comfort and efficiency of the tandem drive train has been the main focus of performance tandem designers, davinci Designs.
So what comprises the independent coasting mechanism or 'ICS'?
"The main component of da Vinci Designs’ ICS is an intermediate drive shaft six inches in front of the rear bottom bracket. The intermediate shaft has two single-speed freewheels on the left side that are independently driven by the cranks at twice the rotating speed and half the torque. On the right side of the shaft, four Hyperglide™ cogs drive the bike. The chain rings are half the size as those on a conventional tandem because of the double rotation of the intermediate shaft. The combination of 12-, 18-, 24-, 30-tooth driving gears equals 24-, 36-, 48-, 60-tooth chain rings."
Read more here.