In principle, there is nothing stopping PPM flywheel energy storage being used in road vehicles and we would be very happy to work on developing these. However, we have chosen to concentrate on rail systems because:

• Steel wheels on steel rails are more efficient than rubber tyres and so better for the environment
• Repeated studies and experiences show that even when people won't use buses, they will use trams and trains, so the best way of making public transport work to reduce car use is to invest in rail-based systems
• In urban situations, various factors such as that explained below make trams more “comfortable” in comparison with other modes of transport:
  
  "Think of yourself in a car at the traffic lights.  A tram is coming up behind you.  You feel uncomfortable and you instinctively want to get out of the way.  You feel that, in some strange way, you are actually trespassing on the tram's 'right of way'.  The comfortable place to be is on the tram.  With a bus it is the other way around.  The car driver feels he has at least an equal right to occupy the road space and therefore feels quite at ease with the bus behind"
  Garrett Emmerson, Chair of Local Transport Planning Network, writing in Local Transport Today, 15th June 2006