The PPM mode has many inherent advantages when used in a tunnel environment:

• When powered by intermittent electrical supplies charging the flywheel, there are no emissions and no need for a continuous power supply.  Therefore ventilation and maintenance requirements are reduced.
• When powered by internal combustion engines, emissions are lower than diesel trains by virtue of the small size and more efficient operation of the engine, lessening the ventilation requirement and allowing self-powered PPM vehicles to operate in tunnels where traditional diesel vehicles are unable to.
• With no requirement for continuous electrification, the harsh environment typical of tunnels does not affect the power supply.
• The flywheel energy storage system allows regenerative braking, reducing heat build-up and brake material particle production and so lessening the need for ventilation and maintenance.

Return to FAQ index page