A top sustainable transport charity has advised those looking for an environmentally-friendly way to travel to opt for a bicycle.Sustrans reports that as well as being good for the body and fun, it is around 70 times more energy efficient than the average car.It notes that - aside from walking - cycling is the least polluting method of travel, with two kilogrammes of carbon saved for every short journey taken by bike instead of car.A spokesperson for the charity said: "Cycling helps children grow up fit and healthy, and introduces them to the wider world and the adventure it holds."Cycling gives young people freedom and mobility."He added that ten bikes can be parked in the space taken up by one car.National Bike Week, supported by Sustrans, will run from June 14th to June 22nd this year and hopes to promote cycling as a source of fun and fitness.