The Swiss are among the most environmentally conscious people in the world and are willing to back their convictions with money: the Basle-Milan tunnel plan was approved at referendum, despite the estimated $13.3bn cost. The planners aim to achieve a total ban on lorry transit traffic by 2004, although some argue that a ban will not be necessary as lorries travelling on trains will cut two hours off the Basle-Milan journey. The Swiss are keen recyclers and taxation is used to encourage this. A carbon dioxide tax was also proposed in 1994.