During testing in 2009 it was found that the new ETR 610 trains were too heavy for the main Gotthard route from Zurich to Milan for which they had been ordered. The weight of the train influences the permitted cornering speed due to forces on the track – the heavier the train the slower the cornering speed allowed. It was found the new trains would have to run so slowly that traditional trains without tilting technologies would be just as fast, thus calling the whole project into question.