Board Thread:Questions and Answers/@comment-50.53.101.152-20130408010537/@comment-24.42.184.89-20130413231029

You can spawn in the item "Upgrade: Creative Mode" ID: 548:14 to test out carts in creative mode.

The item has no recipe and so can only be spawned in. It makes carts build at 10,000 times normal speed and for no fuel cost.