In March, in the desert between Barstow, California, and Las Vegas, the DARPA Grand Challenge -- where autonomous vehicles must navigate themselves without any input from human handlers -- will make its dusty debut. For our March 2004 issue, writer Joe Hooper profiled some of the groups developing vehicles for the event. PopSci staff photographer John B. Carnett captured some of the trials and tribulations of Grand Challenge hopefuls on film. Here are some of the images that didn't make it into the magazine but that Carnett found particularly interesting.