As NASA looks to replacing the aging shuttle fleet, there appears that they might have a serious weight issue.
Their new Ares V cargo launch system will (when combined with the transporter and launch tower) weigh in at a hefty 10.9 million kg. The problem is that the crawler road may not take the load. The shuttle in comparison is "only" 7.7 million kg.
I took this picture when I visited the Kennedy Space Center a few years ago and we’re talking a serious piece of road work here. 6.8 km long and 40 m wide and made up of special river rock, any work to make it capable of bearing a higher load would be very expensive indeed.