Five days after Hurricane Katrina struck New Orleans, a convoy of 142 air-conditioned school buses from the 209,000-student Texas district rumbled to life. Loaded with food and bottled water, staffed by 350 school employees, and accompanied by bus-repair trucks and a phalanx of school police cars, the yellow buses traveled all night to reach the Crescent City, some 350 miles away. According to public-safety and transportation experts, the work of Houston's school buses, drivers and other employees in the response to Hurricane Katrina and Hurricane Rita illustrates just how important a role both can play in mass evacuations from natural disasters. However, experts comment that exactly how officials plan to use school buses in emergencies--and how effectively those plans are followed--can vary greatly among states and even within states.