Every year, experts in freight and passenger mobility gather in Washington D.C. for the annual meeting of the Transportation Research Board (TRB) to talk policy, present technical papers, analyze trends, and wander through an exhibit hall packed with the latest products related to highways, railways, and other modes of movement. TRB's 97th annual meeting proved no exception. Here's a snapshot of some of what went on over a five-day span in the Walter E. Washington Convention Center, located in the heart of the nation's capital.