I'm walking the 1/2 marathon in January. The last time I did this was in 2005 and it looks like things are a bit different from back then when everyone started at once (and the 1/2 and full marathon were on the same day). Does each corral have its own start time? Since I'll be in the last corral, am I correct in thinking that although the race starts at 5:30, we won't even start to walk until 6:17? But we still have to be on the bus by 4:00 a.m.? Thanks for your insight. 
