Hey Frogger,
Deadhead is the pitance your carrier affords you to aid in the cost of "authorized" relocation to a freight zone, insignificant at best but every little bit helps. Accessorial pay is for the warm and fuzzy touch or when you are required to do somthing other than haul freight..IE Inside pick up or delivery, liftgate, pallet jack, pad wrap, multi stop or pick up to name a few... New england pay and or NY city pay is common as far as I know but I have only worked for 2 carriers and cannot speak for all, it is paid to help offset the higher cost of tolls (and aggravation). Hope this helps
Mike and Cyn