Rob, timber for the railing and uprights or just railing? If just railing then some nice boxed rectangular tubing would work good for your uprights. Plates welded on the bottom/side to weld to "embedded" plates in concrete and plates on top to lag screw the railing to... If timber both ways then a nice box bracket to slide the vertical timber in to and attach with lags or ?? This box bracket could be welded to concrete plates.
BTW, very nice bridge and abutment!:thumbsup: