The compressor doesn't have the CFM needed. If you are going to run real train horns (I have nathan K5LAs) you need a crap load more compressor and a minimum of 5 gallons of air depending on how you want to use it. I'm running an Oasis 12V compressor to a 5 gallon tank, mostly for air tools and trailer air suspension but truthfully anything under a 450C Viair compressor would be under whelming for the horns. Figure close to 2,000 dollars for a good setup with big lines, pressure, flow and valves.
For what it's worth I have 3/4" air lines all the way to the horn and valve, when you hit them on the highway people will move out of the way, very effective for those who are inattentive.
