Q:

How can I force ONLY rail export of goods from a trade port?

I have a trade port with a freight rail terminal, that I use to export processors. 
Because of traffic issues, I do NOT want to export using trucks, especially since the rail capacity is more than enough to export everything.
However, even though I took away ALL delivery truck garages from the trade port, trucks still appear (from the region, I guess) and pile on my traffic problem.
Can I force this trade port to export only using rail?

A:

To force a trade port to only deliver goods using rail connections, simply destroy all of the delivery trucks for that trade port. This can be done by using the bulldozer to destroy the delivery truck garage on the edit building screen.

The suppliers of your trade goods will still be delivered by the building that creates them using their own trucks, but any good that arrive at the trade port will only leave via rail (every 3 in game hours). 

