With only one master, collisions are not expected, since slaves only transmit when requested by the master. It is the master's responsibility to ask the slaves in an educated manner, one by one.
Even in multimaster configurations, the use of additional wires would be avoided. There are many protocols used for this purpose: for this: Carrier sense multiple access (CSMA), the same plus collision detection (CSMA/CD), etc.
I think that RS485 is suitable for your application: It is simple and robust, and works fine in noisy environments. If you are new with RS485, search for RS485 in the forum. What bit rate will you use in your system?. Remember that for high speed and long distances you must use a good RS485 cable and put suitable terminations at its ends.

Alfredo.