Signals, tunnels, and ballast requirements.

🚦 Signaling

• Frequency: Signals must be placed every 8 chunks, backtracking from a junction.
• High Traffic: If multiple junctions are close together, signals may be closer, but not closer than 4 chunks (maximum train length).

🌉 Clearance & Materials

• Tunnels: 10 blocks vertical clearance and 2 blocks horizontal clearance on either side.
• Building Rules: Build tunnels if >10 blocks of terrain is above; build bridges if >10 blocks of space is below.
• Ballast: All tracks must lay on top of either gravel, tuff, or light gray concrete.