It's unclear from your question if you're more concerned with your traces generating EMI/RFI (creating interferance & possibly failing FCC compliance), receiving interference (causing unwanted/undefined circuit behavior), or inter-trace interference (one trace's signal interferes with its neighbors).
Fortunately however, if you were to split your signals into paired traces using differential signalling, you can reduce all three unwanted behaviors.
Other potentially useful approaches:
Placing your 4 signal traces 'interleaved' between 5 ground traces will give some interference improvement (emitted, received, and inter-trace), though somewhat less improvement for emitted & received EMI/RFI than "true differential" signalling.
'Interleaving' 4 differential pairs between 5 ground traces (pattern: GND/S1+/S1-/GND/S2+/...) would further improve inter-trace interference performance over differential pairing alone.
Placing your data lines on an internal layer of a multiplayer PCB (with or without differential pairing &/or ground trace interleaving), with ground planes above & below will provide a high degree of shielding for emitted & received EMI/RFI.