Example surface density profiles of gas (solid, initial value only) and (small+large) dust (dashed, at different times) for each of the three scenarios, illustrating the changing dust surface density distribution due to radial drift. The dip in the gas surface density signifies the gap, in this case at R_gap = 30 au and after 0.1 Myr (red), dust has begun to accumulate in the trap at its outer edge. The traffic jam that occurs in Scenario 1 can be seen in the steep rise in the dust surface density after 0.1 Myr inside the water snow line at ≈0.4 au. The other small steps correspond to changes in the solid fraction at snow lines and the smaller bumps are the accumulation of ices at snow lines due to the cold finger effect.