Keep in mind that, as a rule of thumb, air can withstand ca. 1 kV/mm potential before arcing over. A solder mask provides additional isolation, so practically you won't have to increase the clearance too much for a 60 V board. However, higher voltages lead to stronger electrostatic interference with adjacent traces, so unless your 60V lines are DC, avoid running them close to any other sensitive traces or components.
Regarding the current, consider that any trace, regardless its width, will have a certain impedance and thereby cause a voltage drop. If the current or impedance is too high, the trace may heat up too much and in extreme cases result in a fire hazard or a burnout (the copper gets so hot it evaporates, severing the connection).
As a rule of thumb, I set the width to 1 mm/A/oz. For example, to run a 10 A current over a board, use a 10 mm trace on a 1 oz (35 µm copper thickness) board and 5 mm trace on a 2 oz (70 µm) board.