In Germany you bury cables usually directly, minimum 0.3m without or 0.6m with traffic . Cooling is better than in a conduit, so you can uprate them and refer to 15°C external temperature. Furthermore, also in a conduit you will have to use the same cable, as there are no ground water(is often a bit acid) resistant wires. Buried conduits are not regarded as water tight except short distances (< 10m from cellar to cellar) where the conduit is well accessible and has a defined slope.
There are cable types with concentric (PE connected) shield, which are rarely used, as more expensive. Normal unshielded earth type cables (called NYY) are not regarded as dangerous.
And as already mentioned in other threads in German towns usually everything arrives underground and without conduits: phone, cable tv, electricity, gas and water. You are supposed to lay either a coloured information tape or special plastic protection or bricks above the cables.
