Context: Motors have very little room for electrical insulation so they generally have low voltage ratings. Because transformers (prior to the development of power electronics) cannot step down DC voltages, trains were supplied with a relatively low DC voltage that the motors can use directly. The most common DC voltages are listed in the previous section. Third (and fourth) rail systems almost always use voltages below 1 kV for safety reasons while overhead wires usually use higher voltages for efficiency. ("Low" voltage is relative; even 600 V can be instantly lethal when touched.)

Question: Why do motors have little space for insulation?
Answer: low voltage ratings

Question: What is most common volatage range used by railway system?
Answer: below 1 kV

Question: Why 1kV voltage is almost always used by rail systems?
Answer: safety reasons

Question: Which system uses higher voltages?
Answer: overhead wires

Question: Is "low" voltage used by trains safe for people?
Answer: lethal

Question: How many volts can be considered nonlethal when touched?
Answer: Unanswerable

Question: Motors have a lot of room for electrical what?
Answer: Unanswerable

Question: What can step down DC voltages?
Answer: Unanswerable

Question: Fifth (and sixth) railsystems use what voltages for safety reasons?
Answer: Unanswerable

Question: What has high voltage ratings?
Answer: Unanswerable