If you have a DVM (Digital Volt Meter) I would do the following:
First check for battery voltage (12-14) across the leads with Key Off.
Then Check for battery voltage with key ON.
Then check for voltage with the lights on.
If voltage present , I would either trace them back and disconnect from voltage source OR cut the ends off and tape them up individually with electrical tape.
If No voltage in any condition , switch meter to Ohms If you are reading below 100ohms they probably go to a lighting circuit (which would support the tow behind)
If they read open or higher than 100ohms , anybodys guess.
Either way if you are not going to use them ( cut the ends off and tape them up individually)