The following actions all cause a cars lights to switch off.

1) Getting out of the drivers door.

2) Opening the door on the passengers side.

3) Getting out of the passengers door.

This makes it impossible to get out of a car and use the cars lights for illumination.

Be the only person in the car at night.

Put the lights on.

Perform any of the above 3 actions.

Don't know if relevant but I have mapped actions ( door open ) set to mouse 5. Lights to 'G' and move seat to mouse 1.

This started from the first 1.29 release iirc.

Before that it was possible to leave a cars lights on for illumination or to help locate a car at night after some looting.

Cars light should stay on until switched off by the driver.