While the rear lights are fairly visible on most cars with up to a 5 bike rack, they can be obscured and especially with the 6 bike. And any lights mounted on the rack will still be obscured by the bikes which is why we have the optional light board.
Quality LED lights including a number plate light which is required for night drives, flat plug, can be quickly fitted to the bottom bar of the rack or when fully loaded moved to the wheels of the bikes.