Conventional Shipping beacons and traffic lights seem to be efficient, although only 1% of the consumed electricity is converted to visible light. Furthermore they suffer from the so-called phantom effect and all the incandescent lamps have to be replaced at least every single year.

LED lights however are made of semiconductor material (as in computer-chips) and convert electricity directly into the desired coloured light (without filtering) with an efficiency of 10%.

They don't suffer from the phantom effect. LED's are insensitive to vibrations. Because a single LED produces only a little light, a signal is made of several LED's. this makes LED signs relatively expensive. The payback time is a few years.

Table 1: Differences between LED and incandescent lights.

LED Lights	Incandescent lights
Light-source consists of 10 to 200 LED's	Single light-source producing white light (krypton or halogen)
LED's produce coloured light directly	A lens filters the required colour
Very high intensity	Intensity normal
No phantom effect	Phantom effect
Very reliable, long life span	Short life span.
Dimmable	Poor dim ability
Energy efficient	Poor efficency, lot's of heat dissipation
Insensitive to vibration	Receptive to vibration, poor reliability
Not yet fully standardised	Standardised
Red light detection is difficult	Easy red light detection
High initial cost	Low cost
LED lights deteriorate gradually At 20% malfunction Lamp is switched-off	Does function or not.
New technology	Common technology
Low maintenance cost	High maintenance cost
Operation temperature dependent	Operation temperature independent