Simulate light bulb load with LED
You present this as if your design solution needs to be much smaller, use LEDs, but still dissipate 480 W and behave the same as a bunch of 15 W lightbulbs?!?
In order to properly test a traffic light controller that is going to control lightbulbs, you will need lightbulbs for testing.
Why?
Because a lightbulb, when cold, will have a low resistance and will draw a current peak when switched on. You cannot easily do the same with a LED.
LEDs are fundamentally very different beasts than lightbulbs. LEDs need a low voltage. LEDs cannot work on a constant voltage, they need a (somewhat) constant current.
You can put LEDs in series to increase the voltage and use all kinds of circuits to make them work on 230 V AC. But from the controller's perspective, such an emulated load will look very different from a real lightbulb.
You could use resistors to emulate the lightbulb. Then the resistors would dissipate most of the power (use power resistors, heatsinks are optional depending on what resistors you choose) and the make a simple circuit (capacitive dropper) to power an indicator LED. But realize that the resistors do behave differently from a lightbulb as resistors have a constant resistance, lightbulbs do not.
It all depends on what level you need to do the testing of your controller.
If you only need to be able to test that the lights go on/off properly, add LEDs in your design to monitor the signals that go to the stage that drives the lightbulbs.
If you're using TRIACs / Thyristors to switch the lightbulbs then using a low power LED lamp might not work as the hold current could be too low. Then adding load resistors to make more current flow could suffice (maybe less than 15 W also works).