Most trucks have a solid state controller for running lights and flashers. The use of LED for them is a matter of current draw and less is better.
There is a new White LED out that actually has four substrates in one cell. It is very bright and is currently being used by some cities to convert from florescent.
And there are four cell LED fog lamps we are using on some vehicles that are as bright as incandescent.
Solid state lighting is moving fast as the world doesn't want to pay for light.
