This should be a fairly simple thing to add. Have traffic react to silent lights pretty much the same way as they do to lights with a siren. The only difference would be that there's a small probability that each AI vehicle will ignore the lights because the driver didn't notice them, say about 20%.
why not some threshold based on your angle and distance relative to them, altered by an "attentiveness" coefficient? that way some cars won't initially notice you, but suddenly will once you get much closer to them.
