b+w #106 nd filter - am I seeing color cast?

I picked up this filter because I wanted to work on smoother light trails of traffic. I've gone out a couple of times recently, attaching this to my 35mm f/1.4L, just after sunset. I am finding that the headlights are exposing exactly as I would like them to, but the tail lights are much fainter than I would prefer.

I've read that at least the #110 filter has a warm color cast to it. If this does as well, and my CWB correction is why the shot does not look particularly warm (I believe it was 2900 K), would this cause the disappearance of much of the tail lights?

Photo below.

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Your eye sees red light much better than the camera does, regardless of WB. Also remember that manufacturers are starting to use LEDs for the tail lights; while they may show up, they aren't actually really bright. And headlights are supposed to put enough light out for you to see by; tail lights are just supposed to let you see them. Try metering each separately on your car and you'll see.