Hello everyone.
I want to show you my engineers project. Intelligent lightning system in tunnel using ultrasound ranging sensors HC-SR04. Lights are steering by 6x WS2811 and FastLED library. It’s sometimes blink in other part but this sensors is not compatible with this type of project.
Big thanks to Daniel Garcia 
Regards and Enjoy
http://www.youtube.com/watch?v=dzbWSt6CSJQ
HC-SR04 are difficult.
a) they need a precise timing what is not a good choice in combination with WS2812
b) In a tunnel you get reflections of ultrasonic beams
I have used IR Sensors https://www.pololu.com/product/2474
With the enable pin you can neatly switch them on and off to avoid interference.
Yes, I know, but ultrasonic sensor swas requirement in this project. I had idea with simple IR LEDs but client is not agreed with that 