Hi,

I'm building a PIC-based ranging system.
I need to measure the distance between moving vehicles and have some
problems doing this.

The distance can vary from 0 to say 150-200 meters (more or less)
I've seen some SONAR-designs doing this, but not in these distances...
My idea is to use one (probably several) 40 kHz transmitter(s)

Oh yes, the field must be quite narrow (to not detect cars in other lanes).
Perhaps LASER would be a better choice?

Does anyone have experiences in this field?

Cheers

/Anders