spatial density estimation of "lines"

Dear all,
I am trying to compute a spatial density estimator where the samples are not points but lines. The usual kernel density estimators will not work very well, because of their fixed xy orientation. I am imagining adding up many "ridge" like density contributions that are aligned with the line. (instead of Gaussian blobs). 
Does anyone know about algorithms or maybe even R functions that would compute such a density ?

Thanks!

Markus