The answer I have found is both clear and straightforward:

require(maptools)

IloveR<-as(as(readShapeLines(fn="mylinedata.shp"), "SpatialLines"), "psp")

I was hoping someone might be able to point me in the direction of something
like this but I was fortunate enough to stumble across it in one of my many
revisits of the maptools manual.  I find using this in conjunction with the
distmap() and interpolate.im() functions of spatstat to be an
extremely economical way of calculating "distances to nearest..."
(watercourse, road, etc.) using spatial relocation data.

Tyler

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