tp.ppp <- as(tp, "ppp")
roads.psp <- as(roads, "psp")
tp.roads <- project2segment(tp.ppp, roads.psp)
network <- points2network(roads, pts.nodes, mapping.method=2, ELComputed=TRUE, longlat=TRUE, ea.prop=(rep(c(0), length=roads.columns)))
graph <- nel2igraph(network[[1]], network[[2]], weight=network[[8]])
plot(graph, vertex.size=3)