The format is very easy. Try to do it yourself.
you need to create a mesh using Createmesh, then CreateSurface(mesh), then AddVertex the number of Vertices (x,y,z,u,v and normals every line) as defined in the header, then use Addtriangle to use the previously created Vertices by Index to create a number of Triangles.
That's all you may also want to PaintMesh the mesh with the LoadBrush'ed texture file as defined in the file header, as well as EntityAlpha for the Opaqueness value.
Probably there can be multiple meshes in one file (see first parameter "Road Count"), not sure of that.
To read the file you may use
re=OpenFile("mesh.asc")
num_roads=readline(re)
road_name$=readline(re)
road_texfile$=readline(re)
road_opaque#=readline(re)
road_verts=readline(re)
for i=0 to road_verts-1
lin$=readline$(re)
; parse line for x,y,z,u and v and use AddVertex with it
; Also parse the normals (nx,ny,nz) and set them for this vertex
next
road_tris=readline(re)
While not EOF(re)
lin$=readline$(re)
print lin$ ; dump to screen for debugging
; here you may parse lin$ for indexes, they come in groups of 3, each group makes a triangle, using Addtriangle with it.
wend
closefile re