Don't use the Alt Tangent Basis option, and try exporting with Tan 0, Bin 0. It shouldn't really be happening on those objects though, as they are fairly simple (road is a collection of near-perfect quads for instance).
Keep an eye on your VertexIn vs VertexOut numbers when you use Tan/Bin values greater than 0.0 - you can get a lot of extra verts generated. I think if you're near 1.0 for one or both values, nearly every triangle will get its own unique verts (not good).
