Abstract. For a perfect eld k, we use the techniques of Bondal-Kapranov
and Hanamura to construct a triangulated category of mixed motives over the
truncated polynomial ring k[t]=(t^{m+1}). The extension groups in this category
are given by Bloch's higher Chow groups and the additive higher Chow groups.
The main new ingredient is the moving lemma for additive higher Chow groups
and its refinements.