Two-dimensional almost-Riemannian structures are generalized Riemannian
structures on surfaces for which a local orthonormal frame is given by a Lie
bracket generating pair of vector fields that can become collinear. We consider
the Carnot--Caratheodory distance canonically associated with an
almost-Riemannian structure and study the problem of Lipschitz equivalence
between two such distances on the same compact oriented surface.
Two-dimensional almost-Riemannian structures are generalized Riemannian
structures on surfaces for which a local orthonormal frame is given by a Lie
bracket generating pair of vector ?elds that can become collinear. We study the
relation between the topological invariants of an almost-Riemannian structure
on a compact oriented surface and the rank-two vector bundle over the surface
which de?nes the structure. We analyse the generic case including the presence
of tangency points, i.e. points where two generators of the distribution and
their Lie bracket are linearly dependent.