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This paper is devoted to the proof of the well posedness of a class of ordinary di® erential equations (ODEs). The vector¯eld depends on the solution to a scalar conservation law. Forward uniqueness of Filippov solutions is obtained, as well as their H older continuous dependence on the initial data of the ODE. Furthermore, we prove the continuous dependence in C of the solution to the ODE from the initial data of the conservation law in L . This problem is motivated by a model of tra± c°ow.

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Consider a general strictly hyperbolic, quasilinear system, in one space dimensionwhere u → A(u), u ∈ Ω ⊂ R N , is a smooth matrix-valued map. Given an initial datum u(0, ·) with small total variation, let u(t, ·) be the corresponding (unique) vanishing viscosity solution of (1) obtained as limit of solutions to the viscous parabolic approximation u t + A(u)u x = µu xx , as µ → 0. We prove the a-priori boundfor an approximate solution u ε of (1) constructed by the Glimm scheme, with mesh size ∆x = ∆t = ε, and with a suitable choice of the sampling sequence. This result provides for general hyperbolic systems the same type of error estimates valid for Glimm approximate solutions of hyperbolic systems of conservation laws u t + F (u) x = 0 satisfying the classical Lax or Liu assumptions on the eigenvalues λ k (u) and on the eigenvectors r k (u) of the Jacobian matrix A(u) = DF (u).The estimate (2) is obtained introducing a new wave interaction functional with a cubic term that controls the nonlinear coupling of waves of the same family and at the same time decreases at interactions by a quantity that is of the same order of the product of the wave strength times the change in the wave speeds. This is precisely the type of errors arising in a wave tracing analysis of the Glimm scheme, which is crucial to control in order to achieve an accurate estimate of the convergence rate as (2).