We discuss different notions of
continuous solutions to the balance law
extending previous works relative to the flux
f(u)=u2. We establish the equivalence among distributional
solutions and a suitable notion of Lagrangian
solutions for general smooth fluxes. We eventually find that continuous
solutions are Kruzkov iso-entropy
solutions, which yields uniqueness for the Cauchy problem. We also reduce the ODE on
any characteristics under the sharp assumption that the set of inflection points of the flux
f is negligible. The correspondence of the source terms in the two settings is a matter of the
companion work
[2], where we include counterexamples when the negligibility on inflection points fails.