A recent experiment by Shahar et al., on the phase transitions between
quantum Hall states and the insulator, found that the current-voltage
characteristics in the two phases are related by symmetry. It was sug
gested in this work that this is evidence for charge-flux duality near
quantum Hall transitions. Here we provide details of this analysis. W
e review some theoretical ideas on charge-flux duality in the composit
e boson description of the quantum Hall effect, and interpret the data
as implying that this duality is asymmetry in the transition region a
nd that the Hall response of the bosons vanishes. We observe that dual
ity for composite bosons is equivalent to a particle-hole symmetry for
composite-fermions and show that a Landauer analysis of transport for
the latter allows a possible understanding of the reflection symmetry
and Wall response beyond the linear regime. We note that the duality
interpretation supports the scenario of superuniversality for quantum
Hall transitions outlined by Kivelson, Lee, and Zhang. Finally, we dis
cuss how to search for the duality at other transitions in the quantum
Hall regime.