In this paper, the viscoelastic behaviour of bitumen is studied and an appropriate and suitable constitutive equation is identified to describe its rheological behaviour. First, the generalised Maxwell model has been utilized to represent the relaxation modulus of bitumen and found to be in excellent agreement with experimental data over a wide range of temperatures (-30 degrees C to 90 degrees C). Furthermore, the time-temperature superposition principle was found to be applicable over this temperature range. The K-BKZ constitutive equation has been shown to represent accurately the rheological properties of bitumen. Analysis of experimental results revealed that either the Papanastasiou or the Marucci form of the damping function can be used in the K-BKZ constitutive equation. Moreover, the damping function was found to be independent of temperature (0-50 degrees C). (C) 2012 Elsevier Ltd. All rights reserved.