Local speech rate is an emergent field in research on prosody. This paper introduces a syllable duration model based on intrinsic syllable duration properties and local speech rate variations. The proposed model is compared to the observed syllable durations and to a standard model in which durations are normalized according to local speech rate only. This comparison shows that our model is i) robust : significant reduction of the observed syllable dispersion, ii) consistant : this reduction comes with reduction of duration dispersion due to the syllable intrisic properties as well as prominence phenomena.