This paper presents a field experiment on monitoring of reflective cracks in highway asphalt overlay using a Brillouin
scattering based distributed optical fiber sensor. With wheel loading above the joint of existing underlying pavement,
the distributed strain of the overlay near the joint was examined. An initial crack was evaluated and predicted from the
measured strain distribution. Then the progress of the reflective crack was investigated based on monitoring of the strain
distribution of the overlay and the underlying pavement. Within the measurements at three typical times, the contribution
of the wheel loading and the asphalt shrinkage induced by the temperature variation are all analyzed and compared.