An extensive experimental program has been carried out to acquire two-phase transient flow data on 420 m long, 77.9 mm dia horizontal pipeline, using kerosene air mixtures. A computer-based data acquisition system has been utilized to obtain rapidly changing and detailed information on the flow behavior during the transient tests. Pressure, in situ liquid holdup, translational velocity and flow pattern changes were monitored at four measurement stations installed along the pipeline. An existing simplified model for predicting two-phase transient flow behavior that uses physically-based flow pattern-dependent mechanistic models has been modified and improved. The resulting set of differential equations is solved numerically utilizing a semi-implicit numerical scheme. Comparisons of the predictions of the numerical model against the experimental data show that the proposed simplified transient model is well suited for simulating several types of transient behavior encountered in two-phase pipelines.