Thin web materials are commonly transported through machinery where a process adds value to the web. The flexible web is supported intermittently by contact with rollers. The friction forces associated with this contact are largely responsible for determining the lateral mechanics and dynamics of the thin web transiting rollers in roll-to-roll process machinery. The investigation focuses on cases where slippage between the rollers and web has become substantial and has resulted in a complex lateral behavior of the web. Two methods are presented for investigating the frictional forces and the resulting lateral behavior. The first method employs explicit finite element (FE) dynamic analysis to study the lateral mechanics of the web after steady state behavior has been achieved. This method allows the direct study of the frictional forces. The second method employs Laser Doppler Velocimetry in a novel experimental noncontact technique to examine internal loads within the web, which were influenced by the frictional forces. Both methods are shown to provide results, which agree with one another and with previous analysis. The analyses are used to form a new friction boundary condition between a web and roller that will benefit other analysis methods.