A traffic operational field study conducted on an urban freeway in Dallas, Texas, is described. Major signing modifications were made to the freeway guide signing by state forces exogenous to the research effort. Before and after study data on lane volumes, lane changes, and erratic maneuvers were collected and evaluated. Some specifics and a few general conclusions and recommendations are offered. The operational field study was conducted along westbound I-30 near downtown Dallas. The before study was conducted during 1977 and the after study in 1979. During this period, the freeway guide signing system was updated to 1970 Manual on Uniform Traffic Control Devices standards. Operational studies of volumes, lane changing, and erratic maneuvers were made to determine what effects might be attributed to the signing and what changes, if any, occurred as a result of these changes. Some positive operational changes were noted, but the causal relations were clouded by the fact that the Dallas-Fort Worth Turnpike was made into a toll-free road (I-30) between the before and after studies.(Author)