6. Performing Organization Code 7. Author(s)

This report documents procedures and results associated with the development of improved guidelines for driveway to entrance ramp spacing along freeway frontage roads. The analyses utilized in this research consisted of operational and crash/safety assessments — both of which were based upon field data specifically collected as a part of this research project and/or historical data. Several locations in the San Antonio and Austin, Texas, areas were utilized as field sites in this study. The results of the research indicate that an adoption of new “desirable ” guidelines should be pursued to accompany the current guidelines — the latter of which it is suggested be retained as “absolute minimum” spacing guidelines. The new “desirable ” guidelines serve to double the distance in existing guidelines in relation to both upstream and downstream placement of driveways in relation to entrance ramps. This change specifically entails going from an absolute minimum of 100 feet to a desirable spacing of 200 feet upstream of the ramp and an absolute minimum of 50 feet to a spacing of 100 feet downstream of the ramp