The 1994 Update of the Highway Capacity Manual (94HCM) included a new regression- based method for analyzing ramp-freeway junctions. An alternative to the method outlined in the 94HCM is the use of a microscopic simulation model such as FRESIM (FREeway SIMulator), also developed in 1994 by the Federal Highway Administration (FHWA). A thorough understanding of the benefits and limitations of both methods is advantageous in freeway analysis. To provide that advantage, the National Cooperative Highway Research Program (NCHRP) devoted its Report 385 to a discussion of both methods. NCHRP called their report "Comparison of the 1994 Highway Capacity Manual's Ramp Analysis Procedures and the FRESIM Model."

The method described in the 94HCM is a regression-based model for ramp-junctions. Possessing an extensive database, it provides valid results; but like many regression-based models, it can model only effects present in the database from which it is developed. The 94HCM model also has limitations for 8-lane freeways. A simulation model such as FRESIM, however, can compensate for those limitations. FRESIM models traffic explicitly, using sophisticated mathematical algorithms to model the complex driving behaviors of each individual vehicle. Nevertheless, FRESIM is not without limitations, notably its inaccuracy in predicting the merging process. For widespread use, FRESIM must also become more user-friendly.