A model of lock failures as manifested by% talls or interferences lock operation. An interference is an occurrence which slows and specified in terms of a logit formulation is presented in this lock operation during a lockage. For more detail see the Corps* paper. Stalls or interferences that correspond to commercial tow User's Manual for Data Analhsis (2). and recreational vessel lockages and that result from lock hardware problems or to testing or maintaining the lock or its equipment are first considered. The expected frequency of such lock stalls) that correspond to commercial tow and recreational failures relative to the number of commercial tow and recreational vessel lockages and that result from lock hardware problems vessel lockages is then explained. These expected frequencies can or to testing or maintaining the lock or its equipment. It then be viewed as measures of reliability or interpreted as the prob- explains the expected frequency of such lock failures relative ability that such failure% will occur on any given commercial tow to the number of commercial tow and recreational vessel lockor recreational vessel lockage. The qualitative results correspond- ages. This can be viewed as a measure of reliability. It can ing to the underlying variables are consistent with expectations.