20 C.F.R. § 330.4
The phrase "last railroad employment in the applicable base year," as used in § 330.2(a) of this part, means generally the employee's last "service performed as an employee," within the meaning of section 1(g) of the Railroad Unemployment Insurance Act. If an employee did not actually perform any service as an employee in the applicable base year (the calendar year preceding a benefit year) but did receive qualifying compensation such as vacation pay or pay for time lost for days in such base year, the Board will consider that his or her last railroad employment in the base year was the employment on which the qualifying compensation was based. The daily rate of such compensation shall be deemed to be the employee's daily rate of compensation for purposes of this part. If an employee's last railroad employment in the base year was casual or temporary work and was performed while on furlough from other base year railroad employment, the Board will disregard the daily rate of compensation paid for the casual or temporary work if such rate of compensation produces a daily benefit rate lower than the daily benefit rate based on the daily rate of compensation for the employment from which the employee was furloughed.
20 C.F.R. §330.4