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48 hour test. The 48 hour test determines if stray current or stray voltage exceeds the preventive action level at selected locations over a 48 hour period. The 48 hour test demonstrates whether the primary or secondary sides of the system have a specific impact on the recorded current or voltage at a specific time of day. The results of the 48 hour test may be highly indicative of the presence of stray current or stray voltage.

Source: 42 SDR 174, effective June 21, 2016.