in terms of tractive effort and drawbar horsepower, prr s1 was the most potent reciprocating steam locomotive ever built for passenger service. starting tractive effort calculated in the usual way (85% mean effective pressure) comes out , but the engine used 70.6% limited cutoff (presumably to increase port openings at short cutoff), so the railroad claimed a correspondingly lower tractive effort. during a test run between chicago, illinois and crestline, ohio in december 1940, s1 managed to reach on level track with 1350 tons passenger stock behind her, which was equal to 24 postwar lightweight passenger cars. in this test run, s1 also achieved an average speed of , which was 27% faster than the average schedule speed of the route. some publications from germany stated that s1 was able to reach in other road tests during the late 1940s with a lighter load behind her, but prr never claimed this record. on apr 19, 1941, during an excursion run organized by the detroit railroad club, s1 reached on the route between fort wayne and chicago.