Although the Board of Trade forbade this system being used on any future passenger railway, it was used in this case because the trains were experimental and were forbidden to carry fare-paying passengers.
Selvom Board of Trade forbød at dette system blev benyttet på nogen som helst fremtidig passagerjernbane, blev det benyttet i dette tilfælde, da togene var eksperimentale og ikke havde betalende passagerer.