Both the engineer and fireman must read the train orders, the fireman being a double-check on the understanding of the orders and the compliance of the engineer to the orders.
Their bid called for the two companies to double-check each other's work, which would have almost certainly caught the polishing error that later caused such problems.
Finally, double-check the statistics by perusing the data, particularly its source, to get a sense of why the audiences surveyed answered the way they did.