1849-1850 Royal Commission bridge safety factor study

The Commission asked Charles Fox and other bridge designers what safety factor to use; answers ranged from 3 to 7; the Commission chose 6. Used to anchor the 150-year safety-factor trajectory (6 → 1.67) at the section's pivot to modern practice.

In 1849, the Royals [Royal] Commission in Britain asked a bunch of bridge designers how big safety factors should be. They were designing bridges. They'd designed a girder; they hadn't really worked out all the formulas like we have now. They might just put the girder across two pieces and load it up with 10,000 pounds of something and see if it breaks. They asked some of the big names in the industry at the time — Charles Fox the engineer, Crystal Palace, others. One came up and said, "Well, I think three." Another said seven. The Commission came up and said, "We're going to use a safety factor of six." So in 1850 we were using structural safety factors of six.