Roebling mandated that the trains be limited to a maximum speed of to ensure absolute safety. He was confident the bridge could handle faster train traffic, but he preferred a safe operation. In his tests the bridge supported a train, bending under the weight. This was within the maximum load of specified in the design of the bridge. The figure was a conservative estimate. The cables and guy-wires could support , and travel journalist Alfred J. Pairpoint commented that it was normal to see trains pass over the bridge without danger. The bridge shook whenever a train trundled over it, although this had no effect on its integrity. When the frequency of passing trains was high, the trembling was noticeable to travelers on the lower deck and proved uncomfortable to some; writer Mark Twain noted, "You drive over to Suspension Bridge and divide your misery between the chances of smashing down two hundred feet into the river below, and the chances of having a railway-train overhead smashing down onto you. Either possibility is discomforting taken by itself, but, mixed together, they amount in the aggregate to positive unhappiness." Despite such commentaries, thousands of people crossed over the bridge safely every day.