DB: Lindenthal, in the 1920s, was clearly the senior bridge engineer in the country. He had created a series of major bridges, beginning with the Smithfield Bridge in 1883 and coming up to the Hell Gate and this, and the great truss bridge over by the Ohio River. These were major designs, which, all of which received awards from the American Society of Civil Engineers. He was not a bureaucratic person in the sense that he was not an officer of the American Society of Civil Engineers. He wasn't active in that sense, but he was certainly revered, and his technical competence was beyond dispute. Therefore, it was of great value for Ammann to have worked with him, but all great bridge designers need to work to some extent alone. To be in the shadow of Lindenthal would not have led Ammann, I believe, to his great works. Therefore, a break was essential regardless of what the means for it would have been. It's perhaps possible to conceive of Ammann never having left Lindenthal and staying with him in some sense, and then it seems possible that he would not have created his great works. So the chance to do that was of great benefit for Ammann. It was also personally quite difficult for him because he had originally hoped to talk Lindenthal into a quite different design for the Hudson River, or the North River crossing. It was Ammann who saw clearly that the bridge had to be lighter and more focused on automobiles and less on railroads. And Lindenthal was essentially tackling an almost impossible problem: designing a suspension bridge for railroad traffic. Now, of course, it's technologically conceivable that one can do that. Roebling had done it with his Niagara River Bridge, but, of course, the trains had to go exceptionally slowly, 3 to 5 miles an hour across. It was not a reasonable modern solution, although it was a reasonable solution in Roebling's day. But since that time nobody had succeeded in doing that in a major bridge, so Lindenthal was fighting a difficult problem right from the start. And it, I think, took Ammann a while to realize that it was impossible for Lindenthal's vision to actually, to succeed. So that this break was difficult for Ammann and yet, I believe, it was essential.

DB: Ammann himself agonized over it and particularly difficult for him was the fact that he had no real job. He didn't go immediately with some commission in hand, as many people do when they start a new business. He had nothing, and so it was really a risk for him and this made it unusually difficult, I think.

DB: Ammann's proposal is the first major bridge to be built essentially for automobiles. In his original designs, of course, he did include the idea of a second deck for rapid transit. And that was the standard way at the time. The Manhattan Bridge, the Delaware Memorial Bridge, now the Ben Franklin Bridge, had been conceived that way, but in both of those designs the idea of automobiles as the primary vehicle, or automobiles and trucks as the primary vehicles, was not yet fully addressed. And it was Ammann who, as far as we can tell, was the first person seriously to address that problem, what should be the proper loading on a bridge, which has just cars and trucks. So he made a careful study of this and it was on this basis that he determined that it was reasonable to use what seemed to the profession at the time, or at least seemed to those who looked at the profession at the time, to have been quite a daringly low load. And yet today we now accept that load as being the reasonable one for all bridges.

DB: It was a certain leap for Ammann to take to move to this very much lighter bridge when his boss, Lindenthal, was so committed to a heavy bridge focused on railroad traffic. Ammann began to see in the early '20s that that was not a practical solution, that it was far too expensive, that it was in the wrong location because it would disrupt the city streets to build this huge bridge with big approaches, dumping all kinds of traffic into the middle of the city. So it was a dramatic and daring idea and it goes together with what was happening at the Port Authority, because the Port Authority had been constituted to solve the railroad problem. And in the early '20s, it was grappling with that problem unsuccessfully. And so there's an element, one might say, of the right person at the right time, in this case, but Ammann saw clearly that that was the case. And at the same time there's another factor here which can't be neglected, and that is that as the more Ammann thought about the impracticality of the Lindenthal design and the more he tried to think of what would be a practical design, the more he became emotionally attached to this new form that he saw possible, this lighter, more elegant form. And it was this emotional attachment which, I am convinced, was behind what he then did.

DB: So it was not so much a clear, careful traffic analysis or a rational understanding of how cars were going to take over railroads. Very few people could see that at that time and the railroads were still very powerful. Cars were still mucking around in unpaved roads. They were still a novelty in the early '20s. So I think that the most important thing for Ammann was the fact that here was a new project of unprecedented size that he could do himself and that it would be not just utilitarian, but beautiful. So I think that was, in a way, driving all of these other issues, but coming from the tradition of Lindenthal and engineering, that is inseparable of very careful analysis of everything you could think of. He made analysis that discussed the traffic questions, the economic questions, the technological questions. All of those were important, so it was not just this emotional wish to do it that was there, and I believe very important, but along with that comes this long experience because, after all, Ammann was by now not a young man. He had already had lots of experience and was coming with that. And that combination of the experience, the sensitivity to detail working out of an engineering project, combined with the emotional charge of a new form of great elegance that is what carries engineers out into the risky world of entrepreneurial behavior.

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