It seems that bridge designers have been dissatisfied with the appearance of bridges for as long as bridges have been designed.
Certainly in the twentieth century, as the divide between the disciplines of architecture and engineering became clearer, it has been a persistent preoccupation. In 1912, Henry Grattan Tyrrell published Artistic Bridge Design: A Systematic Treatise on the Design of Modern Bridges According to Aesthetic Principles, opening his preface with the words: "A lack of artistic treatment is the greatest fault of American bridges". Tyrrell cited various reasons for poor visual quality of bridges, including price competition, lack of architects' involvement, legal hindrances, but top of his list was simply that engineers were not taught about aesthetics, and little or no literature was available to assist them. Tyrrell's book therefore extensively presented examples of good design, alongside clear guidance on what did and did not work well.
More recently and most notably, Fritz Leonhardt's Brücken (1982) offered a well illustrated survey of bridge design accompanied by a framework of ten key issues which together form a good basis by which designers can evaluate their own work.
Concern over a lack of attention to the visual aspects of bridge design has surfaced periodically in Britain. In 1964, the Ministry of Transport published The Appearance of Bridges, setting out broad principles such as expression of function, relationship to context, proportion, simplicity etc, and suggesting how they could be applied to common types of highway bridge. In 1994, the MoT's successor, the Highways Agency, made aesthetic considerations mandatory in their standard BA41 (latest version BA41/98) The Design and Appearance of Bridges, supplemented with an excellent companion book The Appearance of Bridges and other Highway Structures (1996).
Interest in bridge aesthetics has increased in the USA in recent years, including the establishment of a sub-committee of the Transportation Research Board. As well as their bridge aesthetics website, the TRB published the wide-ranging survey Bridge Aesthetics Around the World (1991) and a Bridge Aesthetics Sourcebook (2010).
Frederick Gottemoeller has been prominent in these efforts to raise American bridge design standards, and his book Bridgescape (John Wiley and Sons, 276pp, 1998) is an excellent source of good sense. Gottemoeller's view is that bridge aesthetics is to some extent objective, that engineers need to play a key role in improving the appearance of bridges, and that they can do so by learning aesthetic ability. His book is targeted not at "iconic" or "landmark" structures, but at the everyday, and most particularly at American highway bridges.
Most of Gottemoeller's key guidance is well illustrated with simple sketches and relevant photographs, and often couched in terms of simple geometric rules, such as relating abutment height to end span length on multi-span viaducts. These are ideal for dunderhead engineers, who love rules and formulae, but behind the numbers there is a drip-drip-drip feed of deeper aesthetic principles - proportion, rhythm, the distribution of material to define the space that surrounds it. Readers who persevere seem likely to imbibe an intuitive visual understanding alongside what seems to be simple and algorithmic.
Bridgescape ranges far beyond being a simple manual for use in better distributing lumps of concrete. It encourages readers to come to terms with their personal aesthetic responsibilities, and gives them a simple design language to make their journey less painful. It offers plenty of real-world examples, both good and bad. It tackles issues of cost, and discusses how design engineers can collaborate with others - especially with the general public, that perennial bugbear of the American design process.
Some of the advice is local or specific to certain types of bridge, but most of it is broadly useful. It's one of the books on bridge aesthetics where I can remember the content most clearly, and that's a testament to the author's patient, straightforward explanation. I think there should be no highway bridge designer without this book on their shelf, and more widely it should be of interest to anyone concerned with creating simple, effective, visually appropriate bridge designs.
(Footnote: I've reviewed the 1st edition of this book. However, the 2nd edition from 2004 is the one to get, with updated material and far more photographs in colour).