Some few brave bridge designers fought against this. Switzerland's Jorg Schlaich, for instance - famous for highly sculptural road bridges - found that, when it came to designing a humble motorway overbridge at Kirchheim, the expressive structure he suggested, made of tensioned cables and struts, was frowned upon: such designs, it was felt, would invite vandalism and sabotage. So Schlaich therefore found himself obliged to encase his 1993 structure in concrete, while maintaining the profile he had originally wanted.

Architects do design read-at-speed bridges, but their talent for detailing has so far been more exploited on pedestrian examples, particularly in urban regeneration projects. There is a colossal difference between the macro-detailing of, say, the Great Belt Bridge in Denmark - which is all about a speed-journey - and the micro-detailing of some of the present crop of pedestrian bridges which are not so much to do with journeying as with promenading. Texture and feel of surfaces, scale of components, sense of movement underfoot, a feeling of shelter and security, even sound and light reflections, become important. A timber deck may feel warmer and more human, but can become slippery in the wet: how to keep that human feel when using man-made materials? A consistent curve of the deck, rising to and falling from the point of maximum clearance, looks best - but how to square this with a requirement to provide flat refuge-points for those in wheelchairs? The all-important handrail - could this be made unique or at any rate special, for instance with a coating derived from industrial diamonds as one competition-winning British bridge design proposed?

Such details are very much the preserve of architects rather than highway engineers: human interface is what they grapple with in their work constantly. Thus Norman Foster could have a more significant design input into the Millennium footbridge across the Thames in London from the Tate Modern museum of modern art to St. Paul's Steps on the north bank than he could at the Millau viaduct. In London, he required of his engineers, Ove Arup, a structure so slender as to resemble "a blade of light". This led to a design that is a highly tensioned suspension structure without towers, the footway sitting directly upon the cables rather than hanging from them. The design is inspired by the spidery rope-bridges of central Asia. Like them, it was inclined at first to swing from side to side, rather more than had been anticipated. Remedial damping work was needed, but the all-important image was carefully maintained - the bridge had become a popular attraction even when closed. In that case, then, an architect created a seemingly reduced, minimalist structure which might at first glance be mistaken for an act of "pure" engineering - but this was not the case. Architects and engineers worked together in the service of an aesthetic ideal, and while the aesthetic reference was ancient, the means of achieving it was extremely modern: so modern as to require entirely fresh thinking.

Frequently such historical references crop up in architecture, less often in bridge design, though there are contenders. One such is the 1673 Kintai-Kyo bridge in Iwakuni, Japan, which looks startlingly contemporary, being so reduced to essentials. Timber arches between rubble stone piers form an undulating walkway of stairs and smooth crowns: the arches are the walkway, there being no horizontal deck placed above them. The entire timber structure of this bridge used to be renewed every 25 years, by rebuilding one of the five arches every five years. This stopped when modern timber preservatives meant that the quinquennial renewal process could halt -or at least be considerably slowed - following a complete rebuild in 1953. Hence, to some extent, its modern feel. Crossing this bridge may be hard work, but its ceremonial power is immense. Why, after all, should a bridge not undulate, assuming provision is made for the less able-bodied?