The designers of I· 70 tl· 1rough Glenwood Canyon, Colorado, were responsible to reviewers from many backgrounds. All wanted to find a good fit between highway and natural landscape, but their definitions of" good fit" varied. Ac· curate graphic descriptions of the canyon and of alternative highway proposals were important to designers and reviewers. These were needed to show con· ventional highway plans, profiles, and sections; to show the appearance of the highway in the natural landscape; and to show the precise relation between highway alternatives and landforms and plant communities taken or impinged upon. Canyon and highway alternatives were described by using conventional artist's sketches, colored slides and black-and-white photographs, surveyed cross sections combined with perspective backgrounds, environmental maps, isometric drawings, composite drawings or" story boards", computer graphic cross sections at close intervals, highway representations painted into photo· graphs, scale models, full-size mock-ups, and even diagrams and cartoons. An isometric projection technique developed for the project was particularly help· ful in the design of the highway in the western half of the canyon. Both land· scape and highway alternatives can be drawn in isometric with engineering ac· curacy and combined, with much of the realism of an architectural perspective. Highway designers and reviewers have traditionally come from similar back· grounds and have communicated through familiar methods. The Glenwood Canyon work was typical of recent projects in which unusual proposals were reviewed in a process more like a New England town meeting. In such a setting, the ability to communicate lucidly, in words and images, is an important aspect of highway engineering.

In the design of I-70 through Glenwood Canyon, Colorado, alternative proposals were examined in a series of iterations, each of which lasted about a month. The work was reviewed frequently by the district engineer and the project engineer for the Colorado Division of Highways (CDH), by representatives of other agencies and a Technical Review Group, and, finally, by representatives of all of these groups and the seven members of the Citizens Advisory Committee for Glenwood Canyon. The design of a highway in mountain terrain is the problem of fitting a ribbon of concrete and asphalt, shaped by its own precise geometric rules, to a natural landscape shaped by the very different rules of geology. Whereas each of the reviewers was searching for a good fit between highway and landscape, their definitions of" good fit" varil;! d dramatically and sometimes conflicted. The participants in this process brought many points of view to the work, and the designers were asked to investigate a large number of unusual alternatives. The presentation of these alternatives had to meet the following requirements: