or property boundaries on other layers, as well as the raster image beneath.

Drescher said the feature provided enormous design flexibility. "Having that background image while designing lets me see that if I move this line here, it's going to go through these houses or across that wetland, so I'll try shifting it this way because there's a vacant lot on the other side of the road -- different scenarios like that. We had many areas with sensitive wetlands that we deviated the alignment from to avoid impacting. The software gave us the flexibility to experiment with curves, try different ideas, and immediately see what the impact would be."

Brady believes a small shop could get into this as easily as a large firm. "There's nothing cost prohibitive about the process; it can all be done on a stand-alone PC. We just exploited some GIS applications to come up with an easier, faster process of producing quality file products."

For the SR 60 PD&E study, about 40 positives of aerial photographs were raster-scanned into TIF files (a common raster image format). G&O used Descartes to convert the files into a single image of the entire 25-mile route. "It's a very quick process," Brady said. "As soon as we have it in a format Descartes can use, we put it in the same file as our topographic baseline survey and match up the coordinates. When everything lines up, the topographic file lies right on top of the background image."

"The way we set up our files," Drescher explained, "makes it relatively easy for a number of people to work on the same project simultaneously. Design changes by the engineer are reflected over to the CAD technician, who may be working on annotations or color coding. At the same time, the survey and environmental departments can be looking at the same files to see if there are changes the project manager may need to make. The process really facilitates communication."

"Users of the design file can always get updates," Brady added. "With Microstation, you just press a reload button, the screen flashes, and a few seconds later the image is back up with the latest changes."

When the design phase of an alignment segment is completed, the CAD technician adds the data from associated files -- baselines, utilities, annotations, attributes, etc. When all three alignment alternates are complete, the entire route is divided into four segments, and each one is analyzed for the best alignment characteristics. These are linked together to create a 25-mile, preferred alignment for the route.

PUBLIC HEARINGS

Final plans of the PD&E study are produced in digital format and in color, on 11 X 17 sheets, from a Hewlett-Packard 650 plotter. At a scale of 1 inch=100 feet., there are about 300 drawings. For public hearings, however, the proposed alignment for the 25-mile route will be plotted out on four, 11-inch X 100-foot rolls (one for each alternate) and displayed on walls or laid out parallel on tables. Brady said that a similar display for public hearings on the Miami Garden Drive project was "very successful; people could easily see how the alignment would impact their properties. The DOT project manager for Miami Garden Drive said it was the smoothest public hearing they'd ever been through."

ASSESSMENT

Yue pointed out that although

the public hearing is scheduled for May 1996, public information meetings have been held already. "Since the public could visualize all the alternatives clearly, the project was favorably received. Electronic images of the aerial photographs show very accurately the impacts associated with the improvements. The ability

of G&O to produce exhibits of the images in various sizes has made it easier

to communicate with the public.

"CAD and raster technology," Yue added "make it possible for the