Over the past three decades, the face of public works has undergone tremendous change. The building booms of the '50s and '60s have given way to maintenance mania, as the streets, highways and buildings constructed during America's post-war years begin their inevitable decline.

Additionally, the individuals occupying the country's public works offices have evolved, morphing from straight engineers into administrators and managers just as concerned with building bridges in the figurative sense as they are with building bridges in the literal sense.

Changes in the tools of the trade have been the key to this evolution. Slide rules, once considered indispensable items in the public works arsenal, have fallen before an infestation of computer mice. Hardware is now more likely to mean keyboards than hammers.

All this has translated into more efficient, user-friendly infrastructure. >From pavement management systems to GIS to computer-aided design, technology is changing the way public works works. This month, American City & County looks at five of those technologies and their implications for the future of the business.

Computer-Aided Design

Building bridges - or intersections or treehouses, for that matter - has always been easier than building consensus. And for years, public works directors contented themselves with doing the former well. The latter they generally left to the administrative types - mayors, city managers, budget directors, county commissioners.

Three letters changed all that. CAD, computer-aided design, has given the designers and builders of the nation's infrastructure a window into the hearts and minds of the citizens who will ultimately use the results of their efforts.

CAD has been around for nearly two decades. But it wasn't until the early to mid-'80s that it made the leap from the nation's engineering offices to the offices of city planners. And itwasn't until after the Los Angeles riot s that followed the Rodney King verdict that its progeny, Urban Simulation, began to make its way into the design lexicon.

Bill Jepson was the catalyst. Jepson, director of computing at UCLA's School of Architecture and Urban Planning, had been approached by Rebuild L.A. to do a video survey of the city's Pico Union area, nearly destroyed in the riots. Using tools already available, Jepson built a three-dimensional map of the area. Then he figured he could create a virtual environment that would show city officials what it could look like, given a little planning and a lot of vision.

Urban Simulation was born; its parents were three-dimensional CAD and Military Flight Simulation Training Technology (FST). CAD allowed engineers to create 3D models using the geometry of an area. FST added the texture mapping that gives viewers the ability to see the area from their own unique perspectives.

That ability is now changing the way builders build.

Seeing is believing

The Bay Bridge in Oakland, Calif., damaged during the Loma Prieta earthquake of 1989, was due for replacement. The state, for financial reasons, had opted for a viaduct version, and Gov. Pete Wilson had made it clear that he would not agree to fund anything else.

At the same time, a group from Coryphaeus Software, a Los Gatos, Calif., provider of real-time 3D software, and Silicon Graphics, a Mountain View, Calif., supplier of interactive computing systems, was conducting an American tour extolling the virtues of Urban Simulation. It was at the tour's first stop, San Francisco, that the group was approached by a representative of CalTrans' District 4, the DOT district responsible for the Bay Bridge replacement program. Could you do this for a bridge? he asked. "We've got three aerial photos that have been touched up in Photoshop," he said. "But the Oakland people keep asking, 'What does it look like from the Oakland side?' We can't show them."

Coryphaeus and Silicon Graphics jumped at the chance. Donating time and equipment, the partnership pulled terrain data of San Francisco off the U.S. Geological Survey's web site and satellite images of the area off another site. With drawings from CalTrans and a camera that takes 360-degree photographs, it went to work. "Everybody was leaning toward the viaduct," says Matt Cuerdon, AEC marketing manager for Silicon Graphics. "Without any visual information, you base your decision on pure economics."

Using CAD and FST, the partnership came up with 12 bridge variations, ultimately whittled down to a single-tower, cable-stayed; a suspension; and, for good measure, Gov. Wilson's viaduct versions. The results were shown in SG's Visionarium, an OmniMax type theater that features a huge, curving screen. The simulation changed minds. Northern Californians, proud of their beautiful hills and the world-renowned Golden Gate, realized that, with the cable-stayed and suspension versions, the towers rose majestically above the hills, more in keeping with the Golden Gate and the western span of the Bay Bridge. The viaduct blended.

A series of town meetings confirmed the choices. Californians were even willing to pay higher tolls to help finance the bridge. Currently, CalTrans is getting cost estimates before another series of town meetings determines the winner.

"The most difficult thing to obtain on any project is consensus," Cuerdon says. "Typically, the non-engineer, non-architect doesn't understand drawings and can't picture verbal descriptions. This technology allows the non-expert to see what it looks like from all angles. We showed them what the bridge would look like if they were flying in a helicopter, driving over it, sailing under it. We showed them the bridge from Oakland, from San Francisco, from the Yerba Buena Hills.

"Urban simulation allows us to bring all these people together, all the stakeholders - the architects, clients, local population, local and state political bodies, city and county building departments, fire departments, financial backers and the various interest groups - and walk them through multiple proposals. We can show them what it looks like at High Noon in Summer and in the morning in November."

Still, the addition of FST was merely the icing on the cake. In Bellingham, Wash., it wasn't even necessary to turn a pool project around.

The project, an indoor community pool, was feared dead when voters rejected a bond issue that would have funded it. But a citizens' group, unhappy with the vote, approached City Hall with a proposal. It would raise the money itself to show citizens what the project would look like. A design committee, made up of a local architect, the local high school swim coach, the parks director, a semi-professional swimmer, a local road building contractor, a doctor and a civil engineer, did just that. The project was modeled in 3D using Softdesk's AutoArchitect and the resulting images sent out to the community. The citizens were sold.

The local architect, Zervas Group, which had spearheaded the design, was chosen for the final design, partly because it created a full-motion video of the proposed facility.

The video, aired on local television programs and distributed throughout the community, allowed decision-makers to actually "fly through" the building.

Single-project designs are one thing; the fascinating thing about the emergence of computer design as a community relations tool is its incredible breadth. Designers can create bridges, pools, intersections and vast stretches of highway, but they can also create entire cities.

ModelCity Philadelphia is such a creation. Created by Exton, Pa.-based Bentley Systems and Mike Rosen and Associates, a local architect, ModelCity Philadelphia uses 3D imagery in a model designed with future city planning in mind.

When the model is completed in three years, it will contain every building, utility line, transportation route and water line that a planner would need to know about in order to get a project off the ground. More importantly, it can be accessed by citizens and visitors via the Internet, and thus serves as a powerful community relations tool. "It provides so many great opportunities for city planning," notes Philadelphia Mayor Ed Rendell.

"It's the type of technology that will help us design and build better cities,"says Terry McDermott, chief executive officer of the American Institute of Architects.

That, of course, is what public works is supposed to do.