ONE OFT-CITED EX ample of technology imposing social control involves the seemingly prosaic subject of highway overpasses on Long Island. As Langdon Winner pointed out in a famous 1986 study, during the 1950s Robert Moses, New York State’s planning czar, deliberately built them too low for buses to fit underneath. This decision, while cloaked in the language of engineering necessity, reflected Moses’s hope that poorer residents who did not own cars would be unable to visit Jones Beach, which he envisioned as a middle-class resort.

The story shows how building a bridge can be as much a political exercise as an engineering project. Examples of the give-and-take involved can be found by considering the disappearing drawbridges of Pinellas County, Florida.

Since boating is so important in the Sunshine State, coastal water crossings must accommodate both those passing over and those passing under. One timehonored solution is a drawbridge, which can be opened to let boats pass. Florida’s more than 1,000 miles of coastline contain about 150 drawbridges, more than are found in any other state. As these bridges age and Florida grows and changes, many of them now have to be replaced. But replaced with what?

With shores on both Tampa Bay and the Gulf of Mexico along with a chain of barrier islands and assorted bays and inlets, Pinellas County has seen many recent controversies over drawbridges. One involved the Belleair Beach Causeway, which was built in 1950 across the Intracoastal Waterway. When it approached the end of its 50-year lifespan, the choice for a replacement came down to three options: a drawbridge the same height as the existing span (21 feet above high tide) but wider, to accommodate modern traffic levels; a drawbridge with a height of 45 feet; and a fixed span 65 feet tall. Each choice had its advantages and disadvantages.

The low bridge would have created the least disruption in nearby communities. Opening a drawbridge inconveniences motorists, however, and can cause a dangerous delay for ambulances or in other emergencies. A drawbridge also costs more to build and maintain. A high fixed span would be cheaper and eliminate the delays, but it would require extensive property acquisition to accommodate its approaches. It would also tower over the area and block the views of many residents, and some tall boats would be unable to fit underneath. The compromise plan of a higher drawbridge would have combined the advantages and disadvantages of both options. After much debate and many hearings, the county board settled last year on a high fixed span.

As in Winner’s example, choosing a bridge design can have race and class dimensions. One Floridian has decried the arrogance of the state’s wealthy, who “think nothing of holding up hundreds of working people at the drawbridges while their swank luxury yachts sweep through on pleasure cruises.” Yet in the dispute over replacing the Pinellas Bayway, near St. Pete Beach, yachtsmen opposing a fixed span found an unlikely ally in the NAACP, which pointed out that many local residents, often poor and black, feed themselves by fishing off the existing low drawbridge. Here again, despite the objections, a fixed span was ultimately chosen.

A high fixed bridge is usually quieter than a drawbridge, but at John’s Pass, which connects two barrierisland communities, a resident told the St. Petersburg Times that he had moved to the area for “the fishing village element—I like the bridge opening and closing at night and the sound of the bells and the horns.” Since a fixed bridge at John’s Pass would have required a rise in the middle, opponents also feared that it would create a “thrill hill” that youngsters would drive across at high speeds late at night. And local merchants worried that a fixed bridge would discourage motorists from stopping at their stores.

The choice of a bridge design was particularly important at John’s Pass because its drawbridge is the only one in the county that opens on demand, rather than on a fixed schedule. Currents at the inlet are particularly fierce, and making boaters wait would be too dangerous. (The existing span dates back only to 1971, but the currents have already caused extensive damage; some pilings that originally sat on the inlet’s floor had to be shored up after they were found to be dangling.) This unpredictability makes life even tougher for motorists. Yet a fixed bridge would make a stretch of the Intracoastal Waterway impassable to boats taller than 65 feet, so that option was ruled out. When an examination of tenders’ logs showed that increasing the height would reduce the frequency of closings only slightly, the state decided to build a new drawbridge with the same height as the old one.

Elsewhere, enlarged bridges have been built with special attention to aesthetics to make up for their increased size. On the Treasure Island Causeway, commissioners chose to build a new, higher drawbridge in the visually appealing “Florida vernacular style” rather than the less expensive bare-bones option. In Clearwater the Memorial Causeway, due to open this spring, replaces a 1963 drawbridge with a handsome and expensive 74-foot-high fixed span. Even before it was built, the new bridge was named one of seven “Landmark American Bridges of the 21st Century” by the Boston Society of Architects. With 360 feet between piers, it affords a wide-open view of the harbor, which it snakes across in an S curve, while details such as coral pink paint and pedestrian outlooks give it a distinctly Floridian feel.

All these projects show how civil engineering has changed since the days of Robert Moses. The list of groups to be met with, impact statements to be filed, laws to be complied with, and concerns to be addressed grows ever longer. Yet the result, if done properly, is well worth the trouble: technology chosen openly, democratically, and consensually, rather than being imposed from above.