By the time Bryan Lee headed to work along Highway 51 in Texas on Sept. 15, 2005, the road-building industry and its government overseers were aware of a deadly, though easily corrected, construction hazard: pavement-edge drop-offs.

Accidents involving dangerous drop-offs kill about 160 people and injure 11,000 each year. Numerous studies have shown that the deeper the drop-off, the greater the danger.

Yet when the contractors repaving Highway 51 west of Fort Worth discovered they lacked sufficient equipment, they decided to pave only part of the roadway and finish the rest days later, leaving a sharp drop-off that ran for miles within the travel lane. A state inspector warned that it was dangerous, but no one—not his superiors, not the contractor—listened.

Two days after that warning, Lee, a 26-year-old oil-field worker with a wife and two sons, rounded a curve and the wheels of his motorcycle slid off the asphalt edge. He tumbled from the bike and was run over by a pickup truck.

The deadly accident was one of thousands in highway work zones across the country that have killed at least 4,700 people—more than two a day—and injured 200,000 in the last five years alone.

Behind this human toll is a litany of hazards: concrete barriers in the wrong position, outdated lane markings, warning signs never deployed. Yet there are virtually no regulations mandating safety measures in work zones. Standards differ from state to state. As a result, there are few penalties levied against contractors when, because of ignorance, carelessness or a desire to save money, guidelines are violated. Problem contractors often just keep on getting hired, and dangerous practices remain uncorrected, sometimes for years.

Ultimately, the hazards persist through a kind of collective indifference, a presumption that accidents happen.

But interviews and government documents, along with a review of more than 100 legal cases involving work zone crashes around the country, illuminate a more complex calculus of blame.

“;A lot of work-zone crashes are entirely preventable,”; said David Holstein, Ohio's chief traffic engineer. “;It's not explainable by just driver error or inattention. We can intervene to keep them from happening.”;

After transportation officials in Ohio created a system to monitor work-zone crashes in real time, they were startled to discover that the presence of construction caused accident rates to jump as much as 70 percent, Holstein said.

“;We were seeing that crashes were happening day after day after day, and nothing was being done about it,”; he said. “;Sometimes there were hundreds of crashes over the life of a project.”;

Now the stakes are increasing, as $27 billion from President Barack Obama's economic stimulus package is prompting a nationwide boom in highway construction. Federal transportation officials are concerned that work-zone fatalities, after declining in recent years along with traffic deaths in general, could rise again.

Transportation officials are responding pretty much as they always have: By focusing primarily on drivers. Jesse Sepeda knows the system well. He is a safety director for a major highway contractor in Texas. He also lost his 18-year-old son, Anthony, in a work-zone crash last year.

There were no warning signs or barricades, but a utility contractor digging a trench had parked a backhoe less than two feet from the travel lane on Wells Branch Parkway in Pflugerville, where the speed limit is 50 mph. Construction industry standards say unused equipment should be at least 30 feet from the roadway.

Anthony's motorcycle drifted too close and hit the backhoe. After the accident, the backhoe was moved and barricades went up. But the police found fault only with the victim, concluding he had probably been going too fast.

“;I'm in this business, and I can tell you that these things happen all the time and there is nothing to hold a contractor accountable,”; his father said. “;In most cases you can't do anything except go to court, and meanwhile the contractor just goes on doing his work and killing people.”;