WILMINGTON, Del. — Spotlights with four 1,000-watt bulbs illuminate the night, the harsh artificial light casting odd shadows that distort the look of the tractors, drills and other construction equipment lined up on the side of the noisy highway.

Just outside the circle of light, darkness again takes over, broken only by the steady stream of cars' headlights and the occasional flash of a road worker's lime-green reflective safety vest.

Some of the drivers shout obscenities at the workers, or even aim their cars at them. But most just speed past, slowing only slightly at the sight of the neon-orange barrels and cones.

It's a no-brainer, construction workers say, that night projects are harder. But on a busy highway like I-95, where the traffic never ceases, night construction is the only way to go, they say.

"People just don't want us to affect their daily commute," said Javier Torrijos, a Delaware Department of Transportation engineer. "If we took one lane of I-95 during the day, it would cause major congestion and backup. There's just too many people that travel during the daytime."

SAFETY CONCERNS

More states are turning to night construction to minimize traffic snarls and delays during rush hours. But the increase in night work also means an increase in safety concerns both for motorists and workers, leading federal and state officials to call for studies of the safety of nighttime work zones. Each year, about 40,000 people are injured in more than 100,000 crashes in work zones.

"It's a more extensive operation than during the daytime," said Bill Stewart, area engineer in DelDOT's paving and rehabilitation program. "You're always a split second away from something catastrophic happening."

With more construction being done at night, safety concerns for an already-dangerous situation are heightened, but as of yet, data about whether night construction is more dangerous than day construction is hard to come by.

In 2005, there were 1,074 fatalities in work zones, about half of which occurred during the day, according to the Federal Highway Administration. That's up from 989 in 2001. Drivers and passengers account for an estimated 85 percent of those deaths.

The Texas Transportation Institute at Texas A&M University has conducted a study for the Federal Highway Administration, to be submitted to Congress later this summer, that looks at safety of night work zones, and the impact on businesses and residents.

The institute also is finalizing a report for the National Cooperative Highway Research Program to compare the safety of daytime and nighttime work zones, said Gerald Ullman, Texas Transportation Institute senior research engineer.

Some believe working at night is less dangerous because the lower traffic counts mean fewer traffic tie-ups and less of a chance for rear-end accidents, Ullman said.

A second school of thought, however, believes night construction is more risky because of a higher percentage of impaired drivers, whether because of alcohol or sleepiness or because they just can't see as well in the dark, he said.

Less traffic at night also means traffic travels faster, which poses more of a threat to workers, Ullman said.

APPROPRIATE PROJECTS

The two reports, he said, will help decision-makers determine which projects are most appropriate for night work, and help them make sure drivers and workers are as safe as possible.

Vince Ruff, project manager for the I-95 widening, recalled a time when he was working on a construction site at night and a car aimed at him, swerving away at the last second. Ruff wasn't hurt, but said the driver was "messing with him."

"Working in the dark, people don't see you very well, so you have to remind yourself you're in a pretty awkward spot," he said. "We have to be mindful because anything can happen."

With the country's aging highway infrastructure, and the inability to build new roads to keep pace with increased traffic, it's no surprise that night work has become the trend, Ullman said.

But moving to nighttime construction to avoid congestion is not necessarily a trade-off for motorist and worker safety, he said.

"If you take precautions, you can work at night," he said. "And that does have a significant advantage from the public's standpoint."