Understanding safety in the work zone
We're in a hurry, we Americans and there isn't much to slow us down. Across the nation, speed limits on state and interstate highways have been increased, if not unofficially abolished. At the same time, we are buying-and the auto industry gladly manufacturing-vehicles designed for speed, not caution. It seems all that slows us down is the rear bumper of the vehicle in front of us. As long as traffic moves fast, so do we.
Occasionally, we speed right past the blinking lights and signs warning us we're entering a roadway construction zone. That's a mistake many Americans make only once. In recent years, an average of 800 Americans have been killed annually in highway work zones, according to the Federal Highway Administration (FHWA). Most of those accidents occur at night and most are due to excessive speeding or inattention by motorists. Along with the unnecessary loss of life, these accidents cost society at least $3 billion every year in hospital care, court cases and insurance coverage.
The legislative fix
"Managing a highway construction zone today is no small matter," said Henry Pearson, Carter & Burgess associate and project manager. "There is little room for error."
In most states, some type of legislative effort is under way to reduce construction-zone accidents. So far, 36 states have enacted laws increasing fines for moving violations in work zones. In Texas, where there were 12,321 injuries and 113 deaths in work zones in 1996, judges can now double traffic fines up to $1,000 for violations in marked work zones. In Georgia, motorists can be fined up to $2,000 and receive jail time of not more than 12 months, depending on the severity of the violation.
One of the most proactive states is Washington, where 60 people were killed and 7,801 injured in work zones between 1991 and 1996. Washington has so thoroughly researched its work-zone accidents that officials know exactly when an accident is most likely to occur. Research shows it is on a Thursday, in August, between 3 p.m. and 4 p.m., with weather either clear or cloudy.
Beginning in 1994, the Washington Legislature began to appropriate funds to attack the problem of work-zone accidents. Highway officials sought, and received, more funds for truck-mounted attenuators, water-filled barriers, changeable message signs and intrusion alarms. Although federal guidelines require zone workers to be visible for 1,000 ft, Washington's Department of Transportation requires workers to be visible for 1,500 to 2,000 ft. During the day, workers are required to wear hard hats and orange vests at all times and at night, they must wear white coveralls under highly reflective orange vests.
Not many states are moving as quickly or as broadly as Washington to improve work zone safety, but they are recognizing the problem and beginning to respond. "The subject of work-zone safety is an evolving issue," said Ben Watts, a Carter & Burgess senior vice president and previous Secretary of Transportation for the State of Florida. "It isn't something that can be solved the same way every time. Every project is different, every state sees the problem differently and motorists' tolerance changes from area to area."
In a significant step in addressing work-zone problems, the American Road & Transportation Builders Association signed an agreement with the FHWA to establish and operate a National Work Zone Safety Information Clearinghouse. The clearinghouse will provide a centralized, comprehensive information resource of work-zone-related statistics, public education and outreach, products, research reports, laws, regulations, training courses and specifications.
Safety and efficiency
What is certain for work-zone engineers is that safety and efficiency go hand in hand. "A work zone that isn't safe isn't efficient," Pearson emphasized. "When you have to reduce the total number of lanes on a multi-lane urban freeway that handles 250,000 vehicles a day, you can't afford to have accidents. Accidents not only imperil lives, but cause costly construction delays."
Liability also is a big reason for contractors to pay special attention to work zones, according to Steve Markovetz, a project manager with Carter & Burgess. "Work-zone traffic control has very high liability. Buildings and bridges rarely fall down, but work zones often have too many variables. You have to take every precaution you can."
The challenge of designing a safe and efficient work zone begins with informing the public that the zone exists, said Pearson, who formerly worked for the Texas Department of Transportation. "That education process should begin with notices in the local media. It should then extend to the work site with plenty of strategically placed signage announcing the work zone ahead and any detours," he said. There is a proper sequence to work-zone signage and it is important to adhere to it explained Markovetz. "In your sequence, you first announce to motorists there is construction ahead, then follow with another sign explaining the type of construction under way. Then you follow by telling motorists what to do about the construction."
Typically, the first advanced warning sign is placed 1,500 ft before a work zone, the second 1,000 ft from construction and the third 500 ft from the work site. On the other side of the work zone should be signs announcing the end of construction work. Signage is particularly critical when detours are required. "Managing traffic in a work zone often includes temporarily redirecting lanes or establishing detours. That means you are changing what motorists have grown accustomed to, so you have to be very careful to get their attention," Pearson said. Detours or lane redirections often add a great deal of expense to the creation of a work zone, which alone may represent up to 20% of the overall cost of the construction project. Before planning a detour, it is important for engineers to drive the area and develop a feel for the environment, Markovetz said. "You must have a sense of the lay of the land," he explained. "You're tying to determine what the road's character will be. For example, will there be any pedestrian traffic?"
The three key considerations in planning a detour are distance, obstacles and the number of turns that will be required. Engineers must also understand that work zones in general-and detours in particular-will have to be regularly maintained. In Colorado, for example, mud and snow must be removed regularly from highway barriers.
Detours must also be maintained to keep the road elevations from becoming dangerously inconsistent. "How you handle traffic through the zones is a primary issue," Pearson said. "It can be very difficult or relatively simple, depending on how much room you have to work with." Because closing lanes often creates dangers and delays, project managers should try to keep the same number of lanes open during construction. In some states, contractors must pay a fee to close a lane on a state highway. Although that isn't common, usually contractors do have to pay to close city streets. "In Florida, the major highways are so heavily used you have to keep at least two lanes open in each direction," said Watts. "It's a matter of safety. You can't take traffic down to 35 mph, you need to keep it up to 55 mph." In Florida, major urban highway construction takes place exclusively at night when there is less traffic.
"To keep open the same number of lanes, you usually have to re-stripe the existing shoulders and use them as travel lanes," Pearson said. A buffer zone is the recoverable area for the driver of a vehicle to return to the travel lane. Usually there is no construction in a buffer zone. "The width of the buffer zone should be maximized. However, due to physical constraints such as limited right-of-way, this is often not feasible."
Studies show, it's between the edge of the road and the point where construction begins that most accidents occur. Consequently, adequate signs and the proper use of channelizing devices are the most important tools in making work zones safe for motorists and workers.
In work zones, where opposing traffic requires physical separation to prevent head-on collisions, the portable concrete traffic barrier (PCTB) may be the appropriate device. "The PCTB has been used effectively in separating two-way traffic," Pearson said. "The barrier usually is 30 ft long and about 2.5 ft thick. Crash tests show the PCTB overcomes the inertia of the vehicle and redirects it back into the travel lane. It doesn't allow a vehicle to cross into another lane and cause a head-on collision." The use of a PCTB is often warranted when an excessive drop-off condition exists. When used for this condition, the PCTB also provides a positive barrier separating the traveling public from construction equipment and workers.
"Where a PCTB is not effective is where there are a lot of driveways and intersections," Pearson explained. Every driveway to any property left open will require a break in the barrier. An unprotected barrier end will negate the safety shape of the PCTB. Proper end treatments are required any time a blunt end is present within 30 ft of the travel lane. These systems can help protect motorists from exposed ends of barriers, fixed objects and other hazards.
The greatest priority is the protection of the traveling public from the construction and the workers from the traffic. The proper use of signs, channelizing devices, marking, lighting and other devices is critical in providing a safe and efficient work zone.
Transportation management devices
In Colorado, where improvements to I-70 are expected to take a year and a half, intelligent transportation systems (ITS) transportation management devices will be used. The ITS application includes variable message signs and surveillance cameras mounted on bridge and overpasses. The cameras monitor what is being displayed on the work-zone message signs so transportation officials can make certain motorists are getting the most updated information.
"Once the project is completed, the cameras and signs will remain and be used to inform police and motorists of traffic accidents ahead," Markovetz said. "The signs will also be used to inform motorists of the locations of arenas and event destinations."
Though no work zone is safe without proper lighting, signage and barriers, that often is not enough given the habits of contemporary American drivers. Highway construction managers across the nation also are seeking a greater presence by law enforcement officials.
"It helps to have a police officer clearly visible," Pearson said. "Even though construction may block the officer from being able to ticket speeders, it is a good deterrent."