Posted December 17, 2004 Atlanta
Study Documents Hazards & Solutions
Rural two-lane highways are the largest single class of roads in the United States -- and they are the deadliest, especially in the Southeast.
From 1996 to 2000, almost one-third of the nation's traffic fatalities occurred in just eight southeastern states, and of those, 64 percent occurred on rural roads, according to a recent Georgia Institute of Technology study. Take Florida - a less rural state - out of the analysis, and 71 percent of traffic fatalities in the region occurred on these highways as compared to 59 percent nationally.
"The most frequent crashes in the Southeast occurred on rural roads in wooded areas where people ran off the road and hit a tree," said Georgia Tech Associate Professor of Civil Engineering Karen Dixon, who headed the regional study funded by the Federal Highway Administration (FHWA) via the Georgia Department of Transportation (GDOT).
With reports from southeastern transportation officials and researchers, the study quantified the top highway safety concerns - including rural roads - in Georgia, South Carolina, Alabama, Mississippi, North Carolina, Kentucky and Florida. Tennessee chose not to contribute a report. The study also recommended countermeasures, such as lane and shoulder widening.
On rural roads, the most common contributing factor to traffic fatalities was late-night driving by tired or apparently intoxicated motorists, especially on weekends, Dixon noted. Many of these victims were males between ages 16 and 25.
The study also found that 48.6 percent of the region's fatal crashes involved drivers who did not wear seatbelts, she added. In a related finding in Georgia's report, Dixon discovered a disproportionate number of pickup trucks involved in fatal crashes.
"This is partly because pickup trucks are more often driven on rural roads and because, in Georgia . pickup drivers cannot be stopped by police solely because they're not wearing their seatbelt," Dixon said. "I think this study shows we need to take a second look as this law and reconsider it."
Another of the study's findings lays potential blame for fatal crashes on the 2.5- to 5-inch pavement drop-offs often found on rural highway edges.
"Almost half of the non-state maintained roadway crashes we looked at had an edge drop-off issue," she noted. "We don't know if this caused all of these crashes, but nonetheless, the potential exists for it to be a serious problem."
Drop-offs develop as roads are repaved and/or soil erodes along the shoulder. And roadside ruts are caused by rural mail carriers who drive with one side of their vehicles on the road and the other on the unpaved shoulder, she added.
To address the drop-off concern, some state and federal transportation agencies are considering changes in roadside edge treatments (e.g., planting grass) and trimming of tree branches along the roads. And a GDOT pilot study is under way to test the durability of a new tapered paved-edge treatment. GDOT plans to specify the new tapered paved-edge treatment on a project-specific, rather than general, basis beginning in January 2005.
Other fatal crash contributing factors cited in the study are: collisions with commercial trucks (one of every eight traffic fatalities), speeding, inexperienced drivers, weather and driver reaction to an unexpected occurrence in the car or on the roadway (e.g., a deer in the road).
Countermeasures recommended in the study include: widening of lanes and shoulders, road alignment improvements, and the addition of advisory speed signs or other speed controls.
A proposed follow-up study would use the southeastern state traffic fatality databases to do cross-sectional comparisons of contributing factors.
In other transportation safety-related studies headed by Dixon:
The GDOT funded development of a new computer tool for evaluating the state's rural transportation improvements - including those prompted by safety concerns. Called the Multimodal Transportation Planning Tool (MTPT), the program addresses aviation, commuter rail, intercity bus systems, transit for disabled citizens, highways and bicycling. It also contains an environmental justice module to address the impact of transportation improvements upon minority populations.
"The program looks at the various potential modes of transportation and the infrastructure associated with them and then evaluates them for suitability for and compatibility with the area," Dixon explained. "For example, if the tool shows that an area is not suitable for bicycles, it would show what improvements would be needed now or 10 or 20 years in the future and the cost of these."
The tool allows users to select an evaluation region based on GDOT district, Regional Development Center (RDC), county, highlighted selection from a map or by road corridor. Results are displayed in a text report and in a geographic information system (GIS) map for the highway, bicycle and environmental justice modules.
Dixon is particularly excited about the MTPT rural environmental justice module. It addresses how transportation plans may affect air quality and noise pollution, for example, for a minority population in any RDC area. "If transportation improvements are planned, the tool will determine whether the plans are sensitive to the minority population so officials can avoid poor decisions," she added.
Dixon expects that both GDOT and the Georgia Department of Community Affairs, which oversees some municipal transportation projects, will use MTPT.
Also for GDOT, Georgia Tech researchers are evaluating several technologies designed to protect drivers and road workers from incidents in work zones.
"We have a serious problem in the United States with speeding in work zones," Dixon said. According to the National Highway Traffic Safety Administration, 2,705 people were killed nationwide in highway work zones in 2001.
The systems designed to prevent such accidents collect information on driver speed with microwave sensors or radar technology. And they use changeable message signs to alert drivers of a forthcoming work zone, caution them to slow down and post an estimated travel speed or delay time.
User surveys revealed that the driving public appreciates the advance messages, but only half believe the time estimates are accurate, she noted. Nonetheless, the changeable message sign with radar technology has proven effective in reducing work zone speed, Dixon added.
Dixon and her colleagues are testing three technologies on interstate highways in Georgia, and the other one - a smaller, simpler system - is being studied on a rural highway with a lot of commercial truck traffic. The latter system posts a caution message to individual drivers who are speeding.
"It's important to know which technologies are good for which scenarios," Dixon explained. "Some are better for short-term road work only, and some are better for long-term work . We also want to know the optimal placement for these systems."
Dixon expects to report the final study results to GDOT by the end of this month. "The Federal Highway Administration is watching for the results of this study, as are some other states," she added. "These technologies are expensive, so they want to make sure the investment is worth it."
Another study recently begun by Dixon and Georgia Tech Professor of Civil Engineering Michael Meyer focuses on the effects of context-sensitive roadside treatments (e.g., trees, signs, sculptures) on highway safety for drivers, pedestrians and bicyclists.
"For example, some people think trees should be removed along urban roads to prevent people from crashing into them, but others say the trees create a pleasing environment that makes drivers slow down to enjoy it," Dixon said. "We don't know the answer yet, but we want to see if context-sensitive roadside treatments have an effect on the transportation system. Then officials can make a better decision on when to make the tradeoffs that may be needed."
One question researchers are asking is what size trees are safe along the roadside, she noted. An old study using wooden poles in a concrete base suggests trees of less than four inches in diameter are OK because they will bend, rather than break, if hit by a vehicle. But this study may not provide an appropriate comparison to four-inch diameter trees with established root systems, Dixon explained. Another question relates to the impact of curvy versus straight roads on speed.
The researchers expect to complete this study by December 2005. The study is being funded by the National Research Council.
RESEARCH NEWS & PUBLICATIONS OFFICE
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 100
Atlanta, Georgia 30308 USA
MEDIA RELATIONS CONTACTS: Georgia Tech: Jane Sanders (404-894-2214); E-mail: firstname.lastname@example.org); Fax (404-894-4545) or John Toon (404-894-6986); E-mail: (email@example.com) or Georgia Department of Transportation: Karlene Barron (404-463-6460); E-mail: (firstname.lastname@example.org)
WRITER: Jane Sanders