Low-cost solutions yield big savings: fatality rates on South Carolina's interstates were rising, but the transportation agency made dramatic improvements that save lives

Public Roads, Nov-Dec, 2003 by Ron Zeitz

South Carolina, faced with a disturbing increase in traffic fatalities, decided to take strong action. But limited resources posed a possible hindrance to meaningful results. The challenge was daunting.

Ready to accept the challenge, the South Carolina Department of Transportation (SCDOT) and the South Carolina Division of the Federal Highway Administration (FHWA) expanded their partnership. "We decided to put our heads together and make safety our number one priority," says FHWA's South Carolina Division Administrator Bob Lee.

Since 1992, the State's fatalities had been rising 4 percent per year. In addition, the State has the Nation's fourth largest State-maintained highway system. In the face of a rising fatality rate and budget constraints, how would South Carolina be able to improve safety?

"Because we couldn't fix everything at once, we took a focused approach," says SCDOT Executive Director Elizabeth Mabry, "and decided to tackle the 1,336 kilometers (830 miles) of interstates as a prime target for fatality reduction."

"Fatalities [on those highways] increased from 89 in 1997 to 162 in 2000," Lee adds, "and because interstates are eligible for Federal aid, we knew we could allocate the funds for some measures that would bring down the fatality rate as quickly as possible."

Slowing Speeds

Mabry and Lee agreed that decreasing speed limits on the interstates where they enter urban areas would be the place to start as a low-cost, high-yield measure. Accordingly, SCDOT reduced urban speed limits in high-crash areas to 89 or 97 kph (55 or 60 mph)--a reduction of 816 kilometers per hour (5-10 miles per hour). SCDOT posted new signs and coordinated with the South Carolina Department of Public Safety and local law enforcement agencies.

"We knew it would be an unpopular decision," says SCDOT Executive Director Mabry, "but our public awareness efforts minimized complaints." The transportation agency also Munched a massive public safety campaign that included nearly 7,000 "Highways or Dieways" broadcast commercials. In addition, the agency established a Web site (www.scdot.org) that ultimately received more than 2,000 hits each month.

The results speak for themselves. Since December 2000, urban interstate fatalities in South Carolina have dropped 54 percent as a result of the project.

Testing Truck Lane Restrictions

Other segments of the Interstate System still seemed to induce crashes, especially those Involving commercial vehicles. In particular, Interstate 85, a major north-south route for heavy trucks, continued to have a number of crashes. National studies showed that lane restrictions potentially could lower the crash rate. When it became known that the State was considering such restrictions, the trucking industry expressed some concerns about safety and operations.

To allay industry concerns, FHWA and SCDOT implemented a pilot project to study lane restrictions. SCDOT established the restrictions temporarily for 1 year on two high-crash interstate segments. The South Carolina Department of Public Safety used targeted enforcement, both for lane violations and aggressive driving violations. The results of the lane restrictions were a 78 percent reduction in truck-related crashes. The outcome enabled FHWA, SCDOT, the SC Department of Public Safety, and the South Carolina Truckers Association to reach a consensus that restricting trucks to the two right travel lanes on three-lane sections would offer improvements in safety and traffic operations. Truck lane restrictions were expanded to 170 kilometers (106 miles) of interstates in the State.

Since the full implementation of truck lane restrictions in 2001, truck crashes on interstates in South Carolina have increased slightly, but fatalities involving heavy trucks have decreased.

Increased lane densities, increased speeds, and unprotected narrow median strips can combine to produce a far higher potential for head-on crashes.

The Message Is in The Median

Narrow, unprotected median sections were under the scrutiny of the two partner agencies. Median crossover crashes on interstates in South Carolina warranted special attention because of the devastating effects and multiple loss of lives almost always associated with this kind of incident. In 1999-2000, more than 70 people in South Carolina lost their lives in 57 separate interstate median crashes. Causes for median crossovers include inattention, fatigue, improper lane changes, medical emergencies, and equipment failure, among others.

Were these median crossover crashes occurring at a particular location or set of locations? To find the answer would require the analysis of some 3-5 years' worth of crash reports, numbering between 24,000 and 40,000. A cursory review of some of the fatality data indicated that these incidents were random in nature and did not appear to be isolated to specific locations.

A series of three median crossover crashes that killed 13 people in a 3-month period on one 16-kilometer (10-mile) stretch of highway raised doubts about this theory. The three incidents suggested that the narrower the median strip and the higher the traffic volumes, the greater the chances for a head-on collision. In addition, the length of the on- and off-ramps in this section, short by today's standards, appeared to contribute to frequent vehicle weaving conflicts. SCDOT and FHWA established priorities for correcting these dangerous situations, and determined top candidates for installation of barrier systems based on median widths of 11 meters (36 feet) or less. All traffic barrier systems used on the National Highway System must conform to the National Cooperative Highway Research Program (NCHRP) standard for crash barriers--NCHRP-350 criteria (NCHRP's Recommended Procedures for the Safety Performance Evaluation of Highway Features, NR-350). Although five types of crashworthy barrier systems are available (see "Barrier Systems Compliant with NCHRP-350 Criteria"), each has its advantages and disadvantages, and some would not be entirely satisfactory for South Carolina interstates.