FHWA Ruling on NCHRP-350 May Change Face of Work Zones

Dec. 28, 2000
Four years ago, the National Cooperative Highway Research Program published Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. Based on this report, the Federal Highway Administration (FHWA) established a Final Rule requiring all new National Highway System projects use devices meeting the NCHRP-350 requirements for crashworthiness. For the first time, FHWA is proposing that work-zone traffic-control devices must be accepted as crashworthy.

The ruling is expected to go into effect Oct. 1, 1998. Currently acceptable temporary concrete barrier designs may continue in use until Oct. 1, 2002, before they are subject to the Report 350 criteria.

"In 1991, Congress directed us to adopt performance evaluation standards that accommodate vans, mini-vans, pickup trucks, and four-wheel drive vehicles," said Nick Artimovich, FHWA highway engineer. "The FHWA adopted Report 350 because it incorporated the latest in crash-test guidance, as well as answered the charge from Congress to test with vehicles in the 'small truck' category. We are now proposing implementation of the guidance, and work-zone devices are part of it."

Although the ruling has been on the books since 1993, little action has been taken by manufacturers to prepare for the pending change. With the compliance deadline looming, questions about what the ruling really means have started popping up.

"One of the first questions we had was who will be responsible for obtaining a device's acceptance," said Henry Ross, chair of the American Traffic Safety Services Association NCHRP-350 Task Force. Ross is vice president of sales and marketing at WLI Industries, Villa Park, Ill., a company that makes barricades, signs, and warning lights. "If you use a plastic drum from one manufacturer and attach a warning light from another, who is responsible for getting the complete device tested? The drum manufacturer, the light manufacturer, or the traffic-control company? It can get very complicated."

Ruling creates wide spread effects

The ramifications of this ruling are far reaching. State and local transportation departments would have to ensure their NHS projects comply with the new ruling or risk losing federal funds for a given project.

Road contractors would need to use devices that comply with the ruling or risk losing the project. Traffic-control companies would need proof their devices are FHWA-accepted to win projects. And traffic-control device manufacturers will need to show that their devices are crashworthy to obtain sales.

Prior to Report 350, NCHRP had published a 1980 report (Report 230), Recommended Procedures for the Safety Performance Evaluation of Highway Safety Appurtenances. For 12 years, Report 230 served as primary reference for full-scale crash testing of highway safety appurtenances in the U.S. and many other parts of the world.

One of the most significant changes in Report 350 is the expansion of test procedures. A wider range of highway safety features, including work-zone traffic-control devices and truck-mounted attenuators, are included.

In addition to expanding the scope of crash testing, NCHRP Report 350 offers several other updates:

-- Metrics (SI units) replace customary U.S. units of measurement. Hard conversions were used, altering the mass, speeds, and testing tolerances. For example, tests previously specified for 60 mph (97 km/h) are now specified at 100 km/h.

-- The basic test vehicles are an 820 kg automobile and a 3/4-ton pickup truck to reflect the fact that approximately 25% of all passenger vehicles on U.S. roads are in the "light truck" category, and the percentage is growing.

-- Single-unit cargo trucks (8,000 kg), and tractor-trailer vehicles (36,000 kg) are included for testing to meet higher performance levels.

-- Six test levels for various classes of roadside safety features are established, with a variety of optional tests to provide the basis for safety evaluations to support more or less stringent performance criteria.

-- Guidelines for selecting a critical impact point for crash tests on redirecting-type safety hardware have been added.

-- Information on enhanced occupant risk measurement techniques is included, with guidelines for device installation and test instrumentation.

-- Levels for two of the three basic evaluation criteria categories were altered to reflect recent research findings.

-- State-of-the-art testing methods and technologies, such as surrogate test vehicles and computer simulations, are incorporated into the procedures, and

-- Optional side impact testing is included.

Four acceptance categories developed

To assist companies in meeting the new guidelines, FHWA recently released guidelines establishing four categories for determining the level of effort needed to demonstrate a work-zone device's crashworthiness. "We recognize the varied character of work-zone traffic-control devices," said Artimovich. "As a result, three categories are being established for evaluating crashworthiness, along with a fourth category for trailer-mounted arrow and message signs."

Commonly used small, lightweight channelizing and delineating devices. These are devices that have been in common use for many years and are known to be crashworthy by crash testing of similar devices.

This category includes plastic or rubber cones and tubular markers, flexible delineator posts, and single-piece plastic drums without lights, batteries, signs, or other attachments. If ballast is used, it must be at ground level in accordance with the manufacturer's instructions.

To be included in this category, there must be virtually no potential for the device to penetrate windshields, cause tire damage, or have a significant effect on the control or trajectory of an impacting vehicle.

A request for acceptance does not need to be submitted for devices in this category: if the device meets a specification for which crashworthiness has been validated by crash or surrogate testing; or the device is accepted based on crash-test experience with similar devices. Simplified testing showing a device poses no risk to impacting vehicle occupants may be used to support the manufacturer's certification.

The simplified testing must include a written report by an independent, impartial observer, videotape documentation, and a means, other than the test vehicle's speedometer, for determining the vehicle speed at time of impact.

"There has already been quite a lot of testing of work-zone devices, but this information isn't general knowledge. FHWA has compiled results from numerous tests and will be issuing a memorandum that finds many work-zone devices acceptable for use without the need for additional testing," said Artimovich.

Potentially hazardous devices that produce no significant vehicle velocity change. Devices in this category may be substantial enough to penetrate a windshield or injure a worker, or they may cause vehicle instability when driven over if they become lodged under a vehicle. Testing to determine crashworthiness is required. However, devices weighing 45 kg or less may qualify for reduced testing requirements.

This category includes barricades, portable sign supports, intrusion detectors and alarms, and drums, vertical panels, or cones with lights.

"One of the biggest concerns ATSSA has is the possibility that all traffic-control companies will need to get their devices crash tested," said Ross. "We have many small companies in our industry and the costs of crash testing one or more devices could have a tremendous impact on them."

To address theses concerns, the FHWA has included a statement that a certain class of device (wood/metal barricades, for example) could be moved into Category 1 once sufficient testing is done to determine that the class of device is crashworthy.

Potentially hazardous devices that cause significant vehicle velocity change. Hardware expected to cause significant velocity changes to impacting vehicles must be tested to the full requirements of Report 350. Barriers, fixed sign supports, crash cushions, and other work-zone devices not meeting the definitions of the first two categories are included here.

Individual letters of acceptance will be issued by FHWA for crashworthy devices in this category.

Trailer-mounted attenuators. There are several work-zone devices that significantly increase the safety of traffic operations, but could cause great harm during an impact. These devices, usually trailer-mounted, include area lighting supports, flashing arrow panels, temporary traffic signals, and changeable message signs.

Even though accident experience to date show, that crashes with these devices are rare, FHWA believes they should be made crashworthy. Devices in this category should meet the recommended acceptance guidelines in Report 350 if they are to be used, unshielded, in the clear zone on the NHS. "However, we recognize the fact that current designs would most likely not meet Report 350's requirements for crashworthiness," said Artimovich. "And because we believe the current designs of these devices provide a net benefit to motorists, we have extended the compliance deadline to 2002 to give manufacturers time to develop crashworthy features."

A work zone's changing face

Depending on the outcome of crash testing for various devices, America's work zones could look very different in the near future. Devices the industry currently takes for granted could become obsolete, with new devices developed to meet the FHWA requirements.

"Imagine what will happen if traditional wood and metal barricades don't pass the test," said Ross. "Or if drums without lights were acceptable but drums with lights weren't. This ruling has the potential to significantly change the way we address work-zone traffic control."

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