THE National Transportation Safety Board has recommended that side underride guards be required on trailers with GVW ratings above 10,000 pounds.

In a letter to dated April 3, the National Transportation Safety Board (NTSB) urged the National Highway Traffic Safety Administration to require guards that would protect passenger cars from running under trailers. The NTSB also is asking NHTSA to require side underride protection on highway tractors rated above 26,000 pounds GVW.

The NTSB cites General Estimates System (GES) reports that say 43,629 police-reported collisions occurred between 2005 and 2009 in which passenger vehicles collided with the sides of trailers. The NTSB also cited a NHTSA reported that said large truck side impacts comprised 15% of fatal two-vehicle collisions between large trucks and passenger vehicles during 2011. Other research indicated that passenger vehicle collisions with the sides of tractor-trailers resulted in more than 15,000 injured persons during 2001-2003, the NTSB said.

The board also wants changes to existing rear underride regulations. The NTSB concluded that passenger vehicle occupant injuries caused by rear underride accidents could be reduced by making changes to guard design. The NTSB recommends that NHTSA revise requirements for rear underride protection systems for newly manufactured trailers with GVWRs over 10,000 pounds. The recommendation is based in part on recent crash testing that included offset crashes.

Additionally, NTSB recommends that NHTSA add trailer VIN and trailer model year to the Fatality Analysis Reporting System database for trailers with GVWRs over 10,000 pounds.

“Although the majority of collisions involving the sides or rears of tractor-trailers consist of impacts to the trailers, police reports provide less information for trailers than for other types of motor vehicles,” Deborah A P Hersman, NTSB chairman, wrote in her letter to NHTSA. “This is reflected in police accident report forms: few include spaces for the vehicle identification number (VIN) or license plate numbers of trailers. Also, the forms do not instruct police officers to fill in this information for trailers.”

Side underride

In its letter the NHTSA, the National Transportation Safety Board cited a NHTSA report that said 15% of all large truck fatalities involved passenger cars striking the sides of either the tractor or trailer.

“Side underride occurs when passenger vehicle bumpers are not at the same height and do not engage the substantial side structure of tractor-trailers,” NTSB said in its letter. “Side underride collisions are an important safety problem because they defeat crumple zones and prevent air bag deployment, both vital safety advances in improving protection of passenger vehicle occupants during crashes,” the NTSB said. “Airbags will not deploy in some underride collisions when the sensors to trigger them are not contacted by vehicle structures. Crumple zones do not work as intended in underride collisions when relevant passenger vehicle structures fail to engage tractor-trailer structures.”

According to an analyst last year of Large Truck Crash Causation data involving injuries or fatalities, here is what happens when a car and truck collide from the side, including sideswipes and angle collisions:

•  Side underride occurred 69% of the time with trailers, but cars also underrode the sides of tractors 44% of the time.

•  Passenger compartments were intruded more than 60% of the time.

•  The vehicle contacted a truck or trailer axle in 74% of the injury cases.

•  Police reports indicate that underride occurs 59% of the time in cases where the axles are contacted.

A side solution?

NTSB believes potential solutions exist.

“There appear to be some promising technical solutions to protecting passenger vehicle occupants from being injured in side underride collisions with tractor-trailers,” Hersman wrote. “A 2009 project funded by the European Commission designed and tested a side underride guard for trailers that prevented passenger vehicle compartment intrusion from side underrides. “A side underride protection system on trailers was also developed and tested in the United States. It prevented passenger compartment intrusion and reduced the likelihood of head, chest, neck, and femur injuries.

Some European researchers have proposed systems that would modify frames of trailers as an alternative to side underride guards. According to Hersman, at least one manufacturer has sold trailers with a protective frame that is designed to mitigate both rear and side underride collisions.

NTSB recognized that different designs aimed at preventing side underride may be required for tractors and trailers.

“The NTSB recommends that NHTSA require that newly manufactured trailers with GVWRs over 10,000 pounds be equipped with side underride protection systems that will reduce underride and injuries to passenger vehicle occupants,” Hersman wrote. The NTSB also recommends that NHTSA require that newly manufactured truck-tractors with GVWRs over 26,000 pounds be equipped with side underride protection systems that will reduce underride and injuries to passenger vehicle occupants.”

Changing rear underride guards

NTSB also urged NHTSA to develop more rigorous requirements for rear underride guards for trailers.

According to NTSB research, trailers get rear-ended about 3,065 times a year, resulting in approximately 19% of car-truck fatalities. Of those collisions, 75% involve passenger cars.

The NTSB’s issue with the current rear underride standard is that guards that comply still yield when struck outboard of the vertical member.

Citing an analysis of the Large Truck Crash Causation Study, the letter said 20 of 30 accidents in which passenger cars struck a post-1998 guard resulted in passenger compartment intrusion. The study attributed the intrusion to either striking only the outer edge of the guard, failure of the attachment system, or the buckling of the trailer frame so that the guard was out of position.

“The NTSB recommends that NHTSA revise requirements for rear underride protection systems for newly manufactured trailers with GVWRs over 10,000 pounds to ensure that they provide adequate protection of passenger vehicle occupants from fatalities and serious injuries resulting from full-width and offset trailer rear impacts,” Hersman wrote.

Gathering trailer data

The NTSB believes better regulatory decisions can be made if more data can be obtained. At present, few police accident reports contain a space for either the vehicle identification number (VIN) of the trailer. Much of the information that traffic safety researchers can be determined through the VIN or the trailer license plate—which can be traced back to identify the VIN.

“Also, the forms do not instruct police officers to fill in this information for trailers,” Hersman wrote. “Having accurate trailer data is important for evaluating the effects of safety regulations and for determining the safety of trailer designs. If trailer data were available in federal and state databases, analyses could be done to determine whether certain trailer designs and equipment should be altered to reduce injury risks. Due to the lack of trailer data in federal and state databases, such studies cannot currently be done without extensive cost and time for data collection.”

While all the above relates to trailers, the NTSB began its letter to NHTSA discussing ways to improve driver visibility. According to the NTSB, there were 457 reported accidents involving trucks and pedestrians between 2005 and 2009. Most (60%) involved the front of the truck. In many instances, the truck driver was unaware that he had run over a pedestrian until alerted by someone who witnessed the accident.

The NTSB is paying particular attention to the right side of tractor-trailers, where accident rates tend to be significantly higher.

Among the measures NTSB is considering:

•  Enhanced mirror systems. According to a 2007 study, large trucks that did not have mirrors on the right fender were disproportionately involved in crashes that resulted in deaths and injuries.

•  Crossover convex mirrors are currently required by state law on large trucks operating in New York City, and the European Union also has requirements for enhanced mirrors on large trucks to reduce the size of blind spots.

•  Advanced technologies to detect vehicles and vulnerable road users in blind spots are also in development and some versions have been installed on selected passenger vehicles for the past few model years, including systems that brake automatically upon sensing pedestrians at the front or rear.

•  Side-view assistance systems that use sensors to monitor the blind spot in the adjacent lane and provide an audio warning if there is a vehicle in the blind spot after the driver signals an intention to change lanes.

•  Rear-vision assistance systems, consisting of cameras and monitors that allow drivers to see pedestrians and passenger vehicles in the rear blind spot while drivers are backing their vehicles.

The NTSB recommended that NHTSA require newly manufactured truck-tractors with GVWRs over 26,000 pounds to be equipped with visibility enhancement systems to improve the ability of drivers of tractor-trailers to detect passenger vehicles and vulnerable road users, including pedestrians, cyclists, and motorcyclists. ♦