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Tractor Trailer Underride - another look -
and another Author�s note: What follows is the complete, unedited manuscript -- with some added information -- that originally appeared in the Accident Reconstruction Journal (Sep/Oct, 1993). Reprinted with permission of the author. Although "tractor-semitrailer" is the more correct term, when the author uses the generic "semi," he means the entire rig, tractor included. Presented here with permission of the author. When I first broached the subject of "Trailer Underride, The Almost Always Fatal Collision" [LAW and ORDER, May 1988], the focus was on investigating the problem. My follow-up article, "Trailer Underride Revisited" [LAW and ORDER, August 1992], dealt with some solutions. Both studies had to do with tractor/trailers that (1) backed across a highway into a loading area; (2) pulled out of a driveway; (3) made a U-turn, (4) were being driven slower than normal; or (5) are stopped on or parked alongside an interstate highway. Motorists have difficulty perceiving and identifying the rigs (if they see them at all) in time to avoid crashing into them. Unsuspecting drivers and passengers suffer incapacitating or fatal injuries when their cars run under the side or strike the rear of a semitrailer. Visibility aside, there are other things that the trucking industry and safety officials can do to prevent the needless carnage of Trailer Underride. Some of these accidents occur when sleepy motorists drift off the edge of the roadway and run into the back of a parked or disabled tractor/trailer. In these cases, it makes little difference whether the trucker positioned safety triangles behind the trailer, had the 4-way flashers going, or if reflective tape emblazoned the rear of the trailer. In the instance of side underride, a vehicle might still strike an adequately marked trailer if the rig moved suddenly in front of a car that was too close for the driver to take evasive action. Once a vehicle hits a trailer, it doesn't matter how many lights or markings it has; the car still goes underneath. Should it? On rear end protection, Federal Motor Carrier Safety Regulation, Section 393.86, states: "Every motor vehicle, except truck tractors, pole trailers, and vehicles engaged in driveaway-towaway operations, the date of manufacture of which is subsequent to December 31, 1952, which is so constructed that the body or the chassis assembly if without a body has a clearance at the rear end of more than 30 inches from the ground when empty, shall be provided with bumpers or devices serving similar purposes which shall be so constructed and located that: (a) The clearance between the effective bottom of the bumpers or devices and the ground shall not exceed 30 inches with the vehicle empty; (b) the maximum distance between the closest points between bumpers, or devices, if more than one is used, shall not exceed 24 inches; (c) the maximum transverse distance from the widest part of the motor vehicle at the rear to the bumper or device shall not exceed 18 inches; (d) the bumpers or devices shall be located not more than 24 inches forward of the extreme rear of the vehicle; and (e) the bumpers or devices shall be substantially constructed and firmly attached." What that single-sentence mouthful says is that if the back of your trailer is more than 30 inches off the ground, put a bumper on it. Perhaps the rationale behind the 30 inches is that the hoods of most passenger cars (at windshield level) are between 35 and 40 inches above the ground; therefore, such cars couldn't fit under the back of a trailer. Not! One of the weakest parts of a car is the hood. At highway speeds of 55 miles an hour, or even at 30 mph, when a car runs into a semitrailer the hood peels back and exposes the car's front seat occupants to a crisis. The regulation does not address the strength or impact-absorbency of the bumper except to say that it must be "substantially constructed," whatever that means. Moreover, the rule says nothing about protective guards along the sides of trailers. According to the Insurance Institute for Highway Safety (IIHS) [Status Report, July 11, 1992] as many as 151 deaths in underride crashes may be occurring each year . . . [the] proposed 22-inch maximum ground clearance for rear underride guards is preferable to the 30 inches now allowed, but it's still way too high." And what about those "substantially constructed" bumpers? "Care should be taken so underride guards aren't completely rigid [as] automobile occupants are best protected by energy-absorbing guards." There are rear bumpers available with energy-absorbing features like hydraulic shocks or rubber blocks. The Institute also says the National Highway Traffic Safety Administration (NHTSA) should be addressing side underrides, noting that deaths in such crashes "are at least as common as those associated with rear underride crashes." "A coalition organized by the Citizens for Reliable and Safe Highways (CRASH) wants a much stronger truck underride standard than NHTSA is contemplating." [IIHS Status Report, Vol. 27, No. 7.] During a Washington, D.C. press conference, Joan Claybrook, Co-Chair of CRASH, noted that "Underride crashes occur when automobiles that run into the backs of huge trucks are squeezed underneath like so much toothpaste . . . With the car's force-absorbing bumpers and engine compartment sliding below the mass of the truck's body, the top of the passenger compartment hits the truck full force and is guillotined off like a knife through Crisco." Members of the coalition include not only CRASH but representatives from Advocates of Highway and Auto Safety, the American Academy of Pediatrics, the American Insurance Association, the Center for Auto Safety, the Consumer Federation of America, the Institute for Injury Reduction, the National Association of Governors' Highway Safety Representatives, the National Head Injury Foundation, Public Citizen, and the Trauma Foundation. [Ibid.] CRASH's working agenda calls for antilock brakes, on-board recorders, and splash/spray suppression devices, plus rear and side impact guards. Those guards should be designed to "reduce crash forces on occupants of passenger vehicles striking the rear ends and sides of single-unit and combination trucks." [CRASH Newsletter, Vol. 2, No. 2.] The coalition also wants only 16 inches of ground clearance on the rear bumper instead of 22. Many automobile bumpers, however, are less than 14 inches above the ground, so lowering an impact-absorbing rear trailer bumper to 14 inches might be better. The vertical center of the car's bumper (in line with the frame) should match the lower bumper plate on the rear of the trailer. According to the coalition, too many trucks would be exempt from NHTSA's proposed standard. Therefore, the group wants the underride requirements to apply to straight trucks weighing more than 10,000 pounds as well as to tractor/trailers. Some good news: On January 18, 1996 (for trailers manufactured after that time), the DOT lowered the rear bumper height from the ground from the earlier 30 inches to 22 inches. Advocates such as CRASH wanted them lower, but some improvement is better than no improvement. Thus far, this article covered tractor/trailers, the drivers of which probably thought what they were doing was just fine. Truckers who figured it was okay to back across a poorly lit road or park on the emergency berm of an interstate highway. But how many truckers stop their big rigs along a highway because the driver is tired (as opposed to mechanical troubles with the truck)? A 1985 Commercial Vehicle Safety Alliance study found that 41 percent of all truck crashes had fatigue as a probable contributing circumstance. Many of those crashes end with a jackknifed tractor/trailer being crosswise in the road. The initial collision renders the electrical system inoperative and the single, double--and even triple trailers--completely block all lanes. A prime target for a subsequent underride accident. While the rule-makers at NHTSA contemplate changes to the Federal Motor Carrier Safety Regulations, what can law enforcement do to stem the tide of underride collisions? A recent survey found that 19 percent of truck drivers questioned admitted to falling asleep at the wheel at least once in the month prior to the survey. Log books, commonly called "Lie Books," "Joke Books" or "Cheat Sheets" may show a driver has been behind the wheel a couple of hours when actually it's been several. When you ask to see a trucker's log book, ask for the other one, too. During an accident investigation, don't stop looking when you find a log book in the truck cab. Chances are, another is secreted between or under the seats or in the sleeper berth. Explore the truck cab for gas receipts. Many such receipts list the date AND TIME of a fuel purchase. If, when on patrol, you see a semi parked along the highway, check it out. Is the rig disabled or is the driver taking a nap? Parking at the edge of the road because the driver is sleepy may seem like an emergency to the driver, but it's an underride accident waiting to happen. If nothing else, escort the outfit to the nearest exit or, on a non-interstate highway, to an area where the driver can park the rig and not present a hazard. Notify the trucking company and keep a record of the date, time, and the name of the person with whom you spoke. Many reputable trucking companies have specific guidelines about improper parking but safety directors or company officials won't learn of the incident unless an accident occurs or someone tells them about the situation. The driver certainly isn't going to admit any wrong doing so it's up to the police officer to let trucking company officials know what's going on. In the event of an accident, investigators should advise drivers and officials what could have been done to prevent the accident or lessen the injuries. If the DOT bumper collapses in a rear-end collision, perhaps the bumper was not "substantially constructed." Investigators should inspect tail lamps and side-marker lamps to determine if they were off or on at impact. If you, as the at-scene investigator, do not know how to make such a lamp examination, preserve the bulb(s), using proper evidence-collection methods, for someone who does. When a moving vehicle strikes a stopped semi in the rear, it shoves the semi forward. However, if the trucker set trailer brakes, the possibility is good that the tires left marks on the pavement. Document those marks with measurements and photographs. This documentation helps place the location of the rig in relation to the edge of the road. In any underride accident, whether the semi was moving or stationary, photograph the sides and rear of the trailer. If the marker lamps are off, note it in your report before you take flash photos. Often it will appear in pictures that the lamps were lit due to a reflection of the camera's flash. Note whether the trailer has retroreflective tape or paint. Keep in mind that most semitrailers--with a few exceptions--manufactured after December 1, 1993, must be outfitted with retroreflective tape, in mandated patterns and colors, on both the rear and sides. Organizations such as CRASH urges its members--and this could include accident investigators whether a member or not--to keep pressure on the Federal Highway Administration (FHWA). You're encouraged to express opposition to weakened hours-of-service restrictions for truck drivers and to let FHWA know about trailer underride accidents where better bumpers or the presence of side guards would have prevented death or at least lessened injuries. Granted, many motorists who have underridden the rear or side of a semitrailer had a bit too much to drink. However, nighttime trailer underride crashes usually involve sober drivers. Older drivers have difficulty discerning distances between them and a truck ahead. By the time motorists perceive a stopped or slow-moving truck, they do not have enough time or distance to stop or swerve. A friend who knew of my profound interest in the trailer underride phenomenon thought maybe I was overstating the problem. "I mean," he said, "just how hard can it be to see an object nearly as big as a house in front of you?" Then one night, on an ordinary two-lane road, he happened to glimpse a piece of a dark object barely miss his hood and pass by his driver's side rear view mirror. He looked back over his shoulder in time to see that the front of his car had passed under a corner of a semitrailer. My friend was lucky. He noted later that the trailer's clearance lights were on but apparently they were dirty enough that he simply saw nothing until the trailer was but two or three feet in front of him. Police who patrol our streets and highways must realize how practically impossible it is to distinguish huge trailers at night, especially in pursuit cases. One of Indiana's Finest, responding to an officer-needs-help call, completely underrode a semitrailer that made an illegal turn across a 4-lane, undivided highway. His squad car went under one side of the trailer; half the car came out the other side. There was not one inch of pre-collision skidmarks. Accident investigators will find, when in court on underride crash cases, "experts" for the other side may testify that a particular roadway was free from obstructions and that the victim should have seen the offending vehicle--and could have avoided the collision. That's partially true. Motorists probably can see a certain distance away but that doesn't mean they will perceive or recognize a distant object as a hazard. The FHWA commissioned Biotechnology to perform time/distance studies regarding the underride situation. Those studies' results show that a driver "with average reflexes, eyesight, decisiveness and sobriety, driving an average car" [at 60 miles an hour] will take almost THREE seconds to see and recognize a hazard [e.g., the back of a semitrailer], almost SEVEN seconds to decide on a course of action, and almost 4.5 seconds to complete a maneuver. This is not to say that the "rule of thumb" to allow 100 feet of stopping distance for each 10 mph, is entirely invalid. But at night, when a tractor-semitrailer blocks the road, motorists must identify the problem when they are one-quarter mile away. In the 14.5 seconds necessary to see, perceive (recognize), decide what to do, and then do it, a vehicle will travel 1,276 feet. If the recognition begins a quarter mile away (1,320 ft), the motorist has a "cushion" of 44 feet. That quarter mile is what's called the "Decision Sight Distance," and it's based on nighttime traffic traveling at 60 mph. I worked a case that involved a tractor and a dirty white box-type trailer. The truck driver had missed his destination, stopped along the edge of a two-lane road, at night, and decided to turn around. He backed his rig across the highway into an intersecting county road. Although he saw two approaching cars, he assumed he could finish backing before they got close enough to be a problem. Wrong. When the semi was midway through the maneuver, the lead car slammed into the trailer in front of the rear duals. The weather was misty and the roadway was damp. A woman in the second car saw the semitrailer when the headlights of the car in front of her illuminated the side of the trailer. However, she testified that she did not recognize it as a hazard for she thought it was merely a heavy patch of fog. An "expert," called by the trucking company, measured the available distance the victim had to see the semi and concluded that she should have seen it. Keep in mind it was dark and misty, there were no ambient lights, the tractor faced the car from the opposing lane and the tractor's headlights made it look as though the rig was in its proper lane. Moreover, the semi was in a rural area and in a position a reasonable and prudent motorist would not expect, crosswise and blocking both lanes and shoulders. Another underride case involved a semi that pulled out of a truck stop onto a four-lane divided highway. When the tractor was in the median crossover, the trailer extended back across the two lanes between the truck stop and the median. A motorist came along and underrode the trailer. This time there was no fog and the incident occurred by a truck stop (where motorists could expect to find trucks entering and leaving). The tractor's headlights did not shine toward approaching traffic and the trailer bore all proper DOT lights and reflectors. However, the same "expert," hired by the motorist this time, concluded there was no way the woman in the car could have seen the trailer. Go figure. Often a question arises about whether it would be beneficial to a case to perform a video "reenactment." Besides the obvious dangers, use care to operate quality equipment. Assuming the location is protected and all the vehicles are in place, don't merely prop a camcorder on someone's shoulder and start shooting. Nighttime videotaping often proves ineffective. It is quite difficult to replicate in a camera what the human eye perceives--or doesn't--at night. Take care to assure that lighting on the tape represents accurately the conditions at the scene. Many times during a video session, people unscrupulously or unwittingly adjust the gain (light intensity or amplification) on the camcorder to see what's going on in the view finder. This affects the amount of light recorded on tape. Though it's a simple matter to play back the recording on the camcorder, the view screen is so tiny it's not going to give a full sense of how the same picture will look on a television screen. With the introduction of too much light, oncoming headlights may resemble locomotive beacons; if insufficient light gets recorded, people watching the tape may believe it was darker that it really was. Another problem with camcorder taping is the lens. A regular lens captures a specific area in a particular depth of field. The only way to see more area is to pan the camera left or right or zoom out. If this camera movement is too fast, it is difficult to follow when watching the tape. The human eye makes a panoramic sweep in an instant; therefore, a person at the accident site may see more peripherally than that shown on the video. Further, in a clinical situation (reenactment), when a person knows ahead of time what he or she will see when watching a video, an object may be perceived earlier because the person expects to see it. The same object may not have been recognized at the time of the accident because the driver did not anticipate the object. Other problems, inherent in still photography, exist with video taping. Many police departments routinely make videos of accident scenes. Use them as a supplement to- not a replacement of- still pictures. Photograph vehicles without using a flash attachment (use a tripod for time exposures) and take additional photos with a flash. Don't just shoot closeups. Take pictures from drivers' perspectives. Take similar photos in daylight. Trailer underride accident cases usually end in litigation. Don't harbor a feeling during an investigation that the cause of the collision is cut-and-dried and will never go to court. Murphy's Law says it will. For more on the topic, read "Trailer Underride: Conspicuity, Human Factors and Rear Bumpers" by Joseph E. Badger, published by The Institute of Police Technology & Management (IPTM), University of North Florida, 4567 St. Johns Bluff Road, South; Jacksonville, FL 32224-2645.
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