Safety is an important goal of the 21st Century Truck Partnership (21CTP), with an overall objective to “promote the development and early adoption of technologies and processes to improve truck safety, resulting in the reduction of fatalities and injuries in truck-involved crashes, thus enabling benefits related to congestion mitigation, emission reduction, reduced fuel consumption, and improved productivity” (DOE, 2010). While working in concert with the U.S. Department of Energy (DOE) and truck manufacturers, the U.S. Department of Transportation (DOT), which has primary responsibility for safety, provides leadership for truck safety. Participating agencies within the DOT include the National Highway Traffic Safety Administration (NHTSA), with responsibility for safety regulations for all motor vehicles; the Federal Highway Administration (FHWA), with responsibility for highways, freight management, and operations; and the Federal Motor Carrier Safety Administration (FMCSA), with responsibility for developing federal regulations that promote commercial carrier safety and industry productivity. Presentations from all three agencies were given to the committee (see Appendix B) and are discussed throughout this chapter.
The 21CTP works collaboratively with the DOT to enhance vehicle safety. The overall goals of this collaboration are as follows (DOE, 2010):
1. “To ensure that advancements in truck design and technology to improve fuel efficiency do not have any negative impacts on safety.”
2. “Conversely, to ensure that efforts to improve safety do not reduce efficiency and, where possible actually contribute to improvements in overall motor carrier industry system efficiency.”
As discussed in the following sections of this chapter, the committee was unable to find any convincing case that technologies applied to reduce fuel consumption would degrade heavy-duty-truck safety. However, the wording of Goals 1 and 2 above could be interpreted by some that improving fuel consumption could be accomplished at the expense of sacrificing safety. The committee does not believe that this would happen, because the DOT and NHTSA have a primary focus on improving vehicle safety. Nevertheless, the Partnership might consider rewording these goals to be less ambiguous.
The DOT agencies all contribute to safety through their various areas of responsibility. The role of the NHTSA is to monitor highway safety in total (not just for heavy-duty trucks) and to conduct analysis to determine the potential benefit of vehicle safety systems, and to issue Federal Motor Vehicle Safety Standards (FMVSS) when appropriate.1 The Office of Freight Management and Operations of the FHWA strives to promote the efficient movement of freight and oversees the enforcement of federal regulations on the size and weight limits of trucks.2 The Federal Motor Carrier Safety Administration has as its mission to reduce crashes, injuries, and fatalities involving large trucks and commercial buses. The FMCSA is responsible for establishing safe operating requirements for commercial vehicle, drivers, carriers, vehicles, and equipment in interstate commerce.3
The FMCSA has set specific goals for truck and bus safety. These goals are set at fatality per 100 million vehicle miles traveled (VMT). In particular, the goals for 2007 through 2011 are as follows:
1 R. Kreeb, DOT, NHTSA, “Safety,” presentation to the committee, November 15, 2010, Washington, D.C.
2 R. Schmitt, DOT, FHWA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
3 L. Loy, DOT, FMCSA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
• 2007: 0.175 per 100 million VMT;
• 2008: 0.171 per 100 million VMT;
• 2009: 0.167 per 100 million VMT;
• 2010: 0.164 per 100 million VMT; and
• 2011: 0.160 per 100 million VMT.
(For comparison, it is noted that the fatality rate for all vehicle accidents in the United States in 2009 was 1.13 fatalities per 100 million VMT.4 The extent to which these and other goals have been met is discussed later in this chapter.
Finding 7-1. The wording of 21CTP Safety Goals 1 and 2 as now written might be subject to misinterpretation by some as allowing the compromise of safety in the effort to improve fuel consumption.
Recommendation 7-1. The Partnership should review the wording of its safety goals and consider rewording them so as to unambiguously state that safety will not be compromised in reducing fuel consumption.
Combination trucks (defined as tractor-trailer and single-unit trucks towing trailers) are involved in about 75 percent of the fatalities resulting from medium- and heavy-duty truck and bus accidents.5 In 2009, a total of 3,380 fatalities were due to large-truck crashes—this was a reduction of 20 percent from 4,245, the number of fatalities in 2008. Of the 3,380 fatalities in 2009, 2,551 were occupants in the other vehicle, and 503 were occupants of the truck (DOT, 2010b). It is typically the case that in truck accidents involving two vehicles, 75 percent or more of the fatalities involve the occupants of the other, usually smaller, vehicle. In accidents involving both a light vehicle and a large truck, the driver of the light vehicle is cited as being at fault most of the time, with some studies showing the driver of the light vehicle at fault as much as 78 percent of the time (see NRC  for more detail and additional references). Most of the fatal crashes involving trucks occurred in rural areas (64 percent), during the daytime (67 percent) and on weekdays (80 percent) (DOE, 2010).
Only about 300 fatalities occur each year in accidents involving truck Classes 5 and 6 combined, primarily because of their typically lower speed in urban daylight settings and many fewer miles traveled compared to Class 8 trucks (DOE, 2010).
Total fatalities for bus-related accidents in 2008 were 307, of which 41 were occupants in motor coaches.6 Commercial buses represent a very small percentage of fatal crashes, only 0.5 percent of the total. Very few fatalities occur due to school bus accidents. In 2009 occupants in a school bus had 3 fatalities, although 91 pedestrian fatalities were associated with school bus accidents.7
More details regarding the nature of heavy-duty-truck and bus accidents can be found in the NRC Phase 1 report (NRC, 2008, Chapter 7), on the NHTSA website, or in the University of Michigan Transportation Research Institute’s Trucks Involved in Fatal Accidents Database.8 Because the vast majority of fatalities and injuries associated with truck and bus accidents are due to combination-truck accidents, most of this chapter focuses on technologies that might reduce combination truck accidents.
Vehicle design and performance characteristics play an important role in truck crashes. The 21CTP places emphasis on technology that can enhance truck roll stability, improve braking performance, and reduce jackknifing. Additional crash avoidance technologies include driver warning, driver assist, and driver monitoring as well as onboard safety system monitoring (DOE, 2010). In addition, the DOT is exploring technologies to improve the frequency and thoroughness of in-service truck inspections. Many crash-avoidance technologies such as electronic stability control (ESC) and roll stability control are commercially available.
For research on heavy-truck safety, most of it devoted to crash-avoidance study, the NHTSA has an annual budget of about $2.1 million. The FMCSA budget is approximately $17.4 million, including analysis and research.
Several crash-avoidance technologies are addressed in this chapter: (1) braking and stability control, (2) collision warning, (3) safety system diagnostics, (4) driver behavior and performance, (5) smart roadside, and (6) intelligent transportation systems.
Braking and Stability Control
Material prepared by the NHTSA suggests that improved braking performance could reduce heavy-duty-truck accidents, particularly those for which the truck would rear-end another vehicle.9 In 2009, the NHTSA published a final rule on amend-
5 Unless otherwise noted, accident statistics cited in this chapter are for the United States.
6 L. Loy, DOT, FMCSA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
9 R. Kreeb, DOT, NHTSA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
ing FMVSS No. 121 to improve the stopping distance of trucks. By 2011, most new trucks will be required to have the capability to reduce their stopping distance 30 percent more than had previously been required. (This is an important improvement, but the stopping distance is still much longer than that of light-duty vehicles.) The improved braking performance can be accomplished by the use of larger drum brakes or air disc brakes. In time, the NHTSA would be expected to conduct field tests to assess the effects of this new braking requirement.
It should be noted that the field performance of antilock braking systems (ABSs) required by FMVSS No.121 on all air-braked vehicles of 10,000 lb or greater manufactured after March 1, 1997, has shown mixed results. In a comprehensive study published by the NHTSA in July 2010 (Kirk, 2010), it was found that there was a statistically significant 6 percent reduction in the number of crashes where ABS is assumed to be influential, and a large reduction in jackknives and off-road overturns; yet it was found that there was not a statistically significant reduction in fatal crash involvement. Although improved braking was influential in reducing the number of accidents as noted above, it is possible that accidents that are so severe as to cause a fatality cannot be avoided simply by improved braking. In addition, drivers need to be trained not to push the ABS technology to its limits.
Over the past 5 years, truck manufacturers have been offering electronic stability control on several truck models, and ESC has become standard on some truck models. DOE (2010) provides a detailed explanation of how ESC works. Because the application of stability control systems is fairly recent, there are insufficient real-world data to assess its effectiveness. However, studies have shown that the systems do offer potential for accident and fatality reduction. In Woodrooffe et al. (2009), crash scenarios were selected from national databases and examined to assess the potential benefit of stability systems on 5-axle tractor semitrailers. Assuming that all 5-axle tractor semitrailers were equipped with ESC systems, the expected annual safety benefit related to combined rollover and directional (yaw) instability is a reduction of 4,659 crashes, 126 fatalities, and 5,909 injuries.
Anticipatory automatic braking and speed control systems may also be used for accident prevention. However, these systems were not included in the materials prepared by or presented by the DOE or DOT, and therefore were not evaluated by the committee.
Advancements in collision warning systems for heavy-duty trucks have continued over the past several years. The 21CTP supports this area, because it may have potential for significant benefit in improving highway safety. Warning systems currently available include the following:
• Lane departure warning (LDW),
• Forward collision warning (FCW),
• Side object detection, and
• Rear object detection.
These systems use radar, video detection, ultrasonic, and other sensor systems combined with sensor input analysis algorithms to determine if a crash situation is developing, and then they warn the driver (DOE, 2010). Some systems not only warn the driver but also take control of the vehicle by de-throttling or braking.
In the NRC Phase 1 report (NRC, 2008, Chapter 7), it was reported that, based on field operational tests (FOTs) that had been completed at that time, LDW systems could potentially provide a reduction in accidents for single-vehicle roadway departure of a little more than 20 percent. In a more recent study, estimates were made of the cost-benefit potential of LDW systems (Houser et al., 2009). General Estimates System (GES) data were used to estimate outcomes from different lane departure crashes.10 Then, using information from the aforementioned field operational test, efficacy rates were determined in order to estimate the types of crashes that could be prevented using LDW systems. Assuming that the systems had been in place from 2001 to 2005, and recognizing that certain types of accidents could not have been prevented by LDW (e.g., loss of steering control from brake lock-up), it was estimated that the mean average annual preventable fatalities could be 147 and preventable injuries could be 2,642.
The DOT has taken an approach of integrating forward collision, rear-end impact, road departure, and lane changing warning systems into what it calls Integrated Vehicle-Based Safety Systems (IVBSS). This program also involves the University of Michigan Transportation Research Institute, Battelle, Eaton, PACCAR, Conway, Navistar, Takata, and the Michigan Department of Transportation. A field operational test was recently completed—it was a 10-month test involving 10 trucks and 20 drivers. Some key findings of the FOT were encouraging (DOT, 2010a):
• Drivers stated that the system made them more aware of the traffic environment;
• Most of the drivers would recommend the purchase of such a system, would prefer to drive a truck with such a system, and thought that such systems would increase driving safety; and
• Seven drivers said that the system potentially prevented them from having a crash.
In an independent evaluation of the FOT results, the John A. Volpe National Transportation Center estimated that the integrated system would be 11 percent effective in preventing accidents of the type targeted by IVBSS, and therefore could prevent, annually, 13,000 crashes involving trucks.11
Safety System Diagnostics
The DOT has two initiatives in the area of safety system diagnostics: tire pressure monitoring and brake systems diagnostics. Tire pressure monitoring systems have become common on light-duty vehicles and could be of particular importance for both safety and life-cycle costs if used on heavy line-haul trucks, particularly as the industry moves toward single wide-base tires. Properly inflated tires not only enhance safety and durability, but also reduce fuel consumption. In a recent study it was found that 1 in 14 tires was as much as 20 psi underinflated (approximately 20 percent of recommended pressure). This can lead to higher tire procurement costs, and it is estimated that underinflated tires on heavy-duty trucks results in fuel consumption increases of about 0.6 percent.12 Yet to date, only about 5 percent of the heavy-duty truck fleet has tire pressure monitoring systems.
The industry has been moving aggressively with more powerful braking systems. However, with 10 wheel ends on a typical tractor-trailer, brake maintenance is a challenge for most fleets and one of the highest-cost maintenance components. In general, there is no feedback to the driver until an emergency stop is necessary. A road-check study conducted in 2002 found that of the 49,032 vehicles checked at random, 22 percent were pulled out of service for noncompliance, and more than half of those pulled were because of brake-related issues (Lang, 2005).
In a study of the effectiveness of brake monitoring systems, the FMCSA conducted a field trial to evaluate several systems to measure brake stroke, shoe lining wear, and temperature on a fleet of buses: in-city buses were selected to provide a harsh braking protocol and because the fundamental brake design on transit buses is similar to that of heavy-duty Class 8 trucks. In general, the systems tested performed well (see Order et al., 2009, for more detail).
To date the market penetration of onboard brake monitoring systems on trucks is near zero, although there is some application (10 to 15 percent) of the systems on transit buses. Trucking and bus companies that have rigorous preventive maintenance inspection programs would not benefit sufficiently to justify the added cost of onboard systems. Currently there is no plan to introduce regulations requiring onboard systems. Instead, the FMCSA has added the use of Performance Based Brake Testers (Performance Based Brake Tester [PBBT] Test and Procedure Guidelines, Commercial Vehicle Safety Alliance Training Course, Revised January 2010) to the standard North America Vehicle inspection procedure (FMCSA, 2002).13
Driver Behavior and Performance
The FMCSA, with the help of the NHTSA, conducted a study to determine the causes of truck crashes (Craft, 2007). In 963 crashes involving trucks, from April 2001 to December 2003, there were 249 fatalities. Of the crashes studied, it was concluded that 87 percent were caused by driver behavior, that of either the truck driver or the driver of the other vehicle; 10 percent were caused by vehicle failure; and 3 percent were caused by the environment. (Of the vehicle failures, brake problems were most often cited.) Critical reasons for driver faulty behavior, in descending order of frequency, included the following: interruption of traffic flow, unfamiliar roadway, inadequate surveillance, driving too fast, illegal maneuver, inattention, fatigue, illness, false assumption about the other driver’s action, and distraction inside the vehicle. Impaired driver behavior due to alcohol and drugs also contributes to truck crashes, but in most cases involving a truck and a light vehicle, the driver of the light vehicle is the one who is impaired (DOT/NHTSA, 2006). However, in a study of driver distraction in commercial vehicles, it was found that drivers were engaged in non-driving-related tasks in 71 percent of crashes (Olsen et al., 2009). (The apparent difference between the two studies as to the frequency of “distraction” as a causal factor is due to the fact that in the Olsen et al. study, “distraction” included inattentiveness, drowsiness, and secondary driving tasks such as checking the rearview mirror.)
Clearly, driver behavior and performance are important factors in highway safety, and the DOT has for this reason put significant emphasis on the subject. It is beyond the scope of this report to cover in detail all the studies and programs in place on driver behavior, but a few highlights are addressed.
The NHTSA has engaged in a number of driver-distraction research studies, including an observational study of driver cellular telephone use; driver distraction with wireless communication systems and route guidance systems; and the impact of inattention on crash risk (DOE, 2010). The FMCSA has initiated a program to determine the effectiveness of onboard monitoring in reducing accident risk, including the observation of driver behavior, fatigue monitoring, lane departure warning, forward collision warning, and hours of service monitoring. Onboard monitoring systems will be installed in 270 trucks across three motor carrier fleets, to be deployed by 2011, with results from the field operational tests in 2013.14 In the meantime, President Obama, on October 1, 2009, issued an Executive Order, Federal Leadership on Reducing Text Messaging While Driving, stating that federal employees shall not engage in text messaging when driving government vehicles or in personal vehicles while
12 L. Loy, DOT, FMCSA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2011, Washington, D.C.
13 Personal communication regarding onboard brake testing from Bob Kreeb, NHTSA, and Luke Loy, FMCSA, to committee member Larry Howell, December 8, 2010.
14 L. Loy, DOT, FMCSA,,“Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
on government business.15 Moreover, in 2009, the FMCSA issued a rule, effective October 27, 2010, prohibiting texting by commercial drivers while operating in interstate commerce.16 Many states have banned texting and/or cell phone usage while a person is driving (GHSA, 2011).
The FMCSA is conducting research to improve the manner in which state, local, and federal officials interact with commercial vehicle operators and drivers at the roadside. The objective is both to improve the efficiency and comprehensiveness of operations and at the same time to ensure that operators are adhering to applicable regulations. As an example, Level 1 inspections include the examination of the driver’s license, medical examiner’s certificate and waiver, hours of service, seat belt, brake system, fuel system, lighting, and many other vehicle systems. A Level 1 inspection usually takes about 40 minutes (DOE, 2010). With about 4 million trucks in service, it is likely that many will go more than a year without being inspected because of the time required. Smart roadside will use wireless technology to transmit driver, vehicle, and carrier information, including an electronic hours-of-service log to an inspection station.17
Smart roadside Phase 1, concept development, was completed in 2008, and Phase 2, prototype testing, in 2009. Phase 3, field operations testing, is in progress and expected to be completed in 2011. In Phase 3, real-time and automated safety checks are being demonstrated. The data include driver identification, license status, and log information, as well as vehicle lights, brakes, and tires.18 This technology looks promising for ensuring that more trucks and drivers are operating safely.
Intelligent Transportation Systems
The vision of intelligent transportation systems is that every vehicle operating on the nation’s highways will be a sensor probe with the capability to communicate with all other vehicles (vehicle-to-vehicle, V2V) and with the infrastructure (vehicle-to-infrastructure). The objectives are to enhance traffic management, reduce congestion, enable on-road vehicle inspection by means of wireless transfer of data, and prevent crashes. Realization of this capability will require the installation of dedicated short-range communication devices at intersections, on roadsides, and within the vehicles (DOE, 2010). Specific truck-related applications would include the following:
• Electronic No-Zone, a V2V communication system that will allow the truck driver to be aware of nearby vehicles, including any that might be in blind-spot areas, and vehicles close to the truck will be made aware of the truck;
• Technology that will alert drivers that they are approaching a slowed or stopped vehicle; and
• Curve speed information to warn the driver if the truck that he or she is driving needs to slow down as it approaches a curve.
More information is available from the Intelligent Transportation Systems Joint Program Office of the U.S. DOT Research and Innovation Technology Administration.19
Finding 7-2. Vehicle crashworthiness and occupant protection systems have seen extensive deployment, have contributed greatly to improved highway safety, and have achieved extensive North American fleet penetration. The next important step is to prevent crashes altogether.
Recommendation 7-2. The committee supports the emphasis that the DOT and the 21CTP are giving to crash-avoidance technologies and recommends that crash-avoidance technologies continue to be given high priority and technical support.
The DOT recognizes that it may be possible to increase motor carrier efficiencies by allowing increases in commercial vehicle weight or trailer size. Consideration must be given to the potential of greater highway damage. Although heavy-duty trucks weighing more than 40,000 lb account for only 5 percent of total highway traffic, they account for more than 50 percent of highway damage.20 (Damage can be mitigated by distributing the load over more axles.) Safety could be an issue, too, although the use of heavier vehicles could be offset by a reduction in the total number of heavy vehicles on the road. The Transportation Research Board (TRB) has recommended additional study to assess the impact on highway safety of the use of heavier commercial vehicles and of longer or multiple trailers (TRB, 2010a). In any case, the National Research Council report Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles found that when allowed over the entire fleet, increasing vehicle size and weight could yield fuel savings of 15 percent or more (NRC, 2010). Fur-
16 See Docket No. FMCSA-2009-0370, Limiting the Use of Wireless Communication Devices, also, in the Federal Register, September 27, 2010 (Vol. 75, No. 186, p. 59118).
17 See http://www.fmcsa.dot.gov/facts-research/presentations/6_wireless_roadside_inspections_Loftus_vid_508.pdf. Dated March 4, 2008.
18 L. Loy, DOT, FMCSA, “Overview of DOT Truck Safety and Productivity Activities,” presentation to the committee, September 8, 2010, Washington, D.C.
20 J. Nicholas, DOT, FHWA, “Safety,” presentation to the committee, November 15, 2010, Washington, D.C.
ther, in that report, it is recommended that Congress give serious consideration to liberalizing vehicle weight and size (NRC, 2010, Recommendation 7-2, p. 177). A similar suggestion has been made by the TRB in the aforementioned study. To acquire real-world data, with the support of the FHWA, commercial truck weight pilot studies are being conducted in Maine and Vermont to assess the benefits as well as potential safety issues with road and bridge infrastructure as combination-vehicle weights up to 99,000 lb travel on the interstate system (DOE, 2010).
In 2009, there were 33,808 highway fatalities in the United States, the lowest number of deaths since 1950 (DOT, 2010b). Fatalities declined in 2009 from 2008 in all vehicle categories, including motorcycles, for which the number of fatalities had been increasing for the previous several years. For truck accidents in which there was a fatality, the total number of fatalities decreased from 4,250 in 2008 to 3,380 in 2009, a decrease of 20 percent. The goals of the FMCSA for reducing truck and bus fatalities per 100 million vehicle miles traveled were met in 2006 (target, 0.179; actual, 0.176); 2007 (target, 0.175; actual, 0.169); 2008 (target, 0.171; actual, 0.152); and 2009 (target, 0.167, actual, 0.121).
The significant decline in highway fatalities is certainly good news. There have been a number of studies aimed at identifying the contributions to the reduction. One potential contributing factor could be the recession that began in 2008. People typically travel less during a recession; in particular, nonessential travel is reduced. Data have confirmed a month-to-month reduction in fatalities during every recession going back several decades (DOT, 2010c). However, there is evidence that many other factors are contributing as well. In fact, there is a long-term trend of highway fatality reduction in spite of the up-and-down cycles associated with recessions (DOT, 2010c). During the past 10 years, there has been an increase in seat belt usage and continuing improvements in occupant protection systems in most vehicles, including the application of frontal and side air bags. Better occupant protection in light-duty vehicles could be contributing to the reduction of light-duty vehicle occupant fatalities in truck V2V accidents. Unfortunately, however, even with seat belt usage at about 85 percent, more than half of the passenger vehicle occupant fatalities in 2009 were unbelted (DOT, 2010b). Thanks to advocacy groups and stricter laws, the number of alcohol-related highway fatalities had declined from the 1980s into the 1990s, but that number has leveled off for the past decade at approximately 37 percent of all fatalities.21 Certainly, more rapid response of emergency vehicles plays an important role.
Clearly, significant progress in highway safety has been made in the United States, but when it comes to highway safety, there should always be efforts to strive to do even better. And there are additional opportunities. In a comprehensive study comparing U.S. progress in highway safety with that of other developed countries, the TRB found a number of areas that deserve further attention (TRB, 2010b). The TRB found that although the United States achieved a 19 percent reduction in fatalities from 1995 to 2009, other nations have done better. Annual traffic fatalities have declined in France by 52 percent and in the United Kingdom by 39 percent, for example. Traffic fatalities have declined by about 50 percent during that time span in 15 high-income countries. The reader is referred to the TRB (2010b) 188-page report for more detail, but a few highlights of the report’s conclusions are noted. First, at a general level, the TRB found that successful national safety programs are characterized by the overall management rather than by particular interventions. The elements of the management program include a systems perspective that integrates engineering design, traffic control, regulatory control, and public health methods to identify and reduce risk; specific goals and milestones, and accountability to meet those goals; and regular monitoring to measure progress and to identify problems. The report notes that the U.S. programs are typically deficient with respect to this ideal management model.
The Phase 1 NRC review of the 21 CTP recommended (NRC, 2008, Recommendation 7-1) that the 21CTP and the DOT should develop a prioritized list of all heavy-truck safety projects. The 21 CTP’s response to this recommendation (see Appendix C in this report) was that it could not be done because of the various independent federal agencies that are involved. Yet, the TRB has recommended an approach that would require a higher level of management integration by the DOT and the states than currently exists (TRB, 2010b). Although it is beyond the scope of this committee’s charge to make recommendations covering highway safety overall, it is clear that a more integrated management approach to highway safety would also be beneficial to truck safety and should be given serious consideration.
The TRB (2010b) report also notes specific suggestions that are worthy of consideration. In the area of alcohol-impaired driving, the TRB report notes that the legal blood alcohol content (BAC) limit is 0.08 BAC in the United States, whereas it is only 0.05 BAC or lower in Australia, Canada, Japan, and nearly every country in Europe. Fatalities in accidents in which alcohol was a factor have remained nearly constant, at about 37 percent of all fatalities during the past decade in the United States.22 The TRB report suggests that it may be possible to reduce alcohol-related fatalities by reducing the legal BAC limit and by enforcing it more strictly.
22 See http://www-fars.nhsta.dot.gov/trends/trendsalcohol.aspx. Accessed April 6, 2011.
Successful speed management programs in other countries target major road systems and use intensive enforcement. This has led to reduction in top speeds by from 3 to 4 miles per hour and is credited with an estimated fatality reduction of from 15 percent to 20 percent. Seat belt usage is another area assessed by the TRB study. Although the average seat belt usage in the United States is near 85 percent, it is more than 90 percent in most of the other nations studied in the TRB report. The TRB suggests that an increase in seat belt usage in the United States by 5 percent might save an additional 1,200 lives annually (TRB, 2010b). The TRB report offers suggestions for actions that state and federal agencies should consider in response to the report’s recommendations.
As noted earlier, the majority of accidents involving tractor-trailer combinations occur as a result of a smaller vehicle striking the tractor or trailer. A significant number of such crashes occur because a light-duty vehicle runs into the back of the trailer. In some cases, the smaller vehicle underrides the trailer, causing intrusion into the passenger compartment. The NHTSA issued a rule requiring the installation of structural guards on the back of trailers for the purpose of preventing underride. These guards were to have been installed on all trailers with a gross vehicle weight (GVW) of 10,000 lb or more, manufactured on or after January 24, 1998 (DOT, 2010d). The DOT (2010d) study found that the structural guards have had little success in reducing the number of fatalities that occur as a result of accidents in which a smaller vehicle rear-ends a trailer. More recent testing by the Insurance Institute for Highway Safety has shown that midsize cars impacting certain underride guards at closing speeds of 35 miles per hour can result in significant passenger compartment intrusion and that certain guards failed at speeds as low as 25 miles per hour.23 In the spirit of looking for additional opportunities, the committee suggests that the DOT explore the potential benefit of modifying the requirements for the structural guards going forward.
Finding 7-3. The DOT has met its heavy-truck safety goals for the past 4 years. However, the committee observes that the TRB’s 2010 study Achieving Traffic Saftey Goals in the United States: Lessons from Other Nations has shown that other nations have established more aggressive initiatives and goals with impressive results, and those results suggest that even greater improvement in highway safety is possible in the United States. The committee also notes that overall improvements in highway safety also yield improvements in heavy-duty truck safety, because most heavy-duty truck fatal accidents involve a light-duty vehicle.
Recommendation 7-3. The DOT should evaluate the conclusions and recommendations of the TRB study Achieving Traffic Saftey Goals in the United States: Lessons from Other Nations of highway safety in other nations, and consider the possibility of establishing more aggressive initiatives and goals for highway safety in general. The DOT should also consider establishing more aggressive goals for heavy-duty truck safety.
As noted in the section above titled “Overview of Goasl and Timetables,” an overarching goal of the 21CTP is to ensure that new systems and technologies to reduce truck fuel consumption do not degrade safety and that improvements in heavy-duty truck safety do not increase fuel consumption. As shown in Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, (NRC, 2010, p. 29), the primary energy losses of a heavy-truck- and-trailer combination are due (in decreasing order) to the power plant, vehicle aerodynamics, tire rolling resistance, auxiliary loads, and drivetrain. Modifications to the engine for reduced fuel consumption generally have no direct impact on vehicle safety.
Modifications for reduced aerodynamics drag typically include efforts to reduce the drag coefficient. The committee is aware of no negative impact on safety due to improved aerodynamic performance of heavy-duty trucks except for the potential of side panels on trailers or other devices falling off.
The primary goals for reducing rolling resistance are to ensure proper inflation pressures on existing truck tires and to eventually replace dual tires with single wide tires. Although it is worthwhile to further explore the potential changes in stopping distance in going to single wide tires, any changes most likely would be offset by new stopping distance requirements for heavy-duty trucks.
Highway accidents are often caused by excessive speed, which also increases aerodynamic drag and therefore fuel consumption. Thus, in this example, adhering to posted speed limits should both improve highway safety and reduce fuel consumption.
A reduction in highway accidents in general will reduce congestion due to the slowdown at the crash site. As noted in NRC (2008, Chapter 7), congestion is an important cause of increased and unnecessary fuel consumption; thus, reducing congestion-causing accidents will also reduce fuel consumption.
There is some possibility for interaction between fuel consumption and safety. For example, side panels on trailers and other devices for improving aerodynamics should be adequately secured to ensure that they do not fall off and present a road hazard. And the rear structural guards on trailers add weight to the trailer, albeit a very small percentage relative to the weight of the tractor-trailer combination. Should a next-generation wide-base single tire fail, it is
23 See http://iihs.org/externaldata/srdata/docs/sr4602.pdf. Accessed June 15, 2011.
possible that wheel damage could occur as the vehicle pulls off the roadway. These interactive effects are expected to be negligibly small. However, as vehicle manufacturers adopt new components and systems to reduce fuel consumption, it will be important for the DOT to monitor these and other vehicle modifications to ensure that safety issues do not emerge.
Finding 7-4. Some of the potential safety improvements considered by the committee may have negligible impact on fuel consumption and, in some cases, appear to have positive implications. However, further study of the potential highway safety impact of high productivity vehicles is warranted.
Craft, R. 2007. The Large Truck Crash Causation Study (LTCCS), Analysis Brief, LTCCS Summary. FMCSA-RRA-07-017. July. Washington, D.C.: Federal Motor Carrier Safety Administration.
DOE (U.S. Department of Energy). 2010. White Paper on Safety. Working draft, September 1, 2010. Updated 21st Century Truck Partnership Roadmap and Technical White Papers. Washington, D.C.: Office of Vehicle Technologies.
DOT (U.S. Department of Transportation). 2010a. Integrated Vehicle-Based Safety Systems: Heavy-Truck Field Operational Test, Key Findings Report. DOT HS 811 362. August. Washington, D.C.
DOT. 2010b. Highlights of 2009 Motor Vehicle Crashes. Traffic Safety Notes. DOT HS 811 363. August. Washington, D.C.
DOT. 2010c. An Analysis of the Significant Decline in Motor Vehicle Traffic Fatalities in 2008. DOT HS 611 346. June. Washington, D.C.
DOT. 2010d. The Effectiveness of Underride Guards for Heavy Trailers. DOT HS 811 375. October. Available at http://www-nrd.nhtsa.dot.gov/Pubs/811375.pdf.
DOT/NHTSA (DOT/National Highway Traffic Safety Administration). 2006. Large Truck Crash Causation Study: An Initial Overview. DOT HS 810 646. August. Washington D.C.
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