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7 change). Vehicular fatalities in the group of states that had ways was a safety problem, whereas 40% of drivers reported raised their speed limits to 75 mph and 70 mph were higher that speeding was a "big" safety problem. than expected as compared with fatalities in the states that did not change their speed limits. COUNTERMEASURES TO Similarly, a rigorous meta-analysis conducted by Elvik SPEED-RELATED CRASHES et al. (2004) included 97 different studies with a total of 460 estimates of the relationship between changes in speed It is evident from the literature that inappropriate speed is a con- and changes in the frequency of crashes or associated tributor to crashes; however, traditional approaches to reducing injuries and fatalities. Using the Power Model, this study drivers' speed behavior have been somewhat ineffective. assessed the relationship between speed and road safety. Enforcement, education, and training are the traditional and The study concluded there was a relationship between most widely used strategies for speed management. Although speed and the number of crashes and the severity of these secondary, and in some cases reactive, approaches can be crashes. The data suggest that speed is likely to be the sin- effective to a certain extent, it may be more effective to directly gle most important determinant in the frequency of traffic control the vehicle's speed. fatalities; a 10% reduction in the mean speed of traffic is likely to reduce fatal traffic crashes by 34% and have a greater Commercial Vehicle Speed Limitation in Europe impact on traffic fatalities than a 10% increase in traffic vol- ume. These data include all vehicles and are not specific to The first European Union (EU) legislation requiring speed large trucks. limiters was adopted in 1992 for large vehicles and extended to smaller commercial vehicles in 2002. There is now a While traveling above the posted speed limit or driving too single standard for all trucks of more than 3.5 tons and a single fast for conditions has been shown to increase crash exposure standard for all coaches of more than nine seats (J.-P. Repus- (i.e., risk), speed variance among vehicles sharing the same sard, Directorate General Energy and Transport, Unit E3-- road has also been shown to be correlated with vehicular crash Road Safety, European Commission, personal communication, risk. Lower speed variance is associated with fewer crashes Dec. 2007). (Finch et al. 1994; Kallberg and Toivanen 1998). Compliance with speed limits decreases speed variability among vehicles, According to the European Commission (Report from the which is associated with decreases in the frequency of road Commission . . . 2001), speed limiters were introduced to collisions and the severity of bodily injury (NCHRP Special improve safety and reduce environmental effects. The regu- Report 204 . . . 1984; Waller 1987). Vehicles traveling the lation was based on the following arguments: same speed have fewer interactions and make fewer lane changing and decelerating maneuvers in response to other ∑ Heavy commercial vehicles and motor coaches are vehicles. This has been shown to decrease interactions equipped with large engines to provide them with suf- between vehicles thereby reducing crash risk. ficient power to ascend uphill slopes when loaded; how- ever, when not loaded or descending, the vehicles' power Speeding Trends by Truck Drivers output capability may be greater than that needed to oper- ate safely and if unrestricted could pose an excessive risk Insurance Institute for Highway Safety (IIHS) ("Institute to vehicle performance in braking or tire performance. Supports Speed Limiters . . ." 2007) concluded that truck ∑ Lower speed results in fewer road crashes and fewer speeds are increasing on rural Interstates (pp. 5, 7): casualties on roads. ∑ Lower speed means reduced fuel consumption and vehi- In New Mexico, where the speed limit for trucks is 75 mph, the cle emissions. proportion of large trucks exceeding 70 mph increased from ∑ Driving at lower speed causes less wear and tear on the 27% in 1996 to about 43% in 2006. The percentage exceeding engine, brakes, and tires, thereby indirectly improving 75 mph more than doubled, rising from 4% to 10%. Truck speeds also increased substantially in Nevada, which has 75 mph road safety and environmental performance. speed limits on rural interstates. The proportion of trucks travel- ing faster than 70 mph increased from 29% in 1996 to 41% in 2006. During the same decade, the proportion of trucks topping Speed Limiters in Commercial Vehicles 75 mph jumped from 8 to 14%. Speed limiter devices have been around for decades. Virtu- The IIHS nationwide survey ("Institute Supports Speed ally all Class 8 tractors now come factory-equipped to limit Limiters . . ." 2007) indicated that 64% of drivers favor a speeds by means of a menu-programmable interface that can speed limiter requirement for large trucks. More than three- be code-protected to resist tampering by drivers. After-market quarters of respondents who favored speed limiters supported speed limiter devices exist as well. Recent technological a maximum speed limit below 70 mph. More than 80% of advances have allowed for the application of information drivers reported that speeding on Interstate highways and free- technology and modern communications to provide greater
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8 flexibility and broader possibilities to manage speed even in Comte et al. (2000) surveyed passenger car drivers' atti- changeable situations (e.g., adverse weather conditions and tudes with regard to speed limiters and found that respon- different posted speed limits) (Varhelyi and Makinen 2001). dents believed enforcement was more acceptable than speed limiters because it targeted those who excessively break the A 2006 study by Cantor et al. investigated the adoption of speed limit. However, they also indicated that enforcement safety technologies among the largest trucking firms in the was costly and ineffective and rated speed limiters as the United States. The study targeted the largest for-hire motor most effective means for reducing speed. carriers as the authors believed these operations had the great- est financial resources to adopt emerging safety technologies. The concept of intelligent speed adaptation (ISA) for pas- A total of 415 surveys were completed and returned; of these, senger cars has been studied extensively in Europe. These 60.4% reported adopting vehicle speed limiters in their fleets. activities are reviewed in Intelligent Vehicle Technology and The responding firms included 52 LTL operations, 179 with Trends (Bishop 2005), a comprehensive study describing truckload operations, and 131 with both LTL and truckload active safety systems activities worldwide, including ISA operations. Thus, the study indicated wide adoption of speed developments, forming the basis for the following review. limiters among the largest for-hire trucking fleets. The research for the book was based on project publications and discussions with project officials. In 1991, NHTSA's Commercial Motor Vehicle Speed Control Safety Report to Congress discussed devices available ISA calls for vehicles to be "aware" of the prevailing to control truck speed and their application in commercial fleet speed limit on roads and (at minimum) provide feedback to settings. The report was supportive of fleet applications of the driver when that speed is being exceeded or (at maxi- speed-monitoring and speed-limiting devices, but concluded mum) limit the vehicle's speed to comply with the speed that "there was not sufficient justification to consider requir- limit. When ISA first entered the intelligent vehicle (IV) ing all heavy trucks to be so equipped. Problem size statistics scene, it was considered an outrageous idea by those who suggested that the number of target crashes was low; for saw the driver's authority over speed as untouchable. At the example, approximately 30 fatal crash involvements per year same time, road safety experts were convinced that, if speeds for combination-unit trucks. This small crash problem size, were moderated, road fatalities would decrease. The concept together with uncertainties regarding the potential for crash that has gradually gained currency in Europe is of an advi- reduction, suggested that the benefits of mandatory speed lim- sory system that provides insistent feedback to the driver itation were questionable." when the speed limit is being exceeded. A strong motivator for such a system has come from increased enforcement of Beginning in 1992, heavy vehicles in the United Kingdom speed limits (and stiff speeding fines) over much of Europe were required to use speed limiters. According to Haggar (notably France), such that drivers are more likely to wel- (R. Haggar, U.K. Department for Transport, personal com- come a system that helps them avoid severe penalties. A brief munication, Nov. 2007) they found the introduction of speed review of ISA projects and applications in Europe is pro- limiters correlated with a significant reduction in the crash vided here. rate, as follows: When requirements for goods vehicles over 7.5 tons were intro- Sweden duced in the early 1990s the criticism was leveled that more vehicles travelling on motorways at the same maximum speed would reduce not improve safety. In fact this was not the case. Sweden pioneered the development and testing of systems to The accident involvement rate on motorways (per hundred mil- electronically assist drivers in maintaining the posted speed lion vehicle kms) for all heavy goods vehicles (HGVs) increased limit. The Swedish Road Administration (SRA) has been at from 18.5 in 1993 to 18.8 in 2005≠a 2% increase. This is signif- the forefront of research aimed at reducing speeding as part icant, because traffic increased by 36% over the same period. These figures include accidents involving HGVs between 3.5 of its Vision Zero initiative to completely eliminate road and 7.5 tons which were not (in 2002) required to be fitted with fatalities. SRA conducted a major research initiative from a speed limiter. The reduction in accidents for exclusively speed 1999 to 2002 in the cities of Umea, Borlange, Lidkoping, and limited vehicles was significant. All articulated HGVs were Lund. Approximately 5,000 ISA-equipped vehicles were speed limited after 1993 and the accident involvement rate for that vehicle class fell from 40 (per hundred million vehicle kms) driven by 10,000 drivers. The purpose of the research was to in 1993 to 30 in 2005--a 26% decrease. Other contributing fac- study driver attitudes and use of the ISA systems, road safety, tors may also have influenced that decline but speed limiters and environmental impacts, and define conditions for large- have apparently played a significant part. scale deployment of ISA. Speed Limitation in Passenger Cars Using roadside transponders and global positioning systems (GPS)/digital map techniques, the research team implemented Speed limitation in passenger cars has received significant provision of posted speed limit information and over-speed attention, particularly in Europe. Prior studies were examined warning functions. An active accelerator pedal was used to to identify areas of relevance to speed limitation in CMVs. communicate speed information to drivers. As a result of the
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9 test deployments, speed violations were reduced. The results market is growing, with more than 1,000 systems installed suggest that better road safety was achieved without length- thus far. ening travel times and ISA had an overall positive effect on the surrounding traffic. The results also showed that if every vehicle was equipped with ISA, a 20% reduction in serious France road injuries could be achieved. Although user acceptance was high, most users thought ISA should be mandatory so The French government conducted ISA experimentation and that ISA-equipped cars did not "stand out" in the traffic assessment to better understand driver acceptance and effects stream by traveling at a slower (although speed-limit compli- on driving behavior in a project called LAVIA: The French ant) speed. SRA is currently developing new measures, such Project of Adaptive Speed Limiter. The key objectives of the as instituting regulations for ISA, equipping the Swedish LAVIA (Limiter Adjusting to the Authorized Speed) project, government vehicle fleet with ISA and encouraging private which was completed in 2006, were: fleets to adopt ISA as a component of "Quality Assured Transport." ∑ Assess user acceptance and usage patterns for ISA with several different functional approaches, According to Svedlund (2007), it is more advantageous ∑ Assess changes in individual driving behavior, when ISA is introduced fleet-wide rather than in individual ∑ Measure the reductions of speed or gaps with regard to private cars. The advantages of fleet-wide implementation of the speed limits, ISA include: ∑ Measure system impacts on speed limit compliance as well as any detrimental effects (e.g., reduced vigilance), ∑ Economic incentives: lower speeds result in less fuel and consumption and lower maintenance costs. ∑ Assess through simulation the global collective impacts ∑ Existing policies: compliant speeds can easily be adopted on safety using field testing data. naturally into company policy. ∑ Mapmaking: some carriers are route-bound such that it A vehicle equipped with LAVIA identified the posted speed is not necessary to find speed limit maps covering a limit at any time within the region designated for the experi- larger area. ments. The authorized speed was encoded in an enhanced dig- ∑ Easier to integrate technology: this target group already ital map for every road within the defined area and location has the equipment to a much larger extent than private referencing was used to correlate the vehicle's location with the drivers, such as a communication infrastructure, posi- posted speed limit on the road being traveled. The project made tioning, and maps for fleet management. use of manual speed limiter devices already in production by ∑ Incentives to maintain the equipment: the benefits pro- Renault and PSA Peugeot CitroŽn. vided by ISA compel commercial operators to adequately maintain their equipment as compared with personal car The speed limit information was used by the on-board owners. controller to provide three different types of driver assistance: ∑ Greater willingness to pay: early, non-mass production systems are too expensive for private users. Commer- ∑ Advisory system: the system was activated at the driver's cial companies can see the system benefits sufficiently option. When enabled, a warning was displayed on the to invest in the systems. dashboard if the speed limit was exceeded. ∑ Goodwill: statements of intent by transport companies ∑ Voluntary active system: the system was activated at declaring their non-tolerance toward drugs, alcohol, the driver's option. However, when activated, the throt- and reckless driving will, in combination with the use tle was under LAVIA control and the speed limit could of alcolocks and ISA, clearly improve their image as a not be exceeded. reliable business. ∑ Mandatory active system: the system was always active, ∑ Monitoring: ISA systems can generate statistics useful with the throttle under LAVIA control. The speed limit for driver monitoring. could not be exceeded. Since the full-scale trial, Sweden has been working on a A fleet of 20 vehicles equipped with LAVIA were assigned strategy for large-scale implementation of ISA. Part of their to 100 drivers in the Paris area for normal usage in a radius of strategy focuses on the national quality-assured transport 200 km around their homes. Thus, many different road types project, which helps transport providers and purchasers to and substantial variation in posted speed limits were encoun- provide quality-assured transportation from a road safety and tered. Bishop (2005) reported results from the LAVIA project. environmental perspective. The initiatives undertaken by the A questionnaire of 1,000 drivers assessed driver's opinions SRA are intended to contribute to creating a market demand toward speed, safety, and speed limiters. Although there was for safe and environmentally sound transports. Key focus broad agreement with the idea of ISA, only 31% of respon- areas are speed, alcohol and drugs, seat belts, safe vehicles, dents favored having ISA in their car. However, Bishop and harmful emissions. Svedlund (2007) reports that the ISA (2005) concluded there was a strong potential to increase