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U.S. Department of Transportation http://www.nhtsa.dot.gov National Highway Traffic Safety Administration DOT HS 809 222 NHTSA Technical Report March 2001 The Effectiveness of Retroreflective Tape on Heavy Trailers This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161. The United States Government does not endorse products or manufacturers. Trade or manufacturers’ names appear only because they are considered essential to the object of this report. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. DOT HS 809 222 4. Title and Subtitle 5. Report Date The Effectiveness of Retroreflective Tape on Heavy Trailers March 2001 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Christina Morgan 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Evaluation Division, Plans and Policy National Highway Traffic Safety Administration Washington, DC 20590 11. Contract or Grant No. 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Department of Transportation National Highway Traffic Safety Administration Washington, DC 20590 NHTSA Technical Report 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract This report evaluates the effectiveness of retroreflective tape in enhancing the visibility of heavy trailers and reducing side and rear impacts by other vehicles into these trailers during dark conditions. It is based on a statistical analysis of 10,959 crash cases investigated by the Florida Highway Patrol and the Pennsylvania State Police in 1997 - 1999. The tape is quite effective. It reduced side and rear impacts into trailers, in dark conditions (including "darknot-lighted," "dark-lighted," "dawn," and "dusk") by 29 percent. In "dark-not-lighted" conditions, the tape reduced side and rear impact crashes by 41 percent. Tape is especially effective in reducing injury crashes. In dark conditions, it reduced side and rear impacts that resulted in fatalities or injuries to drivers of any vehicle by 44 percent. 17. Key Words 18. Distribution Statement retroreflective tape; heavy trailers; tractor-trailer combination vehicles; statistical analysis; evaluation; side and rear impacts; conspicuity; visibility Document is available to the public through the National Technical Information Service, Springfield, Virginia 22161 19. Security Classif. (Of this report) 20. Security Classif. (Of this page) Unclassified Unclassified Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 21. No. of Pages 63 22. Price TABLE OF CONTENTS TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v INTRODUCTION AND BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 HISTORY AND RESULTS OF EARLIER EFFECTIVENESS STUDIES .............................................................2 1.2 FMCSA RETROFIT STANDARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 CURRENT STATUS OF TAPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 CONSPICUITY DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 SUPPLEMENTARY FORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 CONSPICUITY DATA BASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3 CRASHES NOT INVESTIGATED BY STATE POLICE . . . . . . . . . . . . . . . . 20 BASIC ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 THE BASIC ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 STATISTICAL SIGNIFICANCE AND CONFIDENCE BOUNDS . . . . . . . . . 3.4 TAPE EFFECTIVENESS IN SPECIFIC DARK CONDITIONS . . . . . . . . . . . 3.5 COMBINED EFFECTIVENESS AND “BEST” ESTIMATES . . . . . . . . . . . . 23 23 26 29 32 33 TAPE EFFECTIVENESS IN SPECIFIC SITUATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 EFFECTIVENESS BY COLLISION TYPES . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 EFFECTIVENESS BY ENVIRONMENTAL/ROADWAY CONDITIONS . . . 4.3 EFFECTIVENESS BY TRACTOR/TRAILER CHARACTERISTICS . . . . . . 4.4 EFFECTIVENESS BY OTHER DRIVER/VEHICLE CHARACTERISTICS ............................................................ 4.5 EFFECTIVENESS BY CRASH-LEVEL INJURY SEVERITY . . . . . . . . . . . . 4.6 TAPE EFFECTIVENESS DURING THE DAYLIGHT . . . . . . . . . . . . . . . . . . 39 40 42 44 BENEFITS OF CONSPICUITY TAPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 CRASHES AVOIDED PER YEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 NONFATAL INJURIES AVOIDED PER YEAR . . . . . . . . . . . . . . . . . . . . . . 5.3 LIVES SAVED PER YEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 51 52 52 46 48 49 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 iii ACKNOWLEDGMENTS I would like to acknowledge Glenn G. Parsons, retired NHTSA employee, who started this evaluation. He designed the study and the data form; contacted the states and established working agreements with the Florida Highway Patrol and the Pennsylvania State Police. I would also like to acknowledge the officers of the Florida Highway Patrol and the Pennsylvania State Police who collected the data, without which this report would not be possible. Ed Bleakly of the Florida Highway Patrol and Sergeant John Rigney of the Pennsylvania State Police managed the data collection effort in their states, submitted the forms to NHTSA, and coordinated the project with NHTSA. iv EXECUTIVE SUMMARY All heavy trailers manufactured on or after December 1, 1993 must be equipped with red-andwhite retroreflective tape, sheeting and/or reflex reflectors around the sides and rear to make them more conspicuous. The National Highway Traffic Safety Administration (NHTSA) established this requirement, with its various options, in December 1992 by amending Federal Motor Vehicle Safety Standard (FMVSS) No. 108, “Lamps, Reflective Devices, and Associated Equipment.” However, retroreflective tape has been used almost exclusively for meeting the standard, and it is the subject of this evaluation. Heavy trailers are at least 80 inches wide and have a Gross Vehicle Weight Rating over 10,000 pounds. The purpose of retroreflective tape is to increase the visibility of heavy trailers to other motorists, especially in the dark. At those times, the tape brightly reflects other motorists’ headlights and warns them that they are closing on a heavy trailer. In the dark, without the tape, many trailers do not become visible to other road users until they are dangerously close. The alternating red-andwhite pattern flags its bearer as a heavy trailer and at the same time helps other road users gauge their distance and rate of approach. This report evaluates the effectiveness of the tape in reducing side and rear impacts into heavy trailers - primarily in dark conditions where even a vigilant motorist might not see an untreated trailer in time to avoid a crash, and secondarily in daylight, where the tape might alert inattentive drivers that they are approaching a trailer. In March 1999, the Federal Highway Administration extended the application of this important protection to the entire on-road trailer fleet by directing motor carriers engaged in interstate commerce to retrofit heavy trailers manufactured before December 1993 with tape or reflectors. These older trailers must have some form of conspicuity treatment, by June 1, 2001, in the locations specified by the NHTSA standard for new trailers, except on the rear impact guard. In other words, as of June 2001, almost all heavy trailers on the road will have some form of conspicuity treatment. This Federal Motor Carrier Safety Regulation furthermore gives motor carriers until June 1, 2009 to retire their pre-1993 trailers or retrofit them with treatments that conform exactly to the NHTSA standard (again, with the exception of the rear impact guard). Since none of NHTSA’s crash data at hand (FARS, NASS, or State files) identified whether crash-involved heavy trailers had retroreflective tape, NHTSA worked out agreements with the Florida Highway Patrol (FHP) and the Pennsylvania State Police (PSP) to collect data for this analysis. For a two-year period, each time these agencies investigated a crash involving a tractortrailer and filed a crash report, they also filled out an “Investigator’s Supplementary TruckTractor Trailer Accident Report” on every trailer in the crash. The FHP collected 6,095 crash cases from June 1, 1997, through May 31, 1999. The PSP collected 4,864 crash cases from December 1, 1997, through November 30, 1999. The analysis estimates the reduction of side and rear impacts by other vehicles into tape-equipped trailers in dark conditions - relative to the number that would have been expected if the trailers v had not been equipped. It is based on tabulating and statistically analyzing crash involvements of tractor-trailers by three critical parameters: (1) whether or not the trailer is tape-equipped; (2) the light condition - dark (comprising “dark-not-lighted,” “dark-lighted,” “dawn” and “dusk”) vs. daylight; and (3) relevant vs. control-group crash involvements. Relevant crash involvements are those where another vehicle crashed into the side or rear of a heavy trailer, because the tape can help the other driver see and possibly avoid hitting the trailer. The control group consists of single-vehicle crashes of tractor-trailers (where visibility of the tractor-trailer to other road users is not an issue at all) and impacts of the front of the tractor into other vehicles (where conspicuity of the side and rear of the trailer is also not an issue). The principal conclusion of the study is that retroreflective tape is quite effective, and it significantly reduces side and rear impacts into heavy trailers in the dark. Other findings and conclusions are the following: ANNUAL BENEFITS OF CONSPICUITY TAPE • When all heavy trailers have conspicuity tape, the tape will be saving an estimated 191 to 350 lives per year, preventing approximately 3,100 to 5,000 injuries per year, and preventing approximately 7,800 crashes per year, relative to a hypothetical fleet in which none of the trailers have the tape. CRASH REDUCTIONS BY LIGHTING CONDITIONS • In dark conditions (combining the subsets of “dark-not-lighted,” “dark-lighted,” “dawn,” and “dusk”), the tape reduces side and rear impacts into heavy trailers by 29 percent. The reduction is statistically significant (confidence bounds: 19 to 39 percent). • However, the tape is by far the most effective in dark-not-lighted conditions. Here, the tape reduces side and rear impacts into heavy trailers by 41 percent. The reduction is statistically significant (confidence bounds: 31 to 51 percent). • In dark-lighted, dawn, and dusk conditions, the tape did not significantly reduce crashes. The tape also did not significantly reduce crashes during daylight. CRASH REDUCTIONS FOR SPECIFIC SUBGROUPS IN DARK CONDITIONS The effectiveness estimates here are the percentage reductions of various subgroups of the side and rear impacts into heavy trailers in dark conditions. As stated above, tape reduces these crash involvements by 29 percent, overall. vi • The tape is especially effective in preventing the more severe crashes, specifically, injury crashes. Impacts resulting in fatal or nonfatal injuries to at least one driver are reduced by 44 percent. • The tape is more effective when the driver of the impacting vehicle is young. The crash reduction is 44 percent when the driver of the impacting vehicle is 15 to 50 years old, but only 20 percent when that driver is more than 50 years old. A possible explanation of this difference is that older drivers are less able to see, recognize and/or react to the tape in time to avoid hitting the trailer. • The tape may be somewhat more effective in preventing rear impacts (43 percent) than side impacts (17 percent) into trailers; however, this difference is not consistent in the two states. • The tape is effective in both clear (28 percent) and rainy/foggy weather conditions (31 percent). • The tape is especially effective on flatbed trailers (55 percent). These low-profile vehicles must have been especially difficult to see in the dark before they were treated with tape. • Dirt on the tape significantly diminished its effectiveness in rear impacts. Clean tape reduces rear impacts by 53 percent but dirty tape by only 27 percent. STATUS OF TAPE IN THE 1997-1999 CRASH DATA • Almost 50 percent of the pre-standard trailers in the study had retroreflective tape. The retrofit of these older, pre-1993 trailers was already well underway in 1997 - 1999. • More than 60 percent of the trailers with retroreflective tape had clean tape at the time of the study. About 30 percent of the trailers with tape had some dirt and less than 5 percent had “very dirty” tape. • About 96 to 99 percent of the retroreflective tape on the side of trailers was intact, while 92 to 95 percent of the tape on the rear of trailers was intact. vii viii CHAPTER 1 INTRODUCTION AND BACKGROUND In September 1992, the National Highway Traffic Safety Administration (NHTSA) amended Federal Motor Vehicle Safety Standard (FMVSS) No. 108, "Lamps, Reflective Devices, and Associated Equipment," by adding a Conspicuity Systems provision. This revision, effective December 1, 1993, requires that heavy trailers (i.e., those 80 or more inches in width with a Gross Vehicle Weight Rating over 10,000 pounds) manufactured on and after this date be equipped with reflective material. Two types of material are permitted -- (1) retroreflective sheeting, or tape, and (2) reflex reflectors. A combination of the two types is also permissible. However, retroreflective tape has been used almost exclusively for meeting the standard, and it is the subject of this evaluation. Essentially, the tape must outline the bottom of the sides of the trailers and the top corners, bottom and underride guard of the rear of the trailers. The tape must be applied in a pattern of white and red color segments to the sides and rear of the trailer and in white to the upper rear corners of the trailer. Specifications for affixing the tape to the sides and rear of the trailers are contained in Title 49, Part 571, Section 108 of the Code of Federal Regulations (i.e., 49 CFR 571.108). The purpose of the regulation is to make heavy trailers more conspicuous to other motorists. Studies of highway crashes where other motor vehicles collide with combination trucks (truck tractor plus heavy trailer) have indicated that, in a number of these crashes, the operator of the other vehicle may not have seen the combination truck in time to avoid a collision. Such crashes are more likely to occur in dark conditions or under other conditions of decreased visibility -- i.e., adverse weather conditions such as rain, snow, or fog. The light reflection qualities of the tape, particularly from sources such as automobile headlamps, enhance the conspicuousness of the heavy trailer, thereby also increasing the chances that the attention of other drivers in the vicinity will be directed to the combination truck. It is hoped that the tape, with its alternating red-white pattern, will also help those drivers more accurately assess the closing rate and distance between their vehicle and the combination truck. The tape is expected to be more effective in dark conditions, when combination trucks are harder to see, than during daylight. The amount of light should also influence the effectiveness of the tape. The tape should be more effective on unlighted dark roads than on lighted roads, or during dawn or dusk when some light is available. The tape should also reduce collisions into the rear and side of combination trucks especially in dark conditions, since the tape is on the side and rear of trailers. In rear impacts, your headlights will shine on the rear of the trailer and illuminate the tape, so you can detect the vehicle and avoid a collision. In side impacts where you are moving exactly or nearly perpendicular to the combination truck and especially if the combination truck is moving slowly or stopped, the tape is expected to be highly effective. In this case, your headlights will illuminate the side of the trailer and you may have enough time to avoid the collision. The tape may be less effective in preventing 1 sideswipe crashes where you are moving parallel to the combination truck. In this case, the angle between your headlights and side of the trailer may be too small to illuminate the tape. The tape is unlikely to have an effect in collisions with the front of the combination truck or on any singlevehicle crashes of combination trucks. The Government Performance and Results Act of 1993 and Executive Order 12866 (October 1993) require agencies to conduct periodic evaluations to assess the effectiveness of their existing vehicle safety standards. This report evaluates the effectiveness of retroreflective tape on heavy trailers required by FMVSS 108 (Lamps, Reflective Devices, and Associated Equipment). This evaluation will show if the tape reduces the number of side and rear impacts to trailers in dark conditions. Throughout the remainder of the report, a truck tractor pulling one or more trailers -- i.e., tractor with semi-trailer, full trailer, or two trailers will be referred to as a combination truck, retroreflective tape will sometimes be referred to as tape, and heavy trailers will sometimes be referred to as trailers. 1.1 HISTORY AND RESULTS OF EARLIER EFFECTIVENESS STUDIES Several early studies of combination truck crashes concluded that increasing the conspicuity of heavy trailers in dark conditions would reduce some of these crashes. Minahan and O’Day analyzed fatal car into combination truck crashes in Michigan and Texas and found that such crashes usually occur in the dark with frequent car underrides1. They concluded that the driver of the other vehicle did not detect the presence of the combination truck in time to avoid a collision. On the basis of these findings, it was concluded that improvements in the conspicuity of heavy trailers might reduce the frequency and severity of these crashes. Another analysis of the collisions of cars with tractor-semitrailers, based on the 1977 Fatality Analysis Reporting System (FARS), also found that such collisions are overrepresented in dark conditions and concluded the addition of lights or reflective paints on trucks and trailers would reduce the frequency of collisions2. In 1980, the agency initiated a three-phase research project to develop and evaluate an optimal configuration of heavy-truck and truck-trailer markings and lights. Phase I of this project entailed 1 Minahan, D. J. and O’Day, J., Car-Truck Fatal Accidents in Michigan and Texas, University of Michigan Highway Safety Research Institute, Report No. UM-HSRI-77-49, Ann Arbor, MI, 1977. 2 Green, P., et al., Accidents and the Nighttime Conspicuity of Trucks, University of Michigan Highway Safety Research Institute, Report No. UM-HSRI-79-92, Ann Arbor, MI 1979. 2 analyzing the problem of other vehicles striking large trucks and trailers.3 The work included interviewing trucking company representatives, analyzing crash data, modeling driver behavior, and analyzing active lighting and passive reflective material. The results indicated that crashes in which conspicuity might conceivably have been a factor were equally distributed between daylight and dark conditions and involved collisions with both the sides and rear of the trailer. Rear impacts tend to occur when the combination truck is traveling straight ahead and moving slowly, stopping or stopped on the roadway. The following driver either 1) does not see the combination truck at all, 2) sees the combination truck but misjudges its motion and/or distance, or 3) correctly perceives the combination truck’s dynamics and distance, but too late. Moreover, collisions of this sort are more severe in dark conditions. Side impacts most often occur when the combination truck is turning or being astride lanes, e.g. backing, making U-turns, etc. Sideswipe crashes often occur while the combination truck is traveling straight. Phase II entailed conducting a series of laboratory and field studies to determine the best way to mark heavy trailers and improve other drivers’ abilities to: 1) quickly and accurately identify combination trucks in the traffic stream, 2) judge their rate of closure, and 3) estimate their distance from combination trucks.4 The most effective marking scheme identified in these studies consisted of a strip of alternating colors outlining the side and rear perimeters of the trailers and a U-shaped outline of the mudflaps. Phase III of the research project was a fleet study to evaluate the crash reduction effectiveness of the reflective tape to the sides and rears of commercial trailers.5 The study, conducted by Vector Enterprises, Inc., took place over a 23-month period in 1983-1985. A total of 3,820 van trailers were selected for participation; half were treated with retroreflective tape; the other half served as a control group against which the performance of the treated trailers was compared. However, because of cost considerations, 1,910 treated van trailers in the study were equipped with less reflectorized material than that recommended by the Phase Two study. The Vector conspicuity scheme used alternately hatched red and white or blue and white, two-inch wide strips of retroreflective tape to outline the lower side rail on both sides of the trailer and the rear perimeter of the trailer. Each of the two groups accumulated 106 million miles of exposure during the study period. The study concluded that tractor-trailer combinations in the treated fleet were struck by 3 Burger, W. J., et al., Improved Commercial Vehicle Conspicuity and Signalling Systems, Task I – Accident Analysis and Functional Requirements, NHTSA Report No. DOT HS 806 100, Washington, DC, 1981. 4 Ziedman, K., et al., Improved Commercial Vehicle Conspicuity and Signalling Systems, Task II – Analyses, Experiments and Design Recommendations, NHTSA Report No. DOT HS 806 098, Washington, DC, 1981. 5 Burger, W. J., et al., Improved Commercial Vehicle Conspicuity and Signalling Systems, Task III – Field Test Evaluation of Vehicle Reflectorization Effectiveness, NHTSA Report No. DOT HS 806 923, Washington, DC, 1985. 3 other vehicles 15 percent fewer times than were combinations in the control fleet; the report did not distinguish side from rear impacts. The results of the fleet study were found to vary somewhat according to the number of crashes considered to be relevant -- that is, the number of crashes whose occurrence could be considered to have been affected by the conspicuousness of the trailer. After extensive review and reanalysis of the fleet test results, including solicitation of viewpoints from the public, NHTSA concluded that the potential benefits from retroreflective marking of heavy trailers were sufficient to warrant such a requirement under FMVSS 108. From its final review of the field test analyses, the agency estimated that the use of the material would reduce crashes into the side and rear of combination trucks in dark conditions by 15 percent and 25 percent, respectively.6 It was also estimated that injuries and fatalities in these crashes would be reduced by 15 percent. A study7 sponsored by NHTSA defined the large truck conspicuity enhancements that ought to be used as a basis for the revised Federal regulations. The study recommended the retroreflective tape width, color, pattern, and placement. The study also recommended the appropriate retroreflective efficiency level, taking into account the effects of environmental dirt, aging, and orientation of the marked vehicle. The current NHTSA standard generally incorporates these recommendations. 1.2 FMCSA RETROFIT STANDARD On March 31, 1999, the Federal Highway Administration (FHWA) published a final rule amending the Federal Motor Carrier Safety Regulations (FMCSRs) to require motor carriers engaged in interstate commerce to install retroreflective tape or reflex reflectors on the sides and rear of trailers manufactured prior to December 1, 1993. The final rule gives motor carriers until June 1, 2001, to install some form of conspicuity treatment in the same locations that NHTSA requires manufacturers to install such treatments, with the exception of the rear impact guard. Motor carriers have until June 1, 2009, to install conspicuity treatments identical to that required on new vehicles, with the exception of the rear impact guard. Effective January 2000, the authority for issuing and enforcing FMCSRs was transferred to a new agency within the Department of Transportation, the Federal Motor Carrier Safety Administration (FMCSA) There are two notable differences between NHTSA’s standard for new trailers manufactured on or after December 1, 1993 and FMCSA’s retrofit requirement for trailers manufactured before 6 Preliminary Regulatory Evaluation - Proposed Amendment to FMVSS No. 108 to Require Retroreflective Material on the Side and Rears of Heavy Trailers, NHTSA, Washington, DC, 1991. 7 Olsen, P. L., et al., Performance Requirements for Large Truck Conspicuity Enhancements, NHTSA Report No. DOT HS 807 815, Washington, DC, 1992 4 December 1, 1993. The NHTSA standard requires an alternating red and white pattern. FMCSA encourages the use of a red-and-white pattern, but allows flexibility in terms of colors or color combinations from June 1, 2001 through June 1, 2009. After June 1, 2009, these trailers, if they are still in service, will have to have the red-and-white pattern. The second difference is that on the rear, NHTSA requires two red and white applications, one the full width of the vehicle and the other the full width of the underride guard. The FMCSA requires only the full width of the vehicle. A standardized appearance will assist motorists so that they can quickly recognize the image of the reflective tape in the dark and associate it with a trailer. Therefore, it alerts motorists to the presence or motion of the trailer, even if the body of the trailer is not visible. 1.3 CURRENT STATUS OF TAPE Table 1-1 shows the percentage of trailers that have tape and the percentage of trailers with FMVSS 108 tape by state and calendar year. The percentage of trailers with tape is increasing over time. This suggests that the retrofitting of trailers with tape is proceeding. An observational study by NHTSA staff in 1996 found about 60 percent of the combination trucks had trailers with tape. The vehicles were observed at a weigh station along a major interstate in two states, Florida and Pennsylvania. By 1999, almost 70 percent of the trailers had tape in Florida and almost 80 percent in Pennsylvania. The 1997-1999 data is from a recent study of truck-trailer crashes collected to evaluate the effectiveness of conspicuity tape. Florida collected data from June1, 1997, through May 31, 1999 and Pennsylvania from December 1, 1997, through November 30,1999. Therefore, the Florida 1999 data is from only the first five months of the year, while the Pennsylvania 1999 data is from almost the full year, January through November. (See Chapter 2 for more information about the conspicuity data.) TABLE 1-1 Observational and Conspicuity Crash Data Trailers by Tape Configuration, State, and Calendar Year Total Trailers With FMVSS % of Trailers w/Tape Trailers With Tape 108 Tape that meet FMVSS 108 Florida 1996 (Observed) 1997 (Crashes) 1998 1999 Pennsylvania 1996 (Observed) 1997 (Crashes) 1998 1999 453 1,904 3,224 1,275 271 1,060 2,002 863 60% 56% 62% 68% 181 962 1,864 811 40% 51% 58% 64% 67% 91% 93% 94% 1,116 298 2,457 2,430 632 206 1,745 1,908 57% 69% 71% 79% 500 191 1,612 1,776 45% 64% 66% 73% 79% 93% 92% 93% 5 Table 1-2 shows the percentage of pre-standard trailers (trailer model year less than 1993 that are not required to have tape until June 1, 2001) that have tape and the percentage of pre-standard trailers with FMVSS 108 tape by state and calendar year. The observational data cannot be separated by model year and are not included in this table. Here, there is a 10 percentage point increase in the trailers with tape in Florida from 1997 to 1999. In Pennsylvania, there is an 8 percentage point increase from 1998 to 1999. The 1997 Pennsylvania data is from only one month, December, and is not a large enough sample to accurately represent the status of trailers with tape. TABLE 1-2 Pre-1993 Trailers by Tape Configuration, State, and Calendar Year Total With FMVSS 108 % of Trailer w/Tape Trailers With Tape Tape that meet FMVSS 108 Florida 1997 1998 1999 Pennsylvania 1997 1998 1999 1,091 1,711 660 417 715 317 38% 42% 48% 349 622 283 32% 36% 43% 84% 87% 89% 108 725 654 60 339 360 56% 47% 55% 54 289 310 50% 40% 47% 90% 85% 86% Table 1-1 and 1-2 also shows the percentage of trailers with tape that meet FMVSS 108 requirements. In Table 1-1, the 1996 data is noticeably different than the later years in the percentage of trailers with tape that meet the 108 standard. In the 1996 observational survey, the tape had to meet the NHTSA standard exactly, while the tape had to meet or be similar to the standard in the 1997-1999 crash data. The criteria the police officers used to judge whether the tape was similar or dissimilar to FMVSS 108 is not known. In 1999, about 93 percent of all trailers with tape have tape that meets the NHTSA standard or is similar to the standard. Table 1-2 shows that about 86 percent of the retrofitted trailers with tape in 1999 have tape complying with FMVSS 108 although not required until 2009. Thus, a large majority of trailers with tape already have a standardized appearance. 6 CHAPTER 2 CONSPICUITY DATA Typically, studies to assess the effectiveness of a vehicle safety standard consist of the collection and analysis of highway crash data which compare the experience of vehicles that meet the safety standard with the experience of vehicles that do not meet the standard. For most evaluation studies, this is a comparison of the crash experience of vehicles built before the effective date of the given standard with the crash experience of the vehicles built subsequent to the effective date of the standard. All trailers manufactured on and after December 1, 1993, are required to be equipped with the retroreflective material. Retroreflective tape was the primary choice of material. However, many trucking firms equipped their new trailers with the special tape prior to the December 1993 effective date of the NHTSA requirement. Companies have added reflective tape to their older (i.e., pre-December 1, 1993, manufacture) trailers since the NHTSA conspicuity requirement was issued and in response to FMCSA retrofit standard. Therefore, it was necessary to obtain more information on the crash-involved trailer than just its date of manufacture (which can be derived from the trailer Vehicle Identification Number or VIN). It was necessary to observe directly whether or not the trailers were equipped with retroreflective tape. None of the existing NHTSA crash data sets (FARS, NASS CDS, NASS GES, or the State data) identify whether or not a crash involving heavy trailers had this tape. NHTSA had to collect and create a new data set containing this essential data element. 2.1 SUPPLEMENTARY FORM NHTSA created the “Investigator’s Supplementary Truck-Tractor Trailer Accident Report” form to collect the necessary tape information on trailers. Most of the supplementary elements pertain only to the trailer (or trailers) being pulled by the truck tractors. Other data items collected on the form besides the presence of retroreflective tape are: (1) whether or not the application pattern conforms to the FMVSS 108 requirement, (2) the color(s) of the tape, (3) the condition of the tape with respect to the presence/accumulation of dirt or other agents which could degrade the reflectivity, (4) whether the tape is damaged or has missing segments, (5) the weather conditions at the time of the crash, (6) the light conditions (i.e., dark, daylight, dusk, etc.) at the time of the crash, (7) the date, time, and day of week of the crash, (8) the county, city, road and speed limit of the crash, and (9) the state accident report number, to allow eventual linkage to the state crash file. 7 The supplementary form was commonly referred to as the “NHTSA Green” because it was printed on green paper. A copy of the NHTSA Green form is on Page 9 and the instructions for the form are on Page 10. Other data elements describing the crash are also required for this analysis such as: (1) the crash configuration (i.e., other vehicle into combination truck rear, other vehicle into combination truck side, etc.). (2) a diagram/narrative explanation of the crash. (3) estimates of damage to the other vehicle, and to the combination truck, in descriptive terms. (4) injuries and fatalities resulting from the crash. (5) contributing factors or other conditions surrounding the crash (alcohol, speeding, fail to yield, etc.). These data elements are routinely collected on Police Accident Report (PAR) forms. Therefore, data from both the NHTSA Green and the basic PAR forms were necessary for this analysis. The Florida Highway Patrol (FHP) and the Pennsylvania State Police (PSP) agreed to collect the necessary data for this analysis. For a two-year period, each time they investigated a crash involving a tractor-trailer and filed a PAR, they also completed a NHTSA Green form on every trailer in the crash. A tractor-trailer combination was defined as a truck tractor pulling one or more trailers -- i.e., tractor with semi-trailer, full trailer, or two trailers. Only crashes investigated and reported by these agencies were included in the study. Crashes where the PAR was filed by local police, sheriffs, other police agencies, or the drivers themselves were not included. In 1998, the FHP collected 59 percent and the PSP collected 60 percent of all crashes involving a tractor trailer in their States. See Section 2.3 for a discussion on crashes not investigated by state police and how this will not significantly affect our effectiveness estimates. For each crash reported, the FHP and the PSP provided NHTSA with a copy of the State PAR and the respective NHTSA Green stapled together, with the NHTSA Green displaying the same accident report number as the State report. The FHP collected data from June 1, 1997, through May 31, 1999. The PSP collected data from December 1, 1997, through November 30, 1999. 8 2.2 CONSPICUITY DATA BASE A contractor created a data base with the necessary information to evaluate the safety benefits of retroreflective tape. The contractor entered all the data elements on the NHTSA Green and some of the elements on the PAR. Only the pertinent data elements on the PAR were entered such as: initial point of impact, vehicle type, vehicle maneuver, first harmful event, driver age, driver sex, etc. The most important data elements were coded directly from the hard-copy data to avoid a delay in analyzing the data, since the states’ automated PAR files are usually not available at NHTSA until 6 to 9 months after the end of the year. The remaining elements on the PAR could be analyzed later, if needed, by linking the conspicuity data to the automated state data files at NHTSA. The state accident report number on the NHTSA Green permits us to match the conspicuity cases to the corresponding state data cases for this purpose. The conspicuity data contain one derived element, besides the elements on the forms. The derived element identifies the specific location on the vehicle of the first impact if it was not identified on the PAR. In both states, the point of impact is an element on the PAR. In Florida, the police can mark “Trailer,” or “Unknown” if applicable. Point of impact is “Trailer” in 16 percent of the tractor-trailer combinations and is “Unknown “ in 5 percent. In Pennsylvania, point of impact is “Towed Unit” in 5 percent and is “Unknown “ in 1 percent of the tractor-trailer combinations. These codes are too general for this analysis and do not say if the trailer was hit in the rear or the side, a crucial distinction for this report. Thus, if the point of impact is “Trailer,” “Towed Unit,” or “Unknown,” the data coder used all available information on the PAR including the diagram and the narrative to classify the specific location on the trailer of the first impact as one of the following: No Damage, No Impact, Non Collision or Not Applicable Front Right Side Rear Left Side Top Undercarriage Other Unknown 11 The conspicuity data base was organized into three files for each state: the crash file, the vehicle file, and the pedestrian file. The crash file contains information describing the environmental conditions and roadway characteristics at the time of the crash. The vehicle file contains information describing the vehicles and their drivers involved in the crashes. The pedestrian file contains information describing any pedestrians involved in the crashes. Table 2-1 shows the number of crashes, vehicles, and pedestrians on the conspicuity data base by state. TABLE 2-1 Conspicuity Data Base: The Number of Cases by State and File Crashes Vehicles Pedestrians Florida 6,095 12,380 51 Pennsylvania 4,864 9,134 25 Total 10,959 21,514 76 Since each crash had to include at least one tractor-trailer combination, more than half of the vehicles are tractor-trailer combinations. Table 2-2 shows that 52 percent of the Florida vehicles are combination trucks and 59 percent of the Pennsylvania vehicles are combination trucks. Tractor-Trailer Combination Other Vehicles Total Vehicles TABLE 2-2 Vehicle Types by State Florida 6,444 52% 5,936 48% 12,380 100% Pennsylvania 5,349 59% 3,785 41% 9,134 100% Total 11,793 9,721 21,514 State regulations in both Florida and Pennsylvania allow truck tractors traveling in their state to pull one or two trailers. Table 2-3 shows that most tractors pulled one trailer. TABLE 2-3 Tractor-Trailer Combinations by Number of Trailers and State Number of Trailers Florida Pennsylvania One Trailer 6,363 99% 5,191 97% Two Trailers 81 1% 158 3% Total Vehicles 6,444 100% 5,349 100% 12 Total 11,554 239 11,793 Table 2-4 compares the characteristics of the trailers in Florida and Pennsylvania. For the most part, the trailers were similar: vans were the most common type, followed by flatbeds. The trailer model years were also similar: slightly more that half of the trailers in Florida are pre-standard, not required to have tape. (Most of the unknown model years in Pennsylvania are probably model years before 1981. In Pennsylvania, trailer model year is decoded from the trailer VIN. Model years earlier than 1981 cannot be decoded from the VIN since the VIN was not standardized before 1981.) The most noteworthy difference is that 60 percent of the trailers in Florida were equipped with tape, while 70 percent in Pennsylvania were equipped with tape. This is partly due to the data collection starting and ending six months later in Pennsylvania, by which time more trailers had been retrofitted. TABLE 2-4 Number and Percent of Trailers by Trailer Characteristics and State Florida Pennsylvania Trailer Type Van 3,414 52% 3,655 66% Flatbed 1,174 18% 847 15% Tanker 580 9% 348 6% Dump 550 8% 218 4% Auto Transporter 163 2% 60 1% Other/Unknown 644 10% 379 7% Trailer Year Pre-Standard < MY 1993 3,504 54% 1,504 27% Transition Year MY 1993 349 5% 254 5% Transition Year MY 1994 442 7% 376 7% Post-Standard > MY 1994 2,022 31% 1,865 34% Unknown 208 3% 1,508 27% Treatment Tape 3,925 60% 3,859 70% No Tape 2,478 38% 1,326 24% Unknown 122 2% 322 6% Table 2-5 shows the characteristics of the trailers with tape by state. Almost all have the tape applied to the side and rear of the trailer as required by FMVSS 108 or similar to the standard. (The criteria the police officers used to judge whether the tape was similar or dissimilar to FMVSS 108 is not known.) About 90 percent or more have the required alternating red and white tape. Very few trailers have tape that is “very dirty.” About 30 percent of the trailers have tape that is somewhat dirty. The extent, if any, to which dirt on the tape may reduce its effectiveness will be analyzed in Chapter 4. 13 TABLE 2-5 Tape Characteristics on Trailers Equipped with Tape Florida Pennsylvania Tape Pattern FMVSS 108 or Similar 3,627 92% 3,579 93% Other 223 6% 202 5% Unknown 75 2% 78 2% Tape Color Red/White 3,676 94% 3,477 90% White, Orange, or Blue 157 4% 267 7% Other/Unknown 92 2% 115 3% Tape Condition Rear No Tape* 10 0% 22 1% Clean 2,575 66% 2,440 63% Some Dirt 1,103 28% 1,226 32% Very Dirty 167 4% 117 3% Unknown 70 2% 54 1% Tape Peeling/Missing on Rear of Trailer No Tape* 10 0% 22 1% Not Peeling, Missing 3,565 91% 3,612 94% Peeling, Missing 330 8% 196 5% Unknown 20 1% 29 1% Tape Peeling/Missing on Rear Underride Guard of Trailer No Tape* 11 0% 22 1% Not Peeling, Missing 3,634 93% 3,654 95% Peeling, Missing 250 6% 131 3% Unknown 30 1% 52 1% Tape Peeling/Missing on Rear of Trailer, Other than Underride Guard No Tape* 16 0% 26 1% Not Peeling, Missing 3,698 94% 3,691 96% Peeling, Missing 182 5% 89 2% Unknown 29 1% 53 1% Tape Condition Side No Tape* 54 1% 96 2% Clean 2,570 65% 2,384 62% Some Dirt 1,071 27% 1,164 30% Very Dirty 111 3% 82 2% Unknown 119 3% 133 3% Tape Peeling/Missing Side No Tape* 54 1% 104 3% Not Peeling, Missing 3,664 93% 3,590 93% Peeling, Missing 139 4% 50 1% Unknown 68 2% 115 3% * Trailers has tape in some locations, but not on this component (e.g. tape on side only– no tape on rear or underride guard). 14 There are two small but notable differences between the two states. The percentage of trailers with tape that have some dirt is slightly higher in Pennsylvania than in Florida. In Pennsylvania, more dirt and grime may be splashed up on roads treated with salt or other chemicals to reduce snow, slush and ice on the roads during the winter. The other difference is the percentage of trailers with peeling or missing tape. The percentages are slightly lower in Pennsylvania than Florida. It is unknown why this happened. It is possible that combination trucks in Pennsylvania travel further between loading/unloading, thus reducing the chances that the tape will be damaged. It is also possible that Pennsylvania has more recently retrofitted trailers since data collection started and ended six months later in Pennsylvania than Florida. These trailers may not have had enough time to develop any peeling or missing segments. Table 2-5 also shows that peeling or missing segments of tape occur more often on the rear of the trailer than the side, as expected. The rear of the trailer is more susceptible to scraping and damage when the trailer is loaded and unloaded. Eight percent of the trailers in Florida and five percent in Pennsylvania had peeling or missing segments on the rear of the trailer. Only four percent of the trailers with tape in Florida and one percent in Pennsylvania had peeling or missing segments on the side. The tape on the rear other than the underride guard appears to be just as vulnerable as tape on the rear underride guard. Table 2-6 shows the percentage of missing tape on the rear by state for trailers with missing tape. The 100 percent missing at a particular location may represent trailers that never had tape at that particular location but had tape elsewhere on the trailer. The form is not entirely clear and some officers may have misunderstood the information requested. A large proportion of the trailers coded with 100 percent missing tape on the rear underride guard were pre-standard trailers. Seventy percent (50 cases) in Florida and 64 percent (16 cases) in Pennsylvania are pre-standard trailers, which are not required to have tape on the rear underride guard according to the FMCSA retrofit standard. Similar results were found for elsewhere on the rear of the trailer. Seventyeight percent (31 cases) in Florida and 50 percent (6 cases) in Pennsylvania of the trailers coded with 100 percent missing tape are pre-standard trailers. These may be trailers that were partially retrofitted with tape before FMCSA announced its final rule and have not yet added the missing tape to make it compliant. If you only consider the 1 to 99 percent categories, then 55 percent (84/152 = 55 % in Florida and 42/77 = 55% in Pennsylvania) of the trailers with missing tape on the underride guard have 75 percent or more of the tape intact. This amount of tape missing will probably not seriously diminish its conspicuity effectiveness. On the other hand, tape that is missing on more than 25 percent of the guard may reduce the effectiveness of the tape. In this case, 45 percent (68/152 = 45 percent in Florida and 35/77 = 45 percent in Pennsylvania) of the trailers with missing tape on the underride guard have more than 25 percent of the tape missing. Elsewhere on the rear, 46 percent in Florida of the trailers with missing tape and 48 percent in Pennsylvania have 75 percent or more of the tape intact and 54 and 52 percent, respectively, have more than 25 percent of the tape missing. 15 TABLE 2-6 Number and Percent of Trailers with Missing Tape by Percentage of Missing Tape and State Florida Percentage of Missing Tape on Rear Underride Guard 1-25 % 84 35% 26-50% 46 19% 51-75% 10 4% 76-99% 12 5% 100% 71 30% Unknown Percentage 14 6% Percentage of Missing Tape on Rear - Other than Underride Guard 1-25 % 61 34% 26-50% 45 25% 51-75% 13 7% 76-99% 13 7% 100% 40 22% Unknown Percentage 7 4% Pennsylvania 42 20 8 7 25 28 32% 15% 6% 5% 19% 22% 32 25 3 6 12 8 37% 29% 3% 7% 14% 9% Overall, missing tape was not a big problem when this data was collected. Most trailers with tape either had no tape missing at all or they had 75 percent or more of the tape intact on the rear. Less than two percent of the 3,925 (68/3,925 = 1.7 percent) trailers with tape in Florida had tape missing on more than 25 percent of the rear guard. In Pennsylvania, less than a percent (35/3,859 = 0.9 percent) had tape missing on more than 25 percent of the rear guard. The same percentages were found for elsewhere on the rear in each state. However, this could increase as the trailers get older. Table 2-7 shows the percentage of trailers treated by trailer model year. Model year is the best available surrogate for date of manufacture. NHTSA requires all trailers manufactured on and after December 1, 1993 to have tape. Model years 1993 and 1994 are considered transition years because most 1993 and some 1994 trailers were manufactured before December 1, 1993. In this table, model year was decoded from “good” trailer VINs that yielded a valid model year and valid trailer make. As expected, the percentage of trailers with tape is increasing by model year. Most of the poststandard trailers have tape. More than 80 percent of the model year 1994 trailers have tape and more than half of the model year 1993 trailers have tape. Slightly fewer than half of the prestandard trailers have tape. Also as expected, more pre-standard and transition-year trailers have tape in Pennsylvania than in Florida. Pennsylvania’s data collection period was 6 months later than the Florida period and ended on November 30, 1999, eight months after the FMCSA published a retrofit regulation on 16 March 31, 1999. Although the regulation gives motor carriers two years from June 1, 1999 to install the material on trailers manufactured prior to December 1, 1993, it appears that motor carriers were quickly retrofitting their trailers with tape. Table 2-7 also shows a small portion of post-standard trailers do not have tape (5 percent in Florida and 3 percent in Pennsylvania). These could be coding errors but not necessarily. Possible coding errors included miscoding of the tape presence/absence or inaccurate copying of the VIN. On the other hand, some of these trailers may be exempt from the tape requirement. Trailers designed exclusively for living or office space are not required to have conspicuity treatment. Pole trailers, trailers that carry logs, are also exempt. Some of these trailers may have reflex reflectors, instead of tape, an option allowed by the standard. Finally, some of these trailers may be non-compliant, although this is unlikely. Probably some combination of these possibilities or errors in the data account for the post-standard trailers that do not have tape. TABLE 2-7 Trailer Treatment by Trailer Model Year and State Model Year Decoded from Good VINs Pre-Standard Transition Year Transition Year < MY 1993 MY 1993 MY 1994 Florida Tape No Tape Unknown Pennsylvania Tape No Tape Unknown Post-Standard > MY 1994 747 787 13 48% 51% 1% 144 99 1 59% 41% 0% 246 46 1 84% 16% 0% 1,180 66 11 94% 5% 1% 540 540 12 49% 49% 1% 113 56 2 66% 33% 1% 261 29 2 89% 10% 1% 1,255 43 19 95% 3% 1% Table 2-8 shows some of the crash characteristics of combination truck crashes. Most of the crashes occur on a weekday, when the weather is clear, and involve two or more vehicles. More than two-thirds of the crashes occur on roads with speed limits of 50 mph or higher. It appears that most of the crashes occur on roadways with limited access. In Pennsylvania, 67 percent occur on limited access roadways and in Florida the exact percentage is hard to estimate since most of the interstates and turnpikes and some of the U.S. and State roads have limited access. For the most part, combination trucks are on major roads when they are involved in crashes. There are two minor differences between the crash experience of combination trucks in Florida and Pennsylvania. Pennsylvania has more adverse weather cases than Florida. This is no surprise since the climate is different there. Snow is common in Pennsylvania during the late fall and winter, but rare in Florida. Pennsylvania also has proportionately more single-vehicle crashes than Florida. This disparity is mostly due to reporting differences. Crashes are reported in Florida if 17 there is $500 worth of property damage. In Pennsylvania, crashes are reported if there is at least one vehicle towed from the scene because of damage. Therefore, there are more low-damage, multiple vehicle fender-benders reported in Florida than Pennsylvania. TABLE 2-8 Number and Percent of Crashes by Crash Characteristics and State Florida Pennsylvania Day of Crash Weekday 5,334 88% 4,184 86% Weekend 756 12% 679 14% Unknown 5 0% 1 0% Weather Conditions Clear 5,004 82% 3,416 70% Adverse 973 16% 1,374 28% Unknown 118 2% 74 2% Number of Vehicles 1 864 14% 1,348 28% 2 4,375 72% 2,973 61% 3 or more 856 14% 543 11% Speed Limit 0 to 49 mph 1,743 29% * 1,205 25% 50 - 70 mph 4,187 69% 3,581 74% Unknown 165 3% 78 2% Roadway Access Type Unlimited 1,487 31% Limited 3,245 67% Other/Unknown 132 3% Roadway Type Interstate & Turnpike/Toll 2,461 40% U.S. & State 2,548 42% County & Local 767 13% Other/Unknown 319 5% * Total percentages may not add to 100 percent due to rounding. Table 2-9 compares the driver’s age in the other vehicle involved in combination truck crashes. There is little difference between the driver’s age in Florida and Pennsylvania except for the older drivers. There are slightly more 61-70 year old and 70 and older drivers in Florida than in Pennsylvania. This is not surprising since Florida has an older population. 18 TABLE 2-9 The Driver’s Age in the Other Vehicle Involved in a Crash with Combination Truck by State Florida Driver’s Age 15-20 21-25 26-30 31-50 51-60 61-70 70 + Unknown 303 449 471 1,612 446 304 324 298 7% 11% 11% 38% 11% 7% 8% 7% Pennsylvania 194 332 267 962 288 136 132 193 8% 13% 11% 38% 12% 5% 5% 8% Table 2-10 shows the distribution of driver’s age for passenger vehicles in two vehicle crashes investigated by State police that do not involve combination trucks. This data is from the NHTSA Florida and Pennsylvania State data files. The percentage of 15-20 year old drivers in Table 2-10 is twice that in Table 2-9. Younger drivers are underrepresented as drivers of other vehicles involved in crashes with a combination truck. A possible explanation is that younger drivers, especially 15-18 year old drivers, less frequently encounter combination trucks because their driving habits are different than combination truck drivers. Young drivers drive a lot on local roads to and from school and work. The percentage of all the other age groups is fairly consistent between the two tables. TABLE 2-10 Driver’s Age of Passenger Vehicles Involved in Two-Vehicle Crashes Investigated by State Police that do not Involve a Combination Truck by State Florida Pennsylvania Driver’s Age 15-20 15,387 14% * 5,055 18% 21-25 13,226 12% 3,278 12% 26-30 12,680 12% 2,845 10% 31-50 41,835 39% 9,792 36% 51-60 10,692 10% 2,747 10% 61-70 6,878 6% 1,625 6% 70 + 6,772 6% 1,919 7% Unknown 0 0% 273 1% * Total percentages may not add to 100 percent due to rounding. 19 2.3 CRASHES NOT INVESTIGATED BY STATE POLICE The previous section gave a general overview of the crashes investigated by the FHP and PSP. But the conspicuity data do not include combination truck crashes investigated by local law enforcement agencies, other state agencies, or reported by the drivers themselves. This section is an overview of those crashes. Specifically, this section will address the following: What type of crashes do local law enforcement officers investigate? Are they different from the ones that state law enforcement officers investigate? If they are different, how will these differences influence our effectiveness estimates? The State Police investigate more than half of all the crashes that involve a combination truck. The FHP investigated 59 percent of the combination truck crashes in Florida during 1998. The PSP investigated 60 percent of the crashes in Pennsylvania during 1998. Table 2-11 shows the percent of crashes investigated by the State police and others in Florida and Pennsylvania for various crash characteristics. The FHP and the PSP investigate almost all of combination truck crashes that occur on major roads where they have jurisdiction. The PSP investigate 93 percent of the crashes on limited access roads and the FHP investigate 93 percent on interstates and turnpikes/toll roads. These agencies also investigate more than half of all the crashes for most of the crash characteristics in Table 2-11. They investigate more than half of the weekday, weekend, clear, adverse, daylight, dark, high speed, rural, etc. crashes that involve a combination truck. The conspicuity data underrepresents crashes that occur in urban areas, on county and local roads, or on roadways with lower speed limits. The majority of these crashes are investigated by local police, sheriffs, or other police agencies that have jurisdiction in these areas or are reported by the drivers themselves. The local police agencies investigate somewhere between 64 and 74 percent of the crashes that occur in urban areas, 68 percent on county and local roads, and about 65 percent on roads with speed limits less than 50 miles per hour. There is little difference between what the FHP and PSP investigate in their respective states. The only exceptions appear to be single-vehicle crashes and crashes that occur in urban areas. The PSP investigates 74 percent of the single-vehicle crashes that involve a combination truck, while the FHP investigates only 60 percent of these crashes. The local agencies in Florida also investigate more crashes that occur in urban areas than their counterparts in Pennsylvania. The reporting threshold differences between these states probably account for these discrepancies. A crash in Florida is investigated if it involved at least $500 worth of damage. In Pennsylvania, a crash is investigated if at least one of the vehicles is towed away. Therefore, local police agencies in Florida will investigate more low-speed, single-vehicle crashes or low-speed crashes in urban areas than the local police agencies in Pennsylvania. The fact that a proportion of crashes are not investigated by the State police will not significantly affect our effectiveness estimates. In Chapter 4, we will see no consistent difference in the effectiveness in rural vs. urban areas or on low vs. high speed limit roads, so the state police effectiveness estimates are also appropriate for the groups of crashes investigated by other 20 agencies. When we complete benefits in Chapter 5, we will include non-state police investigated crashes in the “size of the problem” estimate, so as not to underestimate the benefits. TABLE 2-11 Percent of Crashes Reported by Enforcement Agency and State Florida Pennsylvania Day of Crash FHP Other PSP Other Weekday 58% 42% 59% 41% Weekend 64% 36% 72% 28% Weather Conditions Clear 56% 44% 58% 42% Adverse 65% 35% 67% 33% Number of Vehicles 1 60% 40% 74% 26% 2 57% 43% 55% 44% 3 or more 67% 33% 57% 43% Speed Limit 0 to 49 mph 35% 65% 34% 66% 50 to 70 mph 89% 11% 84% 16% Roadway Access Type Unlimited 55% 45% Limited 93% 7% Other/Unknown 61% 39% Roadway Type Interstate & Turnpike/Toll 93% 6% U.S. & State 63% 37% County & Local 31% 68% Other/Unknown 19% 81% Light Condition Daylight 57% 43% 55% 45% Dark Conditions 64% 36% 70% 30% Rural/Urban Rural 77% 23% 83% 17% Urban 26% 74% 36% 64% 21 22 CHAPTER 3 BASIC ANALYSIS Tractor-trailer combinations in which trailers are equipped with retroreflective tape ought to experience a reduction of side and rear impacts into the trailer by other vehicles in dark conditions - relative to the number that would have been expected if the trailers had not been equipped. The analytic challenge is to compute the “expected” number of impacts and quantify the reduction. The critical parameters are: (1) whether or not the trailer is tape-equipped; (2) the light condition - dark (comprising “dark-not-lighted,” “dark-lighted,” “dawn” and “dusk”) vs. daylight; and (3) relevant vs. non-relevant crash involvements. Relevant crash involvements are those where another vehicle crashed into the side or rear of a heavy trailer, because the tape can help the other driver see and possibly avoid hitting the trailer. The non-relevant group consists of single-vehicle crashes of tractor-trailers (where visibility of the tractor-trailer to other road users is not an issue at all) and impacts of the front of the tractor into other vehicles (where conspicuity of the side and rear of the trailer is also not an issue). Each of these parameters defines a sort of control group. The vehicles without tape are a control group that can be compared to the vehicles equipped with tape. Since the tape ought to have substantially less effect (if any) by daylight than in dark conditions, daylight crashes are a control group relative to crashes in the dark. The most satisfactory definition of the “expected” number of side/rear impacts in the dark uses all three of these control groups. 3.1 DEFINITIONS The data base for this analysis is a vehicle-oriented file, with one record for each tractor-trailer combination that was involved in a crash. Initially, Florida and Pennsylvania data will be analyzed separately. The Florida file includes 6,444 tractor-trailer combinations and the Pennsylvania file includes 5,349. The critical parameters that must be defined for this analysis are tractor-trailer combinations, trailer treatment, light conditions and crash mode/point of impact. Some of the parameters can be defined from data elements on the NHTSA Green and some from data elements the state PAR. The definitions for the parameters that are defined from elements on the NHTSA Green are the same in Florida and Pennsylvania. But each state has it own unique way of coding elements on its PAR, so the definitions for parameters that are defined from elements on the state PAR cannot be exactly the same. For these parameters, the definitions ought to be made as similar as possible. The States also differ in the exposure and crash characteristics of combination trucks. Below are the definitions and the differences found in the conspicuity data for these critical parameters. First, it is necessary to define “tractor-trailers.” The vehicle type and number of trailers were used to identify heavy trucks pulling at least one trailer. “Vehicle type” is a data element on the state PAR and identifies the body style of a vehicle. “Number of trailers” is on the NHTSA Green form 23 and identifies the number of trailers that were attached to a vehicle. (Small trailers typically pulled by light vehicles are not included in the analysis.) Tractor-trailer combinations were defined as follows: State Definition Florida Pennsylvania veh_type = 4, 5, 6, 77 and trlno = 1, 2 body_type=70, 73, 74, 75, 76, 77, 79 and trlno = 1, 2 The trailer treatment8 (the presence or lack of retroreflective tape) is easily identified by a variable collected on the NHTSA Green. If the truck tractor was pulling only one trailer and the trailer had tape, then the combination truck was classified as treated. If the trailer had no tape, then the combination truck was classified as untreated. Few tandem trailers were found in the conspicuity data although both Florida and Pennsylvania allow heavy trucks to pull up to 2 trailers. In these cases, the presence or lack of tape was defined for both trailers. If both trailers had tape, then it was classified as treated and if both trailers did not have tape, then it was classified as untreated. A truck pulling two trailers where one trailer had tape and the other one did not were classified as unknown, as are combinations with unknown tape conditions on a single trailer or at least one of the tandem trailers. Table 2-3 shows that fewer than 5 percent of the combination trucks are pulling two trailers and very few cases were classified as unknown because the tape was inconsistent on the two trailers. Table 3-1 shows that 60 percent of truck trailer combination trucks have tape in Florida and 70 percent have tape in Pennsylvania. Combination trucks with “unknown” trailer treatment were excluded from the analyses. TABLE 3-1 Retroreflective Tape by State for Tractor-Trailer Combinations Florida Pennsylvania Total Treated 3,880 60% 3,751 70% 7,631 Untreated 2,443 38% 1,283 24% 3,726 Unknown 121 2% 315 6% 436 Total Vehicles 6,444 5,349 11,793 The light conditions at the time of the crash were classified into “dark” and “daylight” conditions for the analysis using a variable on the NHTSA Green. Table 3-2 shows the different levels of light conditions along with the number and percentage of these cases. Note the difference in the 8 Conspicuity treatment of truck tractors is arguably a neutral factor in evaluating the effectiveness of the treatment in preventing crashes involving truck tractor-trailer combinations. There is no side treatment applied to truck tractors, while the rear treatment is masked by the trailer being towed. 24 percentage of daylight and “dark-not-lighted” conditions between Florida and Pennsylvania. Although there is no exposure data to support this premise, this suggests that combination trucks are driven more often at nighttime in Pennsylvania than in Florida. TABLE 3-2 Light Conditions by State for Tractor-Trailer Combinations Florida Pennsylvania Daylight 4,408 68% 3,139 59% Dark-Not-Lighted 1,245 19% 1,628 30% Dark-Lighted 505 8% 334 6% Dawn 179 3% 147 3% Dusk 91 1% 86 2% Unknown 16 0% 15 0% Total Vehicles 6,444 5,349 Total 7,547 2,873 839 326 177 31 11,793 The basic analysis compares dark conditions to daylight conditions. “Dark” conditions include “dark-not-lighted,” “dark-lighted,” “dawn,” and “dusk.” Other analyses will compare dark-notlighted to daylight; and dark-lighted, dawn, and dusk to daylight. Cases with unknown light conditions are excluded from the analysis. Crash mode/point of impact were used to identify single-vehicle cases and frontal, side, and rear initial impacts. Single-vehicle cases were identified first, regardless of their initial point of impact. A single-vehicle case involves only a tracto