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Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes (2010)

Chapter: Chapter 5 - Long-Term Data Collection Plan

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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
×
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
×
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
×
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
×
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
×
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Suggested Citation:"Chapter 5 - Long-Term Data Collection Plan." National Academies of Sciences, Engineering, and Medicine. 2010. Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes. Washington, DC: The National Academies Press. doi: 10.17226/14448.
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55 5.1 General The primary goal of the current study is to identify the dis- tribution of impact conditions—including speed, angle, and vehicle orientation—of serious injury and fatal ran-off-road crashes. However, there remain many other questions and issues that need to be addressed, some of which are as follows: 1. Identify distributions of impact conditions—including speed, angle, and vehicle orientation—as a function of highway functional class. These data would provide inputs for benefit/cost (B/C) analysis codes and development of hardware performance-level selection guidelines. 2. Develop a link between occupant compartment deforma- tion and occupant risk in ran-off-road crashes. These data would be helpful in establishing intrusion limits for crash testing guidelines. The magnitude and location of intrusion would need to be identified in order to establish reasonable limits. 3. Quantify the occupant risk associated with partial rollovers by vehicle class. Large trucks are allowed to roll 90 degrees during a crash test, but the test is deemed a failure if a small car or a light truck rolls 90 degrees. Data correlating degree of rollover with occupant injury would be helpful. 4. Establish a link between impact conditions and probability of injury for common safety features and roadside hazards. These data would provide a link between crash conditions and accident severity that would be invaluable in refining B/C analysis techniques. 5. Identify distribution of all vehicle trajectories. These data could be used to incorporate curvilinear paths into the Roadside Safety Analysis Program (RSAP) and to develop guardrail length-of-need calculation procedures. 6. Identify the effects of roadside slopes on vehicle trajectories. This information would contribute to the refinement of B/C analysis tools and the development of length-of-need calculations. 7. Identify the relationship between impact angle and crash severity for longitudinal barriers. These data would con- tribute to the refinement of B/C analysis tools that in turn would be useful in identifying optimum flare rates for longitudinal barriers. 8. Identify the effects of curbs, ditches, and other terrain irregularities placed in front of safety hardware on the pro- bability of injury during a crash. This list of questions and issues is by no means exhaustive, but it serves to illustrate the many unanswered questions that can be addressed with in-depth crash data. The database cre- ated from the current study may provide answers to some of these questions, but the sample size and the level of detail would limit its applications. There remains a need for a long- term effort to collect in-depth data on single-vehicle, ran-off- road crashes in a continuous and systematic manner. This long-term data collection effort will require a sponsor- ing agency with continuing funding sources. The sponsoring agency would ideally be national in scope and have sufficient resources to provide the needed funding on a long-term basis. One possible sponsoring agency is the FHWA. However, given the situation with the research budget in recent years, it is unlikely that the FHWA will sponsor such a long-term data collection effort. Another alternative is to establish a multi- state pooled fund study, similar to the Mid-States Pooled Fund Program administered by the Nebraska Department of Roads. While this is a viable approach, the required funding per year and the commitment for a long-term effort may be too much for individual states to handle. The most logical choice is for AASHTO to sponsor the effort and the program to be administered through NCHRP. There is no question that AASHTO and NCHRP have the required organization and resources to carry out this long- term data collection effort. For example, this current study was requested by the AASHTO Technical Committee on Roadside Safety (TCRS) and administered through NCHRP. C H A P T E R 5 Long-Term Data Collection Plan

56 This chapter outlines a proposed plan for such a long-term data collection effort. Unlike the work plan for the current study, this proposed long-term data collection plan is more at the conceptual level. If and when this proposed plan is adopted for implementation, it will then be necessary to develop a more detailed data collection plan. 5.2 Data Collection Alternatives As discussed previously, there were three basic alternatives for the data collection effort in the current study: 1. New data collection system 2. Prospective special study under the NASS CDS program 3. Retrospective supplemental data collection for existing NASS CDS cases The retrospective approach is too limited in terms of data items that can be collected and in flexibility. Some of the desired data elements are perishable, i.e., lost after a period of time. For example, data on the struck object would be lost after repair of the object. This information could be necessary to assess the pre-impact characteristics and conditions of the object as well as to determine its impact performance. The sampling scheme is dictated by the CDS since only sample cases within it are avail- able. For certain types of crashes, a very long time would be required before the sample size becomes sufficiently large for proper analysis. Furthermore, NHTSA changed its policy in 2003 so that police accident reports are no longer a part of the final NASS case. Police reports are maintained at the Zone Cen- ters for only one year to allow for quality control procedures. This change in policy will, in essence, eliminate the use of the retrospective approach. The establishment of a new data collection system is a viable, but expensive approach. As discussed previously, there will be an initial setup cost for the data collection teams, such as hiring of new personnel, establishing and furnishing the offices, pur- chasing the necessary equipment for conduct of crash investi- gation, etc. The investigators will then have to be trained extensively in the basics of in-depth level crash investigation, including both classroom and on-the-job training. Then, there is the need to establish cooperation with the local agencies, such as law enforcement agencies for the notification system, vehicle towing and repair facilities for access to the involved vehicles, hospitals and clinics for medical records/information on injury severity, and transportation agencies for highway-related infor- mation. It is also necessary to establish quality control proce- dures to assure that the data collection effort is conducted properly in terms of validity and accuracy. The most efficient and economical approach is to make use of the existing NASS data collection system. First, the initial setup cost will be greatly reduced since the NASS data teams are already in place. Depending on the nature of the data collection, new investigators may have to be hired and trained and there may be requirements for additional office space and equipment. However, the setup costs should be only a fraction of the cost required to establish a new data collection system. Second, with supplemental field data collection, the portion of the CDS cases involving single-vehicle, ran-off-road crashes will be available for use at a relatively low cost. Third, under the NASS special study subsystem, cases may be selected outside of the CDS sam- ple to address specific types of crashes under study. The proposed long-term data collection plan is, therefore, built around the NASS CDS data collection system, including both within-sample supplemental data collection and outside- sample special studies. Note that while NHTSA has maintained the philosophy of allowing the NASS infrastructure to be used for other data collection needs, there are requirements that the special study: • Should not have an adverse affect on normal NASS operations • Should not reduce the current NASS CDS caseload for researchers • Should not have any impact on current CDS data collec- tion procedures and data elements being collected • Should not have any impact on NASS operational costs • Must cover all costs associated with the development and operation of the study • Should be within the interests and expertise of the National Center for Statistics and Analysis (NCSA) • Must conform with NHTSA privacy guidelines regarding collected data • Must use existing NASS contractors for all data collection and quality control operations • Should use a feasibility study to appraise the likely impact and success of the study • Should use a pilot study in the development of formalized procedures • Should present to NHTSA an analysis plan, i.e., what re- search questions are to be answered These considerations are addressed in the development of the proposed data collection plan presented in the following section. 5.3 Proposed Data Collection Plan The proposed data collection plan would have two major subsystems, both of which would be prospective in nature (i.e., the cases would be sampled from new crashes): 1. Continuous sampling subsystem within the CDS sample, and 2. Special study subsystem outside the CDS sample.

57 The continuous sampling subsystem is intended for a general database to address items of interest pertaining to single-vehicle, ran-off-road crashes. This general database would be similar to the database developed under this study. This continuous sampling subsystem would consist of selecting eligible cases from within the CDS sample and supplementing the basic CDS data with additional field data on roadway, roadside, and struck-object characteris- tics. In addition, the cases would be reconstructed to the extent possible to estimate impact conditions and vehicle trajectories. The special study subsystem would be ad hoc in nature, intended to address specific questions or roadside safety features. For example, a special study may be designed to assess the impact performance of guardrail terminals. In order to assure a sufficient sample size to properly assess the field impact performance, the special study may have to select cases from outside as well as within the CDS sample. In addition to the basic CDS data and the supplemental field data on roadway and roadside characteristics, detailed information would be collected on the safety device of interest. Again, the cases would be reconstructed to the extent possible to estimate impact conditions and vehicle trajectories. More detailed descriptions of these two subsystems are presented in the following sections. 5.3.1 Continuous Sampling Subsystem As mentioned above, the continuous sampling subsystem is intended for a general database on single-vehicle, ran-off- road crashes. The cases would be selected from within the NASS CDS sample using sampling criteria similar to those used with the retrospective approach in the current study, i.e., • Area type—rural and suburban • Single-vehicle, ran-off-road crashes • Passenger-type vehicles only—passenger cars and light trucks • Speed limit ≥ 75 km/h (45 mph) The sampling criteria may be modified periodically to change the range of eligible cases. For example, the area type may be expanded to include urban areas with speed limits of 65 km/h (40 mph) and slower, or the vehicle type may be expanded to include single-unit trucks and tractor-trailers, depending on the questions to be addressed with the data. Also, since the cases would be selected within the CDS sample, the notification system would be the same as the CDS. The basic data elements collected under NASS CDS are very extensive in areas pertaining to the vehicle and occupants, but are lacking in detail in the areas of: 1. Roadway and traffic characteristics 2. Roadside characteristics 3. Struck-object characteristics For the type of questions that are of interest to the roadside safety community, information on the roadway, traffic, road- side, and struck-object characteristics would be needed for the analyses. Thus, it would be necessary to collect supplemental field data on these data elements. Some of the supplemental data, such as highway type, functional class, and traffic charac- teristics, would be obtained from the local or state transporta- tion agencies, and cooperation would need to be established with these agencies. Note that even with the supplemental data collection, the level of detail on struck-object characteristics would still be lim- ited. First, there are simply too many roadside features to include in the data collection protocol for any details to be col- lected on a particular roadside feature. Second, given the intent of a general database on single-vehicle, ran-off-road crashes, overly detailed information on struck objects would be overkill. Furthermore, it would be very difficult and costly to train the investigators on the details of all these roadside features. The special study subsystem is the more appropriate vehicle for col- lecting detailed information on selected roadside features. It is anticipated that the supplemental field data elements for the continuous sampling subsystem would be similar to those used in the current study, with perhaps a few more data ele- ments and additional photographs. It is also anticipated that there would be additional coding on information pertaining to impact conditions and vehicle trajectories based on the basic CDS data, scaled diagram, and supplemental field data. Finally, the cases would be reconstructed to estimate the impact speeds. One key consideration is how the supplemental field data would be collected. There are basically two approaches for the data collection: • Existing NASS investigators • Newly hired and specially trained investigators For the continuous sampling subsystem, the use of existing NASS investigators would be the more logical and cost-effective means of collecting supplemental field data. Based on previous experience with the retrospective studies, the additional time required to collect and code the supplemental field data is esti- mated to be no more than two hours per case. For a given Primary Sampling Unit (PSU), the number of eligible cases is likely to be less than 50 per year. Thus, the additional time devoted to the supplemental data collection would not be more than 100 hours per year per PSU, or less than two hours per week per PSU. It is evident from the estimated workload that it would not be cost effective to hire an additional investigator per participating PSU for this supplemental field data collection.

58 On the other hand, if the special study subsystem is imple- mented with the continuous sampling subsystem, then one new investigator per participating PSU would make immi- nent sense. This additional investigator would be responsible for collecting both the supplemental data on the continuous sampling cases as well as the special study cases, although the majority of the investigator’s time would be devoted to special study cases. 5.3.2 Special Study Subsystem The general database developed under the continuous sam- pling subsystem will be invaluable to addressing general trends and questions on single-vehicle, ran-off-road crashes. How- ever, it lacks the detail and sample size to address specific ques- tions, such as the impact performance of guardrail terminals. As discussed previously, the level of detail on struck-object characteristics will be limited for the supplemental data col- lected under the continuous sampling subsystem. Also, the number of cases involving a specific roadside feature will be relatively small since the cases are sampled within the CDS sample and it will likely take a very long time before a suffi- cient sample size becomes available. The special study subsystem is designed to handle these ad hoc studies. In contrast to the continuous sampling subsys- tem, a special study is tailored to a specific roadside feature. Thus, the data elements, particularly those pertaining to the roadside feature, can be designed to the desired level of detail. Also, the sampling of the cases would be outside of the CDS sample, thus assuring a sufficient sample size within a reason- able period of time. As mentioned previously, a new investigator would be hired specifically for the data collection effort at each partic- ipating PSU. The investigator would first receive training similar to that of a NASS investigator so that the investigator can collect the basic data elements for a CDS case. In addi- tion, the investigator would receive special training to collect and code the new data elements for the continuous sampling subsystem and the special study being conducted. 5.3.3 Quality Control Two Zone Centers currently provide the quality control and oversight of the PSUs in the CDS data collection effort. It is envisioned that the Zone Centers would serve the same role in the continuous sampling subsystem and the special study subsystem. One question is whether the additional coding on informa- tion pertaining to impact conditions and vehicle trajectories should be handled at the PSU level by the designated investiga- tors or by Zone Center personnel. Either approach is workable, but it may be more appropriate for the Zone Center personnel to handle this task. First, the task requires considerable expert- ise and experience, which may be beyond the capability of the PSU investigators, particularly the new hires with little or no experience. Second, the work would likely be more accurate and consistent if handled by Zone Center personnel. Third, one or more new persons can be hired at each of the two Zone Centers specifically for this task of quality control and coding of the additional information. This would minimize the con- cern of adversely impacting the CDS operation. 5.3.4 Project Management It is envisioned that an outside contractor would be hired by the sponsoring agency to coordinate with NASS on the data collection effort. The key responsibilities for this con- tractor would include, but not be limited to: • Design of the data collection protocol for both the contin- uous sampling subsystem and the special study subsystem • Reconstruction of the cases to estimate the impact speeds and conditions • A second level of quality control of the supplemental data collected • Maintenance of the general database and special study database • Analysis of the data to address specific questions A project panel or a technical advisory committee, com- posed of management-level personnel from the sponsoring agency and NASS, would oversee the overall conduct of the study. The panel would provide guidance and direction to the contractor and review the study progress and results. 5.4 Pilot Study A pilot study was conducted to demonstrate the feasibility of such a long-term data collection effort to both the poten- tial sponsor and to NHTSA. Specifically, the objectives of this pilot study were to: • Demonstrate the feasibility of integrating this long-term data collection effort on ran-off-road crashes into the reg- ular NASS CDS program. • Identify and resolve any potential problems associated with this long-term data collection effort. • Estimate time and manpower requirements associated with this long-term data collection effort. 5.4.1 Scope The pilot study covered only the continuous sampling sub- system within the CDS sample. The feasibility and costs of the

59 special study subsystem outside of the CDS sample would vary greatly depending upon the specific nature of the study to be undertaken. Therefore, evaluation of the special study subsystem is beyond the scope of the current study. The scope of the pilot study involved the conduct of a supplemental data collection effort at a small number of PSUs for a limited period of time. The same data collection protocol used for the current retrospective study was employed for this pilot study for the sake of simplicity. This eliminated the need to develop a new data collection protocol and to retrain the PSU researchers and Zone Center (ZC) personnel. It should be pointed out that the integrated supplemental field data collection and reconstruction effort are actually eas- ier and more efficient than the current retrospective study: • No wasted effort to re-familiarize the researchers and ZC personnel with details of the old cases. • No additional time to travel and locate the crash site. • Scene evidence (e.g., damage to roadside hardware) avail- able for documentation. • ZC staff can perform the reconstruction in conjunction with their regular quality control effort in less time and with greater accuracy. More detailed descriptions of the pilot study are presented in the next section, followed by results of the study and con- clusions and recommendations. 5.4.2 Data Collection Protocol As mentioned previously, the same data collection proto- col used for the current retrospective study was employed for the pilot study with minor modifications. Highlights of the data collection protocol are summarized as follows. Based on the frequency of single-vehicle, ran-off-road crashes and availability of trained researchers, two PSUs were selected for participation in the pilot study: PSU 48 and PSU 78. The time period for the pilot study was the nine weeks from October 4, 2004, to December 4, 2004. The cases were selected from within the CDS sample, i.e., from cases that were already included in the CDS sample. The sampling criteria were the same as the current supplemental data collection effort except for the completion requirement, i.e., single-vehicle, ran-off-road crashes on roadways with speed limit greater than or equal to 45 mph. In order to avoid disruptions to the regular CDS data collection effort, each researcher was limited to no more than one case per week. However, all eligible cases were documented for the report. Thus, the maximum expected number of eligible cases was limited to four per week, two cases per week from each PSU. The same data collection forms and procedures as the cur- rent effort were used for the pilot study, including: • Supplemental Data Collection Form • Object Struck Data Collection Form • Reconstruction Coding Form • Scene photographs A log form was developed to identify each case and its status (i.e., active or not active); track the additional time spent on the supplemental field data collection at the PSU level and on qual- ity control and reconstruction at the ZC level; and document any problems and provide comments. No training for the PSU researchers or ZC personnel was deemed necessary since they were already familiar with the data collection protocol. The supplemental data collection forms and reconstruction coding forms were completed and submitted in hard copies. The CDS data elements of the selected cases were obtained from preliminary approved cases posted on the NHTSA web- site with a time lag of approximately six to eight weeks. 5.4.3 Pilot Study Results As shown in Table 90, there were a total of 22 eligible cases during the nine-week study period, 16 cases for PSU 48 and 6 cases for PSU 78. Of these 22 eligible cases, 16 cases (72.7%) were actually sampled, 11 cases (68.8%) for PSU 48 and 5 cases (83.3%) for PSU 78. For each sampled case, the PSU and Zone Center personnel were asked to complete a log form, documenting the time required to collect, process, and quality control the additional field data and to reconstruct the cases except for impact speed, including: • PSU – Field time to collect the additional data – Office time to process the additional data • Zone Center – Time to quality control the additional data – Time to reconstruct the impact conditions other than impact speed Note that these times pertain to only the additional data elements and not the time required for the NASS CDS data collection effort. In addition, the researchers were asked to note any problems or unusual events encountered in the field or office on the log form. Table 91 summarizes the additional time required for each of these 16 sampled cases and their averages. As may be expected, the additional time varies greatly on a case-by-case basis, depending on the complexity of the crash and, to some extent, the efficacy and expertise of the individual investiga- tors. Overall, the time required for the additional work on the supplemental data collection ranges from 60 to 255 minutes per case with an average of 135.3 minutes per case.

60 No. of Eligible Cases No. of Sampled Cases Week Beginning PSU 48 PSU 78 Total PSU 48 PSU 78 Total October 4 0 2 2 0 1 1 October 11 4 0 4 2 0 2 October 18 2 1 3 1 1 2 October 25 1 0 1 1 0 1 November 1 4 1 5 2 1 3 November 8 2 1 3 2 1 3 November 15 1 0 1 1 0 1 November 22 1 0 1 1 0 1 November 29 1 1 2 1 1 2 Total 16 6 22 11 5 16 Table 90. Number of eligible and sampled cases. Additional Time Required (Minutes) PSU Zone Center Case Number Field Office QualityControl Recon- struction Total 04-48-235J 60 20 10 40 130 04-48-238K 30 45 5 25 105 04-48-246D 20 30 5 35 90 04-48-253H 60 120 5 35 220 04-48-254B 50 50 5 10 115 04-48-259K 30 20 5 15 70 04-48-262C 20 20 10 30 80 04-48-265K 40 40 10 20 110 04-48-267J 60 20 10 50 140 04-48-274J 25 5 5 25 60 04-48-280K 60 120 10 65 255 PSU 48 Average 41.4 44.6 7.3 31.8 125.0 04-78-134D 60 60 10 35 165 04-78-140K 120 0 10 35 165 04-78-143K 90 60 10 20 180 04-78-144J 60 60 10 30 160 04-78-148K 60 0 10 50 120 PSU 78 Average 78.0 36.0 10.0 34.0 158.0 Combined Average 52.8 41.9 8.1 32.5 135.3 Table 91. Additional time required.

61 At the PSU level, the additional field time for collection of the supplemental data ranges from 20 to 120 minutes with an average of 52.8 minutes. The processing time in the office ranges from 0 to 120 minutes with an average of 41.9 minutes. The combined field and office time at the PSU level ranges from 30 to 180 minutes with an average of 94.7 minutes. At the Zone Center level, the additional time for quality control of the supplemental data ranges from 5 to 10 minutes with an average of 8.1 minutes. The time needed to reconstruct the impact conditions (except for impact speeds) ranges from 15 to 65 minutes with an average of 32.5 minutes. The com- bined time at the Zone Center level ranges from 15 to 75 min- utes with an average of 40.6 minutes. The researchers were asked to report any problems or unusual events encountered during different phases of this supplemental data collection effort for this pilot study. To ensure completeness, the researchers were asked to enter “None” if there are no problems or comments. The comments are tabulated in Table 92. Overall, there are no major com- ments of concern. Some of the comments pertain to common operational issues, such as scene evidence, photography, and interference from traffic and Visio printer setup, which are not specifically related to the supplemental data collection. Other comments pertained to definitions and procedural issues that can be easily remedied with some training, including: • Multiple impacts • Impacts with more than one object in close proximity • Reference framework for lateral distance measurements of trajectory Case No. PSU Comments Zone Center Comments 04-48-235J I had to go back to the scene and redo my lateral measurements because I forgot to separate the rollover initiation, but that was the researcher’s fault. Other than that, no problems. Visio printer setup. Had to “grab” missing images from case. 04-48-238K None. Visio printer setup. 04-48-246D None. Had to create an object form for 2nd object struck. Visio printer setup. 04-48-253H Two utility poles situated close beside each other were struck and coded as one event. Visio printer setup. 2 extra object forms added for Events 2 and 3. 04-48-254B Another crash occurred in same area / deciphering evidence. In-house Visio issue. 04-48-259K None. In-house Visio issue. 04-48-262C Difficult to place ID card in images on scene due to Interstate traffic. Reconstruction – changed angle of departure off barrier, so re-calculated FRP. (No scene evidence at FRP.) 04-48-265K Vehicle departed right road edge and returned to road to rollover. Slope measurements taken at road departure. None. 04-48-267J None. Visio did not migrate properly. Had to create from printout copy. 04-48-274J None. Visio printer software issues. 04-48-280K Multiple events and scene evidence being contaminated made it difficult to determine impacts and locations. Same Visio printer setup problem. Listed 3 events (that affected CG) only (not 6). Laterals on a curve were changed to be perpendicular to the curved road edge. 04-78-134D None. Had to annotate POD, etc. on Visio. Advised researcher how to do that “next time”. 04-78-140K Had a hard time placing the cones in a straight line from road edge to final rest. 12 laterals taken from POD to FRP, not POD to POI. Had to re-calculate these from Visio. 04-78-143K Heavy rain and it caused delays in getting out to take images. None. 04-78-144J None. Researcher took 12 laterals from POD to FRP. Re-computed 6 laterals from POD to POI. 04-78-148K Researcher unsure how to fill in the reconstruction form for events 2 and 3. Filled in subsequent reconstruction form for researcher. Table 92. Summary of comments.

62 5.4.4 Summary of Findings and Recommendations The following is a summary of findings and recommenda- tions gleaned from the pilot study: • The study clearly demonstrated the feasibility of incorpo- rating a long-term data collection effort on ran-off-road crashes into the existing NASS CDS program. However, note that the study included only the continuous data col- lection subsystem. Thus, the study results would not apply to the special study subsystem. • It took an average of 135 minutes per case for the supple- mental data collection effort, consisting of 95 minutes at the PSU level and 40 minutes at the Zone Center level. Furthermore, it is reasonable to expect that the time would decrease slightly once the researchers are trained and become familiar with the data elements and procedures. • There were no major issues of concern regarding the data collection or reconstruction of the cases. 5.5 Data Collection Protocol— Continuous Sampling Subsystem The data collection protocol for the proposed continuous sampling subsystem is essentially unchanged from that of the current retrospective study or the pilot study. Detailed descriptions of the data collection protocol are provided pre- viously in Chapter 1 and Section 5.4 and will not be repeated herein. Only the highlights of the data collection protocol are summarized in this section. 5.5.1 Sampling Plan The cases for the continuous sampling subsystem would be selected from within the NASS CDS sample, using the same notification system. The sampling criteria may include, but are not limited to, the following: • Area type—rural and suburban • Single-vehicle, ran-off-road crashes • Passenger-type vehicles only—passenger cars and light trucks • Speed limit ≥ 75 km/h (45 mph) The actual sampling criteria used may vary, depending on the specific questions to be addressed with the data. For example, the area type may be expanded to include urban areas with speed limits of 65 km/h (40 mph) and slower, or the vehicle type may be expanded to include single-unit trucks and tractor-trailers, depending on the questions to be addressed in the study. On the other hand, the actual sample size and the PSUs to be included in the data collection effort is merely a question of available funding. 5.5.2 Data Collection Forms The proposed data collection forms and procedures for the continuous sampling subsystem are similar to those used in the current effort and the pilot study, but with some enhance- ments based on experience gained in this study, including: • Supplemental Highway Data Collection Form • Object Struck Data Collection Form: – Barrier – Crash Cushion – Embankment – Pole Support – Tree – Other Struck Object • Reconstruction Coding Form: – First Harmful Event – Subsequent Harmful Event • Performance Assessment Form • Scene Photographs Copies of these proposed data collection forms and the cor- responding coding and field procedures manuals are included in Appendix F. 5.5.3 Organization The data collection effort is best sponsored by AASHTO and administered through NCHRP. An outside contractor would be hired to conduct the study and to coordinate the data collection effort with NASS. A project panel, or a tech- nical advisory committee composed of management-level personnel from the sponsoring agency and NASS, would oversee the overall conduct of the study, provide guidance and direction to the contractor, and review the study progress and results. If only the continuous sampling subsystem is to be imple- mented, then the most logical and cost-effective arrangement is for the field data to be collected by existing NASS inves- tigators and quality controlled by Zone Center personnel, assuming the additional work load would not adversely affect the regular CDS operation. Based on previous experience with the retrospective studies, the additional time required to collect and code the supplemental field data is estimated to be no more than two hours per case. For a given PSU, the num- ber of eligible cases is likely to be less than 50 per year. Thus, the additional time devoted to the supplemental data collec- tion would not be more than 100 hours per year per PSU, or less than two hours per week per PSU. It is evident from the

63 estimated workload that it would not be cost-effective to hire an additional investigator per participating PSU for this sup- plemental field data collection. Coding of additional information and reconstruction of the cases as well as the performance assessment would be handled by the outside contractor so as to minimize the time required of the PSU and Zone Center personnel. 5.6 Data Collection Protocol— Special Studies Subsystem Under the special study subsystem, single-vehicle, ran-off- road crashes involving specific roadside safety features or devices would be selected from both within and outside the CDS sample. The data to be collected under this special study subsystem would include: 1. Selected CDS data 2. Supplemental highway data for the continuous sampling subsystem 3. Detailed information on the roadside feature or device under study The special study cases would then be reconstructed to estimate impact conditions and vehicle trajectories, and the impact performance of the specific roadside feature/device under study will be assessed. The specific data collection protocol will differ from spe- cial study to special study. Thus, the discussions will be more general in nature to cover the key considerations. 5.6.1 Sampling Plan As mentioned previously, it is impossible to devise a spe- cific sampling plan that works for all special studies. Thus, the discussions will be more general in nature to cover the key considerations in developing the sampling plan. Sample Size. The number of cases to be investigated would first have to be determined. This is usually determined by study/analysis requirements and the available funding. Study Location. PSUs with the most eligible cases would first be identified. The most appropriate PSUs would be selected for participation in the special study, based on the required sample size and factors such as: number of eligible crashes, the number and experience of the investigators, geo- graphical location, work load, etc. It is critical that the PSUs are selected in conjunction with NHTSA and the two Zone Centers. Every effort should be made to avoid interference with the regular NASS CDS work of the selected PSUs. Study Period. Again, this is a function of the required sample size and the number of eligible cases from the partic- ipating PSUs. Sampling Plan. The special study subsystem would typically select cases from both within and outside the NASS CDS sam- ple. The sampling plan should take into account key consider- ations as those for the selection of PSUs including number of eligible crashes, the number and experience of the investigators, geographical location, work load, etc. Again, it is critical to develop the sampling plan in conjunction with NHTSA and the two Zone Centers. Every effort should be made to avoid inter- ference with the regular NASS CDS work of the selected PSUs. Notification System. A special notification system is needed for cases to be selected from outside the NASS CDS sample. Care should be taken to make sure that the notification sys- tem for the special study would not interfere with the CDS or add too much work to the cooperating agencies. Depending on the nature of the special study, another consideration is the time lag from the time the crash occurred to the time the PSU is notified of the crash. For certain types of crashes, the time lag may need to be relatively short in order to gather the needed scene evidence. In such cases, the notification system would have to be devised to reduce the time lag to an accept- able level. 5.6.2 Data Collection Forms The general structure of the data collection forms and pro- cedures for the special study subsystem would be similar to those used with the continuous sampling subsystem, includ- ing but not limited to: • Supplemental Highway Data Collection Form • Object Struck Data Collection Form • Reconstruction Coding Form • Performance Assessment Form • Scene Photographs However, the forms would be tailored to the specific road- side feature/object under study. The Supplemental Highway Data Collection Form would likely remain mostly unchanged. The other data collection forms would have to be modified to address the specific roadside feature/object with more specific and greater details. 5.6.3 Organization The sponsorship and organization of a special study data col- lection effort would be similar to those of the continuous sam- pling subsystem. The program is best sponsored by AASHTO and administered through NCHRP. The conduct of the study would be handled by an outside contractor and coordinated with NASS while a project panel or a technical advisory com- mittee would provide guidance and direction to the contractor and review the study progress and results.

64 If both the continuous sampling subsystem and the special study subsystem are implemented, then the most logical arrangement is to hire a new investigator for each participat- ing PSU since the special study cases are mostly sampled out- side of CDS cases. Similarly, new personnel would have to be hired at the two Zone Centers to handle the quality control of the collected data and coding of additional information for the special study. The additional staff at the PSUs and Zone Centers would ensure that the regular CDS operation will not be adversely affected. The outside contractor would continue to handle the coding of additional information, reconstruc- tion of the cases, and the performance assessment. In addition to the training required for the regular CDS data collection and the continuous sampling subsystem, both PSU investigators and Zone Center personnel assigned to the spe- cial study data collection effort would require special training in order to collect and quality control the specific and detailed data for the special study. The training would be conducted by the outside contractor on data elements, coding instructions, and field procedures specific to the special study data collection effort. The training should include both classroom lectures and field training as well as on-the-job training. 5.7 Summary A long-term data collection plan on single-vehicle, ran-off- road crashes is proposed. The proposed plan is built around the NASS CDS data collection system, including both within- sample supplemental data collection and outside-sample spe- cial studies. The efforts would be prospective in nature, i.e., the cases would be sampled from new crashes and consist of two major subsystems or components: 1. A continuous sampling subsystem intended for a general database to address items of interest pertaining to single- vehicle, ran-off-road crashes. The cases would be selected from within the CDS sample and supplement the basic CDS data with additional data on roadway, roadside, and struck-object characteristics. In addition, the cases would be reconstructed to estimate impact conditions and vehicle trajectories. 2. An ad hoc special study subsystem intended to address specific questions or roadside safety features. The cases would be selected from both within and outside the CDS sample to assure sufficient sample size within a reasonable period of time. In addition to the basic CDS data and the supplemental field data on roadway and roadside charac- teristics, detailed information would be collected on the safety device of interest. Again, the cases would be recon- structed to the extent possible to estimate impact condi- tions and vehicle trajectories. The data collection effort is best sponsored by AASHTO and administered through NCHRP. An outside contractor would be hired to conduct the study and to coordinate the data col- lection effort with NASS. A project panel, or a technical advi- sory committee composed of management-level personnel from the sponsoring agency and NASS, would oversee the overall conduct of the study, provide guidance and direction to the contractor, and review the study progress and results. If only the continuous sampling subsystem is to be imple- mented, then the most logical arrangement is for existing NASS investigators to collect the data since the additional time for the supplemental data would not be sufficient to require new staff. Quality control would be conducted by Zone Center personnel. It may be necessary to hire new Zone Center staff to handle the additional work. Coding of addi- tional information, reconstruction of the cases, and assessment of the impact performance would be handled by the outside contractor. It is important to make sure that the additional work would not adversely affect the regular CDS operation. If both the continuous sampling subsystem and the special study subsystem are to be implemented, then the most logical arrangement is to hire a new investigator for each participating PSU. This new investigator would be trained not only in the collection of CDS data, but also supplemental data pertaining to the continuous sampling subsystem and the special study subsystem. Similarly, new personnel would be hired at the two Zone Centers to handle the quality control of the collected data and coding of additional information. The completed cases would then be forwarded to the outside contractor for addi- tional quality control and reconstruction.

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Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 665: Identification of Vehicular Impact Conditions Associated with Serious Ran-off-Road Crashes quantifies the characteristics of ran-off-road crashes and identifies appropriate impact conditions for use in full-scale crash testing.

Appendices A through F of NCHRP Report 665, which are as follows, are available online:

Appendix A: Annotated Bibliography

Appendix B: 1997–2001 NASS CDS Cases

Appendix C: Supplemental Data Collection Protocol

Appendix D: Database Content

Appendix E: Additional Tables, Plots, and Analysis Results

Appendix F: Proposed Data Collection Forms Continuous Sampling Subsystem

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