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On the other hand, if the special study subsystem is imple- to handle this task. First, the task requires considerable expert-
mented with the continuous sampling subsystem, then one ise and experience, which may be beyond the capability of the
new investigator per participating PSU would make immi- PSU investigators, particularly the new hires with little or no
nent sense. This additional investigator would be responsible experience. Second, the work would likely be more accurate
for collecting both the supplemental data on the continuous and consistent if handled by Zone Center personnel. Third,
sampling cases as well as the special study cases, although the one or more new persons can be hired at each of the two Zone
majority of the investigator's time would be devoted to special Centers specifically for this task of quality control and coding
study cases. of the additional information. This would minimize the con-
cern of adversely impacting the CDS operation.
5.3.2 Special Study Subsystem
5.3.4 Project Management
The general database developed under the continuous sam-
pling subsystem will be invaluable to addressing general trends It is envisioned that an outside contractor would be hired
and questions on single-vehicle, ran-off-road crashes. How- by the sponsoring agency to coordinate with NASS on the
ever, it lacks the detail and sample size to address specific ques- data collection effort. The key responsibilities for this con-
tions, such as the impact performance of guardrail terminals. tractor would include, but not be limited to:
As discussed previously, the level of detail on struck-object
characteristics will be limited for the supplemental data col- · Design of the data collection protocol for both the contin-
lected under the continuous sampling subsystem. Also, the uous sampling subsystem and the special study subsystem
number of cases involving a specific roadside feature will be · Reconstruction of the cases to estimate the impact speeds
relatively small since the cases are sampled within the CDS and conditions
sample and it will likely take a very long time before a suffi- · A second level of quality control of the supplemental data
cient sample size becomes available. collected
The special study subsystem is designed to handle these ad · Maintenance of the general database and special study
hoc studies. In contrast to the continuous sampling subsys- database
tem, a special study is tailored to a specific roadside feature. · Analysis of the data to address specific questions
Thus, the data elements, particularly those pertaining to the
roadside feature, can be designed to the desired level of detail. A project panel or a technical advisory committee, com-
Also, the sampling of the cases would be outside of the CDS posed of management-level personnel from the sponsoring
sample, thus assuring a sufficient sample size within a reason- agency and NASS, would oversee the overall conduct of the
able period of time. study. The panel would provide guidance and direction to the
As mentioned previously, a new investigator would be contractor and review the study progress and results.
hired specifically for the data collection effort at each partic-
ipating PSU. The investigator would first receive training
5.4 Pilot Study
similar to that of a NASS investigator so that the investigator
can collect the basic data elements for a CDS case. In addi- A pilot study was conducted to demonstrate the feasibility
tion, the investigator would receive special training to collect of such a long-term data collection effort to both the poten-
and code the new data elements for the continuous sampling tial sponsor and to NHTSA. Specifically, the objectives of this
subsystem and the special study being conducted. pilot study were to:
· Demonstrate the feasibility of integrating this long-term
5.3.3 Quality Control
data collection effort on ran-off-road crashes into the reg-
Two Zone Centers currently provide the quality control ular NASS CDS program.
and oversight of the PSUs in the CDS data collection effort. It · Identify and resolve any potential problems associated
is envisioned that the Zone Centers would serve the same role with this long-term data collection effort.
in the continuous sampling subsystem and the special study · Estimate time and manpower requirements associated
subsystem. with this long-term data collection effort.
One question is whether the additional coding on informa-
tion pertaining to impact conditions and vehicle trajectories
5.4.1 Scope
should be handled at the PSU level by the designated investiga-
tors or by Zone Center personnel. Either approach is workable, The pilot study covered only the continuous sampling sub-
but it may be more appropriate for the Zone Center personnel system within the CDS sample. The feasibility and costs of the
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special study subsystem outside of the CDS sample would · Supplemental Data Collection Form
vary greatly depending upon the specific nature of the study · Object Struck Data Collection Form
to be undertaken. Therefore, evaluation of the special study · Reconstruction Coding Form
subsystem is beyond the scope of the current study. The scope · Scene photographs
of the pilot study involved the conduct of a supplemental data
collection effort at a small number of PSUs for a limited A log form was developed to identify each case and its status
period of time. The same data collection protocol used for the (i.e., active or not active); track the additional time spent on the
current retrospective study was employed for this pilot study supplemental field data collection at the PSU level and on qual-
for the sake of simplicity. This eliminated the need to develop a ity control and reconstruction at the ZC level; and document
new data collection protocol and to retrain the PSU researchers any problems and provide comments. No training for the PSU
and Zone Center (ZC) personnel. researchers or ZC personnel was deemed necessary since they
It should be pointed out that the integrated supplemental were already familiar with the data collection protocol.
field data collection and reconstruction effort are actually eas- The supplemental data collection forms and reconstruction
ier and more efficient than the current retrospective study: coding forms were completed and submitted in hard copies.
The CDS data elements of the selected cases were obtained
· No wasted effort to re-familiarize the researchers and ZC from preliminary approved cases posted on the NHTSA web-
personnel with details of the old cases. site with a time lag of approximately six to eight weeks.
· No additional time to travel and locate the crash site.
· Scene evidence (e.g., damage to roadside hardware) avail-
5.4.3 Pilot Study Results
able for documentation.
· ZC staff can perform the reconstruction in conjunction As shown in Table 90, there were a total of 22 eligible cases
with their regular quality control effort in less time and during the nine-week study period, 16 cases for PSU 48 and
with greater accuracy. 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
More detailed descriptions of the pilot study are presented (83.3%) for PSU 78.
in the next section, followed by results of the study and con- For each sampled case, the PSU and Zone Center personnel
clusions and recommendations. 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,
5.4.2 Data Collection Protocol
including:
As mentioned previously, the same data collection proto-
col used for the current retrospective study was employed for · PSU
the pilot study with minor modifications. Highlights of the Field time to collect the additional data
data collection protocol are summarized as follows. Office time to process the additional data
Based on the frequency of single-vehicle, ran-off-road · Zone Center
crashes and availability of trained researchers, two PSUs were Time to quality control the additional data
selected for participation in the pilot study: PSU 48 and PSU Time to reconstruct the impact conditions other than
78. The time period for the pilot study was the nine weeks impact speed
from October 4, 2004, to December 4, 2004.
The cases were selected from within the CDS sample, i.e., Note that these times pertain to only the additional data
from cases that were already included in the CDS sample. The elements and not the time required for the NASS CDS data
sampling criteria were the same as the current supplemental collection effort. In addition, the researchers were asked to
data collection effort except for the completion requirement, note any problems or unusual events encountered in the field
i.e., single-vehicle, ran-off-road crashes on roadways with or office on the log form.
speed limit greater than or equal to 45 mph. In order to avoid Table 91 summarizes the additional time required for each
disruptions to the regular CDS data collection effort, each of these 16 sampled cases and their averages. As may be
researcher was limited to no more than one case per week. expected, the additional time varies greatly on a case-by-case
However, all eligible cases were documented for the report. basis, depending on the complexity of the crash and, to some
Thus, the maximum expected number of eligible cases was extent, the efficacy and expertise of the individual investiga-
limited to four per week, two cases per week from each PSU. tors. Overall, the time required for the additional work on the
The same data collection forms and procedures as the cur- supplemental data collection ranges from 60 to 255 minutes
rent effort were used for the pilot study, including: per case with an average of 135.3 minutes per case.
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Table 90. Number of eligible and sampled cases.
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 91. Additional time required.
Additional Time Required (Minutes)
Case Number PSU Zone Center
Quality Recon- Total
Field Office
Control struction
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
52.8 41.9 8.1 32.5 135.3
Average
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At the PSU level, the additional field time for collection of supplemental data collection effort for this pilot study. To
the supplemental data ranges from 20 to 120 minutes with an ensure completeness, the researchers were asked to enter
average of 52.8 minutes. The processing time in the office "None" if there are no problems or comments. The comments
ranges from 0 to 120 minutes with an average of 41.9 minutes. are tabulated in Table 92. Overall, there are no major com-
The combined field and office time at the PSU level ranges ments of concern. Some of the comments pertain to common
from 30 to 180 minutes with an average of 94.7 minutes. operational issues, such as scene evidence, photography, and
At the Zone Center level, the additional time for quality interference from traffic and Visio printer setup, which are not
control of the supplemental data ranges from 5 to 10 minutes specifically related to the supplemental data collection. Other
with an average of 8.1 minutes. The time needed to reconstruct comments pertained to definitions and procedural issues that
the impact conditions (except for impact speeds) ranges from can be easily remedied with some training, including:
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- · Multiple impacts
utes with an average of 40.6 minutes. · Impacts with more than one object in close proximity
The researchers were asked to report any problems or · Reference framework for lateral distance measurements of
unusual events encountered during different phases of this trajectory
Table 92. Summary of comments.
Case No. PSU Comments Zone Center Comments
I had to go back to the scene and redo my Visio printer setup. Had to "grab" missing
lateral measurements because I forgot to images from case.
04-48-235J
separate the rollover initiation, but that was the
researcher's fault. Other than that, no problems.
04-48-238K None. Visio printer setup.
None. Had to create an object form for 2nd object
04-48-246D
struck. Visio printer setup.
Two utility poles situated close beside each Visio printer setup. 2 extra object forms
04-48-253H
other were struck and coded as one event. added for Events 2 and 3.
Another crash occurred in same area / In-house Visio issue.
04-48-254B
deciphering evidence.
04-48-259K None. In-house Visio issue.
Difficult to place ID card in images on scene Reconstruction changed angle of departure
04-48-262C due to Interstate traffic. off barrier, so re-calculated FRP. (No scene
evidence at FRP.)
Vehicle departed right road edge and returned None.
04-48-265K to road to rollover. Slope measurements taken
at road departure.
None. Visio did not migrate properly. Had to create
04-48-267J
from printout copy.
04-48-274J None. Visio printer software issues.
Multiple events and scene evidence being Same Visio printer setup problem. Listed 3
contaminated made it difficult to determine events (that affected CG) only (not 6).
04-48-280K
impacts and locations. Laterals on a curve were changed to be
perpendicular to the curved road edge.
None. Had to annotate POD, etc. on Visio. Advised
04-78-134D
researcher how to do that "next time".
Had a hard time placing the cones in a straight 12 laterals taken from POD to FRP, not POD
04-78-140K
line from road edge to final rest. to POI. Had to re-calculate these from Visio.
Heavy rain and it caused delays in getting out to None.
04-78-143K
take images.
None. Researcher took 12 laterals from POD to
04-78-144J FRP. Re-computed 6 laterals from POD to
POI.
Researcher unsure how to fill in the Filled in subsequent reconstruction form for
04-78-148K
reconstruction form for events 2 and 3. researcher.
