1340.5—Documentation requirements.
All sample design, data collection, and estimation procedures used in State surveys conducted in accordance with this part must be well documented. At a minimum, the documentation must:
(1)
Define all sampling units, with their measures of size;
(2)
Define what stratification was used at each stage of sampling and what methods were used for allocation of the sample units to the strata;
(3)
Explain how the sample size at each stage was determined;
(4)
List all samples units and their probabilities of selection; and
(5)
Describe how observation sites were assigned to observation time periods.
(1)
Define an observation period;
(2)
Define an observation site and what procedures were implemented when the observation site was not accessible on the date assigned;
(3)
Describe what vehicles were observed and what procedures were implemented when traffic was too heavy to observe all vehicles; and
(4)
Describe the data recording procedures.
(1)
Display the raw data and the weighted estimates;
(2)
For each estimate, provide an estimate of one standard error and an approximate 95 percent confidence interval; and
(3)
Describe how estimates were calculated and how variances were calculated.
Code of Federal Regulations
Effective Date Note:
At 76 FR 18056, Apr. 1, 2011, part 1340 was revised, effective May 2, 2011. For the convenience of the user, the revised text is set forth as follows:
PART 1340—UNIFORM CRITERIA FOR STATE OBSERVATIONAL SURVEYS OF SEAT BELT USE
§ 1340.5
Selection of observation sites.
(a)
Sampling frame requirements—
(1)
County coverage.
The sampling frame from which observation sites are selected shall include counties or county-equivalents (including tribal territories), as defined by the U.S. Census Bureau, that account for at least 85 percent of the State's passenger vehicle occupant fatalities, provided that the average of the last three, four or five years, at the State's option, of available Fatality Analysis Reporting System (FARS) data or State fatality data approved by NHTSA shall be used to determine the State's passenger vehicle occupant fatalities.
(2)
Road coverage.
(i)
States shall select observation sites from a database of road inventories approved by NHTSA or provided by NHTSA.
(ii)
Except as provided in paragraph (a)(2)(iii) of this section, all roads in the State shall be eligible for sampling. The sampling frame may not be limited only to roads having a stop sign, stop light or State-maintained roads.
(iii)
The sampling frame need not include: rural local roads, as classified by the Federal Highway Administration's Functional Classification Guidelines, in counties that are not within a Metropolitan Statistical Area (MSA), as published by the Office of Management and Budget; non-public roads; unnamed roads; unpaved roads; vehicular trails; access ramps; cul-de-sacs; traffic circles; or service drives.
Code of Federal Regulations
576
(b)
Sampling selection requirements.
The set of road segments selected for observation sites shall be chosen based on probability sampling, except that—
(1)
The specific observation site locations on the sampled road segments may be deterministically selected;
(2)
An alternate observation site may be used to replace an observation site selected based on probability sampling if it is located in the same county or county-equivalent, and has the same roadway classification (e.g., local road segment, collector road segment) when using the protocol of substitution and rescheduling of observation sites pursuant to paragraph (c) of this section.
(c)
Requirements for substitution and rescheduling of observation sites.
The survey design shall include at a minimum the following protocols:
(1)
Protocol when observation site is temporarily unavailable for data collection.
(i)
Observers shall return to the observation site at another time provided that it is on the same day of the week and at same time of the day or select an alternate observation site, as described in paragraph (b)(2) of this section, provided the data are collected on the same day and at approximately the same time as the originally-scheduled observation site.
(ii)
The original observation site must be used for future data collections.
(2)
Protocol when observation site is permanently unavailable for data collection.
(i)
Except as provided in paragraph (c)(2)(ii), another observation site shall be selected in accordance with paragraph (b) of this section.
(ii)
If it is not feasible to select another observation site based on probability sampling for the current data collection, an alternate observation site, as described in paragraph (b)(2) of this section, may be selected, provided the data is collected on the same day and at approximately the same time as the originally-scheduled observation site.
(iii)
For future data collections, another observation site must be selected based on probability sampling in accordance with paragraph (b) of this section.
(d)
Precision requirement.
The estimated seat belt use rate must have a standard error of no more than 2.5 percentage points.