Case Study: North Dakota DOT Safety Belt Survey

Overview

Each state in the United States has inherent responsibilities handed down to them from the federal government. One annual requirement is to obtain an accurate and detailed count of safety belt usage of those traveling by motor vehicle within the state's borders.

The North Dakota Department of Transportation (ND-DOT) is a state government agency charged with the numerous roles involving intrastate travel. One significant role is that of traffic safety, and the Division of Drivers License and Traffic Safety (DL&TS) is the office responsible for making the state's roadways safer for travelers.

As a core requirement for receiving federal funding from the National Highway Traffic Safety Administration (NHTSA), the ND-DOT must provide the detailed annual report on safety belt use within the state. State Safety Belt Survey Report cover

Objectives

The purpose of North Dakota's studies of safety belt use is to provide statistically reliable data from which generalizations, comparative analyses, and recommendations can be drawn. Yet in the past, the ND-DOT had contracted with entities whose procedures for fulfilling the annual safety belt survey requirement lacked the level of detail desired. In addition, the methodology utilized was not considered accurate for cross-county comparison, as the observation period ran the duration of several months. Knowing that drivers' habits can certainly change over such a long period of time, change was necessary.

The ND-DOT approached DLN Consulting to invent a better mousetrap. The survey methodology was obsolete and desperately needed modernization, and the final report needed more accountability and details.

Activities

DLN went to work by heading straight "to the top" in contacting the National Center for Statistics and Analysis in Washington, D.C. DLN also worked closely with NHTSA to develop an entirely revised protocol, survey methodology, and observation guide used for training the individual observers.

Extensive steps were taken to ensure compliance with accepted standards of methodology for such projects, while customizing the techniques to best suit North Dakota's unique needs, and the ND-DOT's evaluation goals. A method was developed from which to base random sampling locations and Vehicle Miles Traveled in a weighted system that provided the most accurate assessment across the counties and regions of the state.

Just as importantly, the methodology DLN developed called for all observations to be done on the same days, in all sixteen counties surveyed, at virtually the same time of day. This change made the survey's results much more accurate and effective for comparisons between counties and regions.

DLN produced a complete report that documented the results of the survey of vehicle safety belt use in North Dakota. The report includes graphic and tabular formats, a detailed analytical narrative of the data and conclusions, and an analysis of the relative importance of the variables.

Analysis

With the revised annual Safety Belt Survey, the ND-DOT has an easy-to-digest report from which they can easily obtain not only overall safety belt usage rates, but also vehicle-, gender-, regional-, roadway-, and county-specific figures. This level of detail has allowed the ND-DOT to more accurately determine the best placement for its occupant protection funding, and to better identify the effectiveness of ongoing efforts.

Overall, the changes DLN Consulting recommended and implemented for the ND-DOT's annual safety belt survey brought true credibility and respect for North Dakota's final report. This has allowed the state to compete more effectively for federal funding, and has set a benchmark from which all future surveys would be measured.

DLN Consulting has been contracted to oversee and execute each annual safety belt survey for North Dakota since, and has advised other states in improving their respective methodology practices.

Summary of ND Safety Belt Survey

The results of the 2006 North Dakota statewide safety belt survey are summarized for selected variables in the following table and the discussion that follows. The table contains the raw frequencies and the weighted percent belted for the value of each variable. The weighted percents are adjusted to account for sampling probabilities and estimates of vehicle miles traveled for the counties and the sites that are included in this survey.

The 2006 safety belt utilization rate of 79.0% represents a moderate increase of 2.7 percentage points over the 2005 rate. This is part of the steady increase in safety belt use in North Dakota, with an average increase of 3 to 4 percentage points between 1999 and 2006. The overall rate is largely dependent on the behavior of drivers who outnumber passengers by more than six to one in the 2006 survey.
Safety belt use increased over the 2005 rates for all four of the regions of the state, with the highest increases in the northern quadrants of the state. However, the Southeast quadrant continued to have the highest rate of safety belt use, which is significant because the highest number of observations also come from the Southeast.
Safety belt use increased over the 2005 rates for both urban and rural sites. However, as is typical, the rate is higher in 2006 for rural sites than for urban sites.
Safety belt use on interstate roadways is considerably higher than the rates for federal roadways, with the lowest rates for state-maintained roadways.
Safety belt use rates are highest for occupants of vans and SUVs, with a slightly lower rate for occupants of automobiles. While the rate is much lower for occupants of pickup trucks, the use rate increased by more than five percent over the rate in 2005.
Female vehicle occupants are much more likely to be observed wearing safety belts in 2006. This result is typical of safety belt use surveys in North Dakota.

Contact DLN Consulting today for more information on how our Survey Methodology and Evaluation Analysis services can benefit your organization as it did for the North Dakota Department of Transportation.