Injuries resulting from motor vehicle crashes remain a major public health problem. These injuries cause unnecessary burden of increased taxes and insurance premiums. They can be prevented, or reduced, but only if we understand what the severity of these crashes is, and their associated health care costs. Crash data alone do not indicate the injury problem in terms of the medical and financial consequences. By linking crash, vehicle, and behavior characteristics to their specific medical and financial outcomes, we can identify prevention factors.

CODES evolved from a congressional mandate to report on the benefits of safety belts and motorcycle helmets. NHTSA has funded Alaska, Arizona, Connecticut, Delaware, Georgia, Hawaii, Iowa, Kentucky, Main, Maryland, Massachusetts, Minnesota, Missouri, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Dakota, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah and Wisconsin to link statewide crash and injury data. Probabilistic linkage techniques make it possible for the states to link large state data files in a phenomenally short amount of time at relatively low cost.

Here's how CODES works:

1. Crash and medical data are collected at the crash scene, en route to the emergency department, at the hospital or trauma center, and after discharge.
2. The type of injuries, their severity, and the costs incurred by persons injured in motor vehicle crashes are described and computerized.
3. These statewide data are linked and evaluated.

What do linked data tell us?

1. Linked data identify the types of injuries and the costs which result from specific driver, vehicle, and crash characteristics.

What do states need to implement CODES?

1. Computerized crash injury data (preferably edited statewide)
2. Descriptive information to identify persons involved in specific motor vehicle crashes
3. Sufficient microcomputer (or workstation) capability to process large state data files
4. Staff members who are experienced in working with the crash and injury state data
5. The equivalent of two full-time personnel for one month to link the state data.

What resources are available to assist states?

1. Technical assistance for states is available from NHTSA and provides CODES experts to advise how to obtain state data, resolve barriers related to confidentiality and privacy, and prepare the files for linkage. These CODES experts also provide assistance to establish an advisory committee to institutionalize data linkage, implement the probabilistic linkage software, perform the linkage, validate the linkage results, and assist in the developing of analytical uses for linked state data.

The CODES Model

1. Statewide, population-based, computerized data related to motor vehicle crashes for two calendar years:
2. Crash - Collected by police at the scene
3. EMS - Collected by EMTs who provide treatment at the scene and en route
4. Emergency Department/Hospital - Collected by physicians, nurses and others who provide treatment at the emergency department, in the hospital or outpatient setting.

Linked Data

1. Probabilistic linkage of the crash, hospital and either EMS or emergency department data so that persons involved and injured in a motor vehicle crash can be tracked from the scene through the health care system. Linkage also makes it possible to evaluate the medical and financial outcome for specific event, vehicle and person characteristics.
2. Additional state data such as driver licensing, vehicle registration, citation/conviction records, insurance claims, HMO/managed care data are also useful for linkage. Data elements chosen for linkage must include sufficient identifiers to discriminate among the events and the persons involved.

CODES is directed by:

1. CODES Board of Directors, the owners of the state data and responsible for all decisions related to confidentiality, management and release of the linked data.
2. CODES Advisory Board includes the data owners and major users of the linked data who review and advise on applications of the linked data.

Staff experienced in working with the crash and injury state data.

1. CODES provides extensive on-site training in probabilistic linkage.

Dedicated computer resources for linkage.

1. Funded by CODES.

Institutionalization of CODES within existing state agencies.

1. State support of routine linkage of state data.
2. Use of linked data for traffic safety decision making.

CODES Links on the Internet

Hawaii Missouri Oklahoma Pennsylvania South Carolina South Dakota Utah Wisconsin

CODES Document Links

Standardized Reporting Using CODES (PDF/1MB)

Problems, Solutions and Recommendations for Implementing CODES. (Adobe PDF/377K).

Compiled contributions from CODES states regarding problems, solutions and recommendations for implementing CODES.

Geographic Information Systems Using CODES Linked Data. (Adobe PDF/356K).

Represents information about Geographic Information Systems (GIS) and CODES linked data. The purpose of this information is to encourage other CODES states to expand CODES to include GIS.

Revised Catalog of Types of CODES Applications Implemented Using Linked State Data. (06/2000)

The latest updated compendium of analyses and reports by CODES states and NCSA, using the linked data. It is arranged by type of analysis, and provides contacts for obtaining the reports.

Report to Congress on Benefits of Safety Belts and Motorcycle Helmets, Based on Data from the Crash Outcome Data Evaluation System (CODES). (02/1996).

Provides person-specific, population-based outcome information used to evaluate the effectiveness of safety belts and motorcycle helmets in terms of mortality, morbidity, severity, and cost.

Why Data Linkage? (10/1996)

"Why Data Linkage" provides a complete but brief summary of what data linkage is, the various types of applications for linked data that have been identified and successfully implemented by the CODES states, and how interested states can obtain information about implementing CODES.

NHTSA Technical Report: The Crash Outcome Evaluation System (CODES). (01/1996)

Includes technical information about the probabilistic linkage and state specific results to serve as a background reference for the Report to Congress on Benefits of Safety Belts and Motorcycle Helmets.

Research Note: Crash Outcome Data Evaluation System (CODES) Project Safety Belts and Helmet Analysis. (02/1996)

Summarizes technical information about the data collection methodology, outcome measures, contributing factors considered, and how the state specific results were combined statistically to determine the benefits of safety belts and motorcycle helmets for the Report to Congress.

Methodology Application Document: Logistic Regression Using the CODES Data. (09/1996)

Provides background in Chi-Square Analysis and simple linear regression, introduces odds, odds ratios, logits, probabilities, relative risk, and effectiveness and gives examples of logistic regression. CODES data are used for the examples. Also available in WordPerfect 6.1 format, with hyperlinks (1.1 MB) .

Documents Available by Mail from NHTSA

Moore, M. Comparison of Young and Adult Driver Crashes in Alaska Using Linked Traffic Crash and Hospital Data. DOT HS 808. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, January 20, 1998.

Karlson, T., Bigelow, W. Beutel, P. Serious Lower Extremity Injuries from Motor Vehicle Crashes, Wisconsin 1991-1994. DOT HS 808 791. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, September 1998.

Castle, S., Woods, B. Using Linked Data To Evaluate Traumatic Brain Injuries in New Mexico. DOT HS 808 798. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, October 1998.

Allen, M., Weiss, H. Using Linked Data To Evaluate Hospital charges for Motor Vehicle Crash Victims in Pennsylvania. DOT HS 808 799. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, October 1998.

Allen, M., Weiss, H. Using Linked Data To Evaluate Collisions with Fixed Objects in Pennsylvania. DOT HS 808 800. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, October 1998.

Finison, K., DuBrow, R. Analysis of 1996 Maine Crashes Involving Young Adults. DOT HS 808 887. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, April 1999.

Finison, K., DuBrow, R. Analysis of Seat Belt Use and Outcomes in 1996 Maine Crashes. DOT HS 808 888. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, April 1999.

Finison, K., DuBrow, R. Analysis of 1996 Maine Crashes Involving Vehicles that Ran Off the Road. DOT HS 808 889. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, April 1999.

Zuckier, G., Jacobs, L., Thibeault, L. Using Linked Data To Evaluate Motor Vehicle Crashes Involving Elderly Drivers in Connecticut. DOT HS 808 971. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, September 1999.

Zuckier, G., Jacobs, L., Thibeault, L. Using Linked Data To Evaluate Medical and Financial Outcomes of Motor Vehicle Crashes in Connecticut. DOT HS 808 972. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, September 1999.

Zuckier, G., Jacobs, L., Thibeault, L. Using Linked Data To Evaluate Severity and Outcome of Injury by Type of Object Struck (First Object Struck Only) for Motor Vehicle Crashes in Connecticut. DOT HS 808 973. Washington, DC: Department of Transportation, National Highway Traffic Safety Administration, September 1999.

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