Crash Data Definitions & Geography Methodology

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Data Note: The geography used in reporting is the location where the crash event took place.

Measures

Crash - An event that produces an injury and/or property damage greater than $500 which occurs on or after a motor vehicle has left a public roadway and involves at least one motor vehicle in transport. Vehicle crashes occurring on private property are not included.

Passenger Vehicles - A grouping that includes passenger car, van, pick-up truck and/or SUVs.

Motorcycle – Every motor vehicle having a seat or saddle for the use of the rider and designed to travel on not more than three wheels in contact with the ground, including motorcycles, scooters and mini-bikes, also mopeds. Excludes farm and construction equipment and go carts.

Motor Vehicle - A self-propelled vehicle designed or adapted to be used on highways and streets that can transport one or more people or any material. Excludes farm or construction vehicles, all terrain vehicles, go carts and bicycles.

Occupant in a Motor Vehicle – Any person who is in or upon a motor vehicle including the driver, passengers and all people riding on the exterior of the vehicle, includes motorcycles and mopeds, excludes ATV, go-carts, farm and construction vehicles and bicycles. (for example passengers inside the bed of a pick-up truck).

Unrestrained Driver – A lap, shoulder or combination lap/shoulder belt not being used as a safety restraint by the driver as noted by the law enforcement officer on the crash report. Persons on motorcycles, mopeds, bicycles, farm and construction equipment, or all terrain vehicles are excluded. NOTE: Until July 1, 2010 pickup truck occupants were excluded by Georgia law from wearing seatbelts, but are included in the analysis.

Crash Severity

NOTE: The sum of the selections made individually will exceed the sum of the selections grouped as a whole.[Example: A crash has 1 fatality and 3 serious injuries, if selected individually the output would show two tables, 1 fatal crash and 1 serious injury crash, however grouped as a fatal and/or serious injury crash the result is one table with the total as 1 Fatal, Serious Injury crash.]

Fatal - A death occurred as a direct result of a crash within the 30 days following a crash. Georgia crash data differs from national data by including the death of a fetus.

Serious Injury - Any person involved with the crash reported with a serious (incapacitating) injury.

Mild Injury Any person involved with the crash reported as visibly injured (not incapacitating) or has a complaint about an injury (possible, not visible).

Property Damage Only - A police-reported crash involving a motor vehicle in transport on a public roadway in which there is property damage of at least $500 with no reported injuries or deaths.

Road of Occurrence

The road on which the event occurred based upon the road type designation.

Interstates - The federal designated Interstate Highway System.

State Roads - All roads assigned a state route number, for which the state is responsible for maintenance, excluding Interstates.

Local Roads - County and City roads and streets where the local government is responsible for maintenance.

Initial Type of Collision

Non-collision - A group of crashes where the initial event involved a single vehicle that was not a collision. Examples are: fire, immersion, overturn, and falls from a vehicle.

Collision With Moving Object - Motor vehicles and objects that are moving or capable of moving. Includes stalled, parked, disabled and abandoned vehicles, bicycles, pedestrians, animals and trains.

Moving Object - Motor vehicles and objects that are moving or capable of moving. Includes stalled, parked, disabled and abandoned vehicles, bicycles, pedestrians, animals and trains.

Motor Vehicle - A self-propelled vehicle designed or adapted to be used on highways and streets that can transport one or more people or any material. Excludes farm or construction vehicles, all terrain vehicles, go carts and bicycles.

Collision With Fixed Object - Stationary structures or substantial vegetation attached to the terrain. Mailboxes, telephone poles and trees would be considered fixed objects.

Geography

GA Senate Districts – Electoral districts from which State Senators are elected. The Georgia Constitution limits the number to not more than 56 single member districts. Senate districts are apportioned based on population. Source: Georgia Legislative and Congressional Reapportionment Office, 2012.

GA House Districts-- Electoral districts from which State Representatives are elected. The Georgia Constitution requires not less than 180 Representatives apportioned by population from representative districts. Source: Georgia Legislative and Congressional Reapportionment Office, 2012.

Georgia Department of Transportation Districts (GDOT Districts) - GDOT has broken up the state of Georgia into districts for the planning, design, construction and maintenance of the state and federal highways in their region. Source: Georgia Department of Transportation, 2006

Metropolitan Planning Organization (MPO) - MPOs, which have responsibility for planning, programming and coordination of federal highway and transit investments in urbanized areas of over 50,000 population. Source: Atlanta Regional Planning Commission, 2000

School Districts - School districts are a form of special-purpose district which serve to operate local public primary and secondary schools within a designated area approved by the Georgia General Assembly. Source: Georgia Department of Education, 2008

Contributing Factors (Factors Contributing to the Crash)

Any circumstance or driver behavior that appears to the law enforcement officer at the crash scene to have contributed to the crash of the vehicle. There may be multiple contributing factors for each crash; therefore there can be more contributing circumstances than crashes occurring in any given year. Selecting a contributing factor and a vehicle type limits results to just crashes where the contributing factor is matched to the vehicle type.

DATA NOTE: Only the top 5 factors, excluding “No Contributing Factors”, “DUI”, Driver Condition” and “Other”, related to fatal or injury crashes are available as subcategory selections. Only the first factor reported for a vehicle is included for data analysis. “No Contributing Factors” indicates that nothing happened beyond the normal travel behavior and therefore is not available as a subcategory selection.  The factors of “DUI” and “Driver Condition” are not available due to underreporting. The factor “Other” is not available due to vagueness. Currently Georgia records 27 factors that could contribute to a crash. Currently cell phones, as a contributing factor, appear less than 0.1 percent of the time.

Table Of Selected Contributing Factors (Factors Contributing to the Crash)
All Factors	Includes all factors, including “No Contributing Factors”, “DUI” and “Other”.
Changed Lanes Improperly	Driver did not follow procedures set forth involving the use of signals or safe clearances required when changing lanes.
Disregard Stop Sign/Signal	Driver did not bring the vehicle to a motionless state prior to moving forward at a stop sign, traffic light or other device signaling a complete stop.
Driver Lost Control	Driver was unable to control at least the direction or speed of the vehicle
Exceeding Speed Limit	Vehicle was traveling faster than the posted speed limit for the section of road where the crash occurred.
Failed to Yield	Driver failed to properly yield to another vehicle as required.
Following too Close	Driver was positioned at a distance behind another motor vehicle or non-occupant (such as a pedestrian or bicyclist) that was too close to permit safe response to any change.
Object or Animal	An object, not a vehicle or pedestrian, or animal, deer appeared in the roadway impairing the use of the vehicle.
Too Fast for Conditions	Vehicle was traveling faster than was considered safe for the environmental conditions of the roadway.
Weather Conditions	Conditions due to different aspects of weather impaired the use of the vehicle.
Wrong Side of Road	Vehicle was traveling in traffic lanes designated for oncoming traffic.

Metrics

Data Classification:

The quantiles method of data classification is:

• Data values for each enumeration unit (e.g. county or census tract) are ranked from lowest to highest.
• The total number of values is divided by the number of classes specified by the user to determine how many values each class will contain. The object is to obtain a roughly equal number of data values within each class. For example, if you have 100 census tracts and the tract data values are to be classed into 5 classes, each class will have 20 values (100/5 = 20).
• In some cases, an equal number of values will not be placed into each class. For instance, if there are an odd number of enumeration units some classes will have a larger number of data values than others. If data values for the 159 counties of Georgia are divided into 4 classes, then some classes might have 39 data values while others have 40. In addition, identical data values are maintained within the same classes. Continuing the Georgia county example, if 45 of the lowest data values are 0, then the lowest class will have 45 data values all with a value of 0.

The quantiles method of classification is used because:

• Quantiles classification is one of the simplest methods of classification and is easy to understand and interpret.
• Classes are usually centered on the median, a measure of central tendency, and "they group enumeration units above and below the median into classes with equal frequencies regardless of their values." This makes maps easier to compare with one another.
• Many health-related measures are distributed normally (i.e. a large number of values falling near the middle of the data range with a smaller number of values on the low and high ends of the data range) making quantiles classification a logical classification method.

Source: Brewer and Pickle. Evaluation of Methods for Classifying Epidemiological Data on Choropleth Maps in a Series. Annals of the Association of American Geographers, 92(4), 2002, pp. 662-681.

V1.4 (03/15/2012)