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3.4.2.1 Geographic Location Identifiers

Identifiers such as state, county, city, and highway number, recorded by TIFA, HMIRS and MCMIS, provide links to actual crashes; however, this location information is not accurate enough to provide roadway information. By providing fields for crash location coordinates (latitude and longitude), additional information, such as number of lanes or divided highway, could be determined. Coordinate information should be readily available as most operators or police officers use devices that provide location information.

Additional fields that may be useful to include are the ones that indicate whether the crash occurred in a construction zone, on a bridge, or under an overpass.

3.4.2.2 Relational Location Descriptors

While the GES database does not provide location identifiers in the crash record, descriptions of the location of the accident in relation to the roadway and nearest junction are recorded. TIFA records contain a geographic code, type of route signing (e.g., interstate, U.S. highway, state highway, county road), traffic way identifiers, mile point to the nearest 0.1 mile, and latitude and longitude in decimal degree format. Additionally, the accident’s relation to a junction (e.g., at an intersection) and relation to roadway (e.g., on a shoulder) are recorded.

Similarly, the RSI-AAR TCAD records include the location of the nearest railroad station, the state or province, and the type of track. Information concerning the roadway design is also recorded.

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3.4.2.3 Time Descriptors

The date of the incident facilitates referencing a particular crash across multiple databases if report numbers are not provided. Recording the year of the crash is important for a variety of reasons including understanding what regulatory requirements might be in place, what technology is in use, and to monitor trends. Additionally, the amount of traffic on the road often depends on the month, day of week, and hour. Therefore, if the

denominator used is annual average daily traffic (AADT), adjustments can be made to account for peak or off-peak traffic. Furthermore, information concerning the date, hour, and minute of the crash enables light levels to be determined and recorded.

3.4.2.4 Roadway Descriptors

GES includes roadway variables such as access control, number of travel lanes, alignment, profile, traffic control device, and speed limit. TIFA records include type of land use, whether the crash occurred on the National Highway System or within a special

jurisdiction, roadway function class, whether the traffic way was divided, the number of travel lanes, roadway speed limit, roadway profile, alignment and surface type, traffic control device (if applicable), and whether the traffic controls were functioning. While not

appropriate for direct use, highway package performance may be influenced by variables such as highway class, level of service, type of pavement, type of median, and type of lane markers. On the other hand, the RSI-AAR TCAD only records the railroad responsible for track maintenance.

3.4.2.5 Population Density

GES includes variables describing the population density. This information provides an indication of both roadway design and the amount of traffic anticipated to be on the road.

3.4.2.6 Driving Conditions

Driving conditions influence highway risk because poor driving conditions can affect the performance of a driver or vehicle. For example, driving on dry roads as opposed to wet or icy roads is preferable, but not always possible. The type of crash resulting from wet or icy roads has different characteristics than the type of crash resulting from dry road driving conditions. The following roadway conditions are currently recorded:

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 Light Condition. The general light conditions at the time of the crash, including roadway illumination fixtures, is recorded in MCMIS and GES (both obtained from Police Accident Reports).

 Temperature. The RSI-AAR TCAD records the temperature at the time of the crash.

 Weather Condition. The GES, MCMIS, and HMIRS record weather (general atmospheric) conditions at the time of the crash.

 Road Surface Condition. The road surface condition, recorded in GES and MCMIS databases, records whether the road was dry or wet or covered in snow, slush, ice, sand, dirt or oil at the time of the crash. These conditions influence the amount of friction between tires and road surface.

 Work Zone. Driving in construction zones may affect the risk of transporting hazardous materials. Factors such as altered driving patterns, smaller lane sizes, uneven lanes, and loose stones/construction debris may be scattered along the roadway surface. GES includes a variable for work zone.

 School Bus. The presence of a school bus can change traffic patterns and cause vehicles to stop relatively unexpectedly. Therefore, hazmat risk may be affected. This variable is included in the GES database.

3.4.2.7 Number of Vehicles Involved

GES, TIFA, and MCMIS include a set of variables recording the number of vehicles involved in the accident. The number of vehicles includes all trucks, buses and other vehicles, such as cars and bicycles, involved in the crash. The RSI-AAR TCAD records the number of railcars in the consist, the number of cars derailed, the location (in the train) of the first car involved, and the number of tank cars derailed. Generally, the greater the number of rail cars involved, the more severe the accident.

3.4.2.8 Number of People Involved

GES, TIFA and MCMIS also include a set of variables recording the number of motorists as well as the number of non-motorists involved in the crash. If the number of injuries or fatalities is used as a measure of the severity of the accident, the total number of

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people involved in the accident could be used as the denominator to establish the rate of injury for a given accident.

3.4.2.9 Event Descriptions

The crash or collision of motor vehicles is typically described in police accident reports as one of the following accident types based on the pre-crash situation (NTSB 2009):

 Single driver.

 Right side or left side road departure includes driving off the road, loss of control, loss of traction, or attempting to avoid a collision with another vehicle/pedestrian/animal.

 Forward impact includes striking a parked vehicle, stationary object, pedestrian or animal, or driving off the road as the road ends.

 Multiple vehicles, same traffic-way/same direction.

 Rear-ending includes striking a stopped vehicle, a slower moving vehicle or a decelerating vehicle.

 Forward impact includes striking a vehicle due to loss of control/traction or due to an attempt to avoid a collision with another vehicle/object.

 Sideswipe angle includes striking a vehicle in a different lane or striking a vehicle that is attempting to enter the lane.

 Multiple vehicles, same traffic-way/opposite direction.  Head-on collision due to a lateral move.

 Forward impact includes striking a vehicle due to loss of control/traction or due to an attempt to avoid a collision with another vehicle/object.

 Sideswipe collision due to a lateral move.

 Multiple vehicles, changing traffic-way/vehicle turning.

 Turning across path when originating from opposite direction (i.e., left-hand turn into oncoming traffic) or when originating from same direction.

 Turning into path in the same direction or in the opposite direction.  Multiple vehicles, intersecting paths (T-bone collisions).

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Both GES and MCMIS record the above-mentioned descriptions. HMRIS also records a description of events as well as plans for further examination of the incident in a narrative format. TIFA records contain more refined data including the first event causing injury/property damage and the manner of collision. Similarly, the RSI-AAR TCAD includes fields for accident type.

3.4.2.10 Vehicle Role

GES examines each vehicle involved and identifies the following variables:  Travel speed of each vehicle involved.

 Travel path of the vehicle involved both before and after a driver made a corrective action to avoid an accident.

 The critical event leading to the vehicle's first impact in the crash.  Vehicle’s action prior to the critical event.

 Corrective action the driver attempted to avoid the crash.

 Whether the vehicle was in control during various phases of the crash sequence including:

 Prior to the corrective action.  Following the corrective action.  Prior to the critical event.

 The initial point of impact that produced property damage or personal injury.  The event resulting in the most severe property damage or injury.

Similarly, TIFA records the truck’s travel speed, the first event causing injury or property damage, vehicle maneuver prior to accident, crash avoidance maneuver, the most harmful event, the events related to the record’s motor vehicle, and whether the vehicle struck another vehicle or was struck by another vehicle (if applicable).