Chapter 3 - Accident and Roadway Records
Section 3-01 - General Information
Three elements are considered in accident analysis:
1. The driver;
2. The vehicle; and
3. The roadway and its related environment.
Accident records contain information relating to each of these three elements that may be studied by the engineer
Title 23 United States Code (USC) 402, enacted in 1966 and administered through Title 23 Code of Federal Regulations (CFR) 1204.4, and California Vehicle Code (CVC) Section 2900 et seq. requires the State of California to have a data collection system as part of the process to reduce the number and/or severity of accidents on roads in the State of California.
In response to Title 23, USC 402, the State of California developed the Traffic Collision Reports (TCR's) used by police agencies to collect and compile accident data. When the State developed the TCR's, they also developed the accident database (SWITRS) that resulted from the data collected and compiled from the traffic collisions reports. The State also developed the Traffic Accident Surveillance and Analysis System (TASAS) used by the California Department of Transportation (Caltrans) to analyze accident, traffic, and highway data collected and compiled by Caltrans.
Title 23 USC 152, enacted in 1973, administered through Title 23 CFR 924, requires the State of California to have a process whereby, through the use of a survey of all public roads, the responsible agencies of the State will identify and analyze locations, then prioritize, schedule, implement and evaluate safety improvements to roadways which are intended to reduce the number and/or severity of accidents on all public roads.
In response to Title 23 USC 152, the State of California has developed a process that utilizes the TASAS data base, including the accident information collected and compiled into it, to effectively reduce the number and severity of accidents on all highways under the jurisdiction of the State. To aid the further analysis of locations investigated, Caltrans maintains a copy of the TCR's.
Absolutely critical to the process developed by the State to meet the needs of the above Federal laws are the Traffic Collision Report utilized in the date bases maintained by Caltrans, the California Department of Highway Patrol (CHP) and numerous local agencies within the State of California. While the reader is referred to the TASAS data system for general information on trends and location to be studied, Traffic Collision Reports must be used for the detailed analysis necessary for the development of projects.
The California Vehicle Code (CVC) Section 20008, Duty to Report Accidents, requires a centralized collection of data for fatal and injury motor vehicle accidents. The driver of a vehicle involved in an injury or fatal accident is required to make (or cause to be made) a written report within 24 hours after the incident. Local police units are required to forward reports for the previous month to the California Department of Highway Patrol (CHP) in Sacramento by the fifth day of the month.
16000 (CVC), Report Required, requires the driver of every motor vehicle involved in an incident which resulted
in damage to the property of any one person in excess of $500 or in bodily injury or in death of any person shall
within 10 days report the accident on an approved form to the California Department of Motor Vehicles (DMV).
3-01.3 Reporting Level
The reporting level in the State of California varies over a broad range. Factors having a significant influence on reporting level are as follows:
Section 3-02 - Accident Reports
Accident Report forms are designed by various jurisdictions to satisfy various objectives.
The Federal Highway Safety Program Standards require that accident records systems maintained on a local level must be compatible with the statewide system which in turn must interface with elements of a national system. This requirement plus the increased study and analysis on a county-wide, regional and statewide basis give weight to the desirability of a small number of acceptable “standard” forms.
The most widely used form in the State of California is the form CHP-555. This form, the CHP Collision Investigation
Manual (CIM), and training in usage of the forms and manual are provided by the CHP at no cost to the local police
agencies to encourage complete and uniform reporting.
3-02.3 Accident Reports Confidential
Section 20014 of the Vehicle Code requires reports made to the CHP shall be avilable for the confidential use of the Department of Motor Vehicles, Caltrans, and local authorities having jurisdiction over highways. Information from individual reports and/or data should be considered as confidential.
Summary data and copies of reports may be studied by agents of non-public agencies under controlled conditions for valid research purposes.
Section 3-03 - Accident Record Systems
Various cities within the State of California have had experience with several types of records systems. The
system that best fulfills the requirements of a particular jurisdiction can vary from a manual plotting and filing
system for a compact area with very low traffic volumes, to a very complex computerized system for a large urban
area or statewide agency.
3-03.2 Manual Accident Record System
The simplest manual system may consist of a pin map (accidents are plotted) and an accident file (reports are stored in date order or report number order, or a combination of both). A card or binder index is created for the reports. See Figure 3-1.
The pin map may use pins of different size and color to indicate months of the year and accident severity. Manual
systems are satisfactory where the volume of data is very modest and the cost of electronic data processing equipment
is not warranted.
3-03.3 Electronic Data Processing (EDP) Accident Record Systems
As the volume of data increases, manual systems become cumbersome and labor intensive and conversion to EDP becomes advantageous.
In conversion, a considerable effort must be expended to convert at least a portion of the manual system file into a historical EDP accident data base.
The same effort of conversion to create an historical accident data base is sometimes required when an elementary EDP system is modified or is replaced by a more sophisticated system.
An example of a very large basic EDP system is the “Statewide Integrated Traffic Records System” (SWITRS) administered
by the California Highway Patrol. The Caltrans “Traffic Accident Surveillance and Analysis System” (TASAS) is an
example of a large dual data base EDP system. California counties or cities with large EDP systems include Alameda
County and the cities of Los Angeles, San Diego and San Jose.
3-03.4 SWITRS General
The Statewide Integrated Traffic Records System (SWITRS) is a statewide records system. SWITRS is a centralized accumulation of data for fatal and injury motor vehicle traffic accidents. In addition, a large proportion of the reported property damage only accidents are also processed into SWITRS. The reports are generated by over 100 CHP areas and over 500 city police departments, sheriffs offices and other local jurisdictions.
The processed volume of reports is about 2,500 per working day. All reports are checked for completeness, coded,
key punched and processed into a computer data base. The computerized data is then available for quarterly and
special reports for participating cities and counties and other State agencies.
3-03.5 SWITRS Data to DMV
The California Department of Motor Vehicles (DMV) receives driver related data for its driver record files. All accidents processed through SWITRS have information transferred to drivers licenses and this becomes part of public record. This information can be made available to authorized agencies by contacting DMV.
3-03.6 SWITRS Data to Caltrans
State highway related collision reports receive additional coding as to objects struck and location details. Caltrans receives this State highway related data on a weekly basis for the Traffic Accident Surveillance and Analysis System (TASAS). The accident data transmitted to Caltrans does not contain names, drivers license numbers, addresses, vehicle license numbers, or data on age and sex of drivers and victims.
3-03.7 SWITRS Quarterly Output Reports
SWITRS produces eight quarterly reports several weeks after the end of the quarter as follows:
Report No. 1 - Type of involved party for accidents and victims.
Report No. 2 - Accidents by day and hour of day.
Report No. 3 - Primary collision factors for accidents and victims.
Report No. 4 - Motorcycle, bicycle, and pedestrian accidents and victims by time of day.
Report No. 5 - Alcohol involvement by age and sobriety of involved party and by accident type.
Report No. 6 - Pedestrian involved accidents, location details and victim data.
Report No. 7 - Bicyclist involved accidents, location details and victim data.
Report No. 8 - Accident location details and involved party data year to date.
Examples of each of the preceding reports and a discussion of the data items are contained in the SWITRS Users Guide available from the California Highway Patrol.
Reports 1 through 5 have parts A and B which are cumulative year to date, and latest quarter, respectively.
These reports (1 through 5) are statistical summaries only, whereas reports 6, 7 and 8 are individual listings.
The year end Report 8 could be used by local authorities for traffic engineering evaluations.
3-03.8 SWITRS Output Reports and Other Services
Detailed explanations of other SWITRS reports are contained in the SWITRS Users Guide, Chapters 4 and 5. One report that may be of use for traffic accident analysis is the General Retrieval Program (GRP). If specific data is required for traffic analysis or special research studies, the data may be obtained by use of GRP. Most of the collision report data can be obtained by GRP and can be formatted to an individual listing or a summary listing.
Section 3-04 - Caltrans Traffic Accident Surveillance and Analysis System (TASAS)
3-04.1 TASAS General
TASAS is a sophisticated version of an EDP traffic records system. It has an accident data base (AXDB), linked to a highway data base (HDB) which contains description elements of highway segments, intersections and ramps, access control, traffic volumes and other data. TASAS serves the needs of many offices within Caltrans and also provides roadway and/or accident information for other associated State and local agencies.
Detailed instructions as to coding, processing, and data retrieval are contained in the TASAS manuals, Section 100 and 200, TASAS Accident Data Base Support Processing Procedures, and other compilations.
3-04.2 TASAS Data Bases
All of the records in the TASAS data bases are stored in a manner that each record can be accessed directly. The two major data bases are as follows:
1. TASAS Accident Data Base (AXDB).
2. TASAS Highway Data Base (HDB).
Section 3-05 - TASAS Accident Data (AXDB)
3-05.1 AXDB General
This data base contains specific data for accidents that are State highway related. Each accident record contains a ramp, intersection or highway kilometer post marker address that is a key to tie to the Highway Data Base1 (HDB).
The master file contains records for 10 years plus the current year. The processing of collision reports is shown diagrammatically in Figure 3-2.
3-05.2 Content Accident Data Base
The individual records in the AXDB contain two basic types of information which are:
1. General accident information including:
b. Time and Date
d. Primary Collision Factor
e. Environmental Items
f. Roadway Conditions
g. Type of Collision
h. Number of Vehicles Involved
2. Information for each party including:
a. Party Type
b. Condition of Party
c. Actions of Party
d. Casualties Per Party
There are some AXDB records that do not contain any “party” information and only partial general accident information.
Each accident record may contain an entry for each party up to a maximum of nine.
3-05.3 Responsibility for Maintaining and Updating AXDB
The general responsibilities of Headquarters and District Traffic Branches for the Accident Data Base are as follows:
A. HEADQUARTERS RESPONSIBILITIES:
B. DISTRICT RESPONSIBILITIES:
3-05.4 TASAS Accident Output Reports
TASAS provides the following output reports:
1. TASAS Selective Accident Retrieval (TSAR) - Furnished on Request.
A detailed list of accidents and/or summary is available for any type or types of accidents on any section of highway, any ramp or any intersection in the State Highway System. Accidents may be selected by location, highway characteristics, accident data codes or any combination of these.
2. Cumulative Number of Accidents by Kilometer Post Marker1 (Table A) - Furnished Annually.
Table A reports include cumulative totals for two time periods, 12 months and 36 months.
3. Selective Accident Rate Calculation (Table B) - Furnished on Request.
Table B reports for accident data calculations are available for any highway or section of highway, any or all ramps, any or all intersections for any time period specified. The report shows both actual and average rates. The report also shows total accidents, fatalities, injuries, multi-vehicles, wet, dark, persons killed and injured and the significance.
4. High Accident Concentration Locations (Table C) - Furnished Quarterly.
Table C reports list high accident concentration locations. It counts the total number of accidents for 3, 6, 12, 24, and 36 month periods. It also calculates the actual rate and shows the average rate for the 12 month period. This report does have the option to consider highway segment lengths of up to 0.8 km.1 Locations with total accidents of 4 or more and significance in the 3, 6, or 12 month period are flagged as requiring investigation.
5. Wet High Accident Concentration Locations (Wet Table C) - Furnished Annually.
Wet Table C Reports list high wet accident concentration locations. It counts the total number of accidents for the 3, 6, 12, 24 and 36 month periods. It also shows the number of average wet accidents and calculates the actual rate for the 36 month period. Locations with 3, 6, 9 or more accidents and significance in the 12, 24 or 36 month periods respectively are flagged as requiring investigation.
Examples of the retrieval process, TSAR and Tables A, B, C, and Wet Table C are shown in Figures 3-4 through 3-12.
Section 3-06 - TASAS Highway Data Base
3-06.1 HDB General
The Highway Data Base (HDB) contains the current and historical descriptions of approximately 20,000 intersections, 13,000 ramps, and 24,400 km of highway segments in the State system.1
3-06.2 HDB Content
The Highway Data Base contains intersection, ramp, and highway segment records which contain the following information:
- The highway records provide the detail, design and geometric features relating to the main line, including access control, roadbed and median information.
- The intersection records describe and identify all intersections in the State Highway System including control, lighting, type, main line and cross street ADT information.
- The ramp records identify the specific location of all ramps connected to the highway, the type of ramp configuration, on or off, rural or urban and ADT with history.
3-06.3 Responsibility for Maintaining and Updating
HDB (See Figure 3-13)
The responsibilities for maintaining and updating the Highway Data Base are assigned to Headquarters and District Traffic Divisions as follows:
A. HEADQUARTERS RESPONSIBILITIES
The Roadway Records Unit in Headquarters has the overall responsibility to maintain a Statewide Highway Data Base. All additions, deletions and corrections must be processed through this unit.
Specific responsibilities are as follows:
B. DISTRICT RESPONSIBILITIES
3-06.4 TASAS Highway Data Base Output Reports
1. Multi-Retrieval Highway Data Base TSRR (AXR330) - Furnished on Headquarters Request.
This program provides for the highway data base to be accessed and detailed records printed out for ramps, intersections and highway segments without having to access the accident file. The summary contains segment totals by various types and vehicle kilometers traveled. Selection of highway data base records may be made based upon various highway, intersection or ramp characteristics.
2. Actual Highway Data (AXRO85) - Furnished on Headquarters Request
This report is a record of the actual contents stored in the highway data base. There arefour formats available: Current, Current with History, Previous and Previous with History. The contents are similar to AXR156, and include descriptions of major highway points (junction of State routes, bridges, structures, etc.). Segment lengths, Federal aid designations, left and right roadbed information, median information, traffic volume data, various effective dates, and other data are also included.
3. Actual Intersection Data (AXR085) - Furnished on Headquarters Request
This report prints the detail information for all intersections on the State highway system currently open to traffic.
The following information is provided in this report:
There are four formats available for this report: Current, Current with History, Previous, and Previous with
4. Actual Ramp Data (AXR085) - Furnished on Headquarters request.
This report prints the detail information for ramps on the State highway system currently open to traffic. A ramp is defined as a roadway connecting two State highways (one of which is a freeway), or connecting a freeway to a local street. A collector road in an interchange area is coded as a ramp.
The following information is provided in this report:
5. Highway Characteristics Reference Table (AXRO82) - Furnished on Headquarters Request.
This report lists highway segments, intersections and ramps. The report is available in current alignment only, prior alignment only, or combined current and prior alignment format.
The following information is provided in this report:
6. California State Highway Log (AXR156) - Furnished Annually.
The California State Highway Log contains a record for significant highway points in the State highway system which existed at the end of the calendar year.
The following data is provided by this log:
Examples of some of the various TASAS output reports from the Highway Data Base are shown on Figures 3-14 and 3-15.
The following information regarding Kilometer Post Markers are for future application. This information will apply after the field conversion of existing markers and conversion of the Highway Data Base.
The existing markers in the field are in English units (miles). The markers in the field are not to be mixed, metric and English, nor is a dual system contemplated. Installation of new markers, replacement of missing markers, and correction (relocation) of existing markers will be done in English units (miles). The previous policies of calculation, lateral placement, and spacing for two lane roads and divided roads and rural and urban will remain effictive until such time as a full field conversion program is applied.
Section 3-07 - Kilometer Post Markers
The kilometer post markers in the field are used by traffic officers, maintenance forces and others to locate specific incidents or features with reference to the kilometer post marker system. The kilometer post marker is integral to the kilometer post marker system and shall not be used for additional marker functions. Other types of markers shall not be used as kilometer post markers. The kilometer post marker shall indicate the route, county, and kilometer post marker of the installation; only kilometer post markers shall contain the route and county designation.
Reference is made to Section 3-06.3 and Figure 3-13 of
this manual as to the responsibility for kilometer post markers.
3-07.2 Kilometer Post Marker Calculations
For Headquarters advertised projects the Roadway Records Unit of Headquarters Traffic shall calculate preliminary kilometer post marker values. After review and agreement by the District Traffic Branch, these kilometer post marker values are used to prepare plans for placement of kilometer post markers.
For projects not advertised through Headquarters, the District Traffic Branch shall be responsible for liaison
with District Construction, and/or Maintenance Branches, other agencies, etc., for obtaining data to update the
HDB and calculate kilometer post markers. This material is to be transmitted to the Roadway Record Unit in Headquarters
and after review and agreement between Headquarters and district the calculated kilometer post markers are used
to prepare plans or lists for placement of kilometer post markers.
3-07.3 Placement of Markers
A. Rural Areas (See Figure 3-16).
1. Two-Lane Roads.
Markers are placed 1.6 km apart on both sides of the highway, staggered by 0.8.
2. Divided Roads
Markers are placed 1.6 km apart on both sides of the highway at the same kilometer post marker location.
B. Urban Areas (See Figure 3-16).
1. Two-lane roads.
Markers are placed 0.8 km apart on each side of the highway, staggered by 0.4 km.
2. Divided roads.
Markers are placed 0.8 km apart on each side of the highway at the same kilometer post marker location.
3. See ‘D’ see below.
C. Maximum Spacing.
When a regular marker falls within 0.4 km of a landmark (bridge, etc.), the 1.6 km or 0.8 km marker may be omitted. The intent is to have kilometer post markers spaced no farther apart than 1.6 km on rural highways, or 0.8 km on urban highways. This is a maximum spacing. Additional markers may be placed in areas where it is desired to have additional highway reference points.
D. Incorporated or Suburban Areas.
Kilometer post markers may be omitted in communities with city-street characteristics of curb, gutter, sidewalks and local development. In these areas, intersecting streets would be used as reference points in lieu of markers.
E. Kilometer Post Marker at County Lines.
At county lines, the county names and kilometer post marker information are delineated on separate markers and mounted side-by-side on separate posts, facing both directions of traffic.
F. Kilometer Post Marker Equation.
3-07.4 Kilometer Post Markers for Structures
1. Kilometer Post Markers
Kilometer post marker or G11 signs shall be mounted on, or placed at bridge abutments and at the beginning of bridge rails.
On skewed structures the kilometer post marker will not necessarily be identical on each side of the highway. The kilometer post marker on each side of the highway is the kilometer point of the centerline opposite the marker location. See Figures 3-18 and 3-19.
2. Highway Log Kilometer Post Marker Values.
a. Overcrossing and Underpass.
The Highway Log kilometer post marker for an overcrossing or underpass is measured from the centerline or layout line of the structure where it intersects the centerline of the highway. This rule applies to all structures crossing over the highway regardless of the skew. See Figure 3-18.
b. Undercrossings, Overheads and Bridges.
Single Structure: The Highway Log kilometer post marker is measured along the construction line as shown on the contract plans. The value is assigned to the paving notch at the end of the structure. See Figure 3-19.
Divided or Separated Structures on Divided Highways: The Highway Log kilometer post marker is measured along the construction centerline of each structure. The value is assigned to the paving notch at the end of the structures. Depending on the width of the median and the skew, two kilometer post marker values may be assigned to each end. See Figure 3-19.
3-07.5 Plans for Placement of Kilometer Post Markers
The preparation of plans for placement of kilometer post markers shall be the responsibility of the District Traffic Branch. These plans may be combined with other traffic plans for striping, signing, etc., where possible. In some instances, plans may not be required and a list of markers to be placed may be sufficient.
Orders for kilometer post markers should be combined with orders for other types of markers whenever possible.
The orders should be placed well enough in advance to ensure that the markers will be in place when the facility
is opened to traffic.
3-07.6 Kilometer Post Markers
Dimensions, lettering and positioning standards are included in the Standard Plans.
Kilometer post markers shall not be reflectorized. If a kilometer post marker should fall within a line of guide
markers, it shall be placed in a manner that will not interfere with the guide marker pattern. Kilometer post markers
are not to be used as guide markers, clearance markers, culvert markers, etc.
3-07.7 Kilometer Post Marker Installation and Verification
Kilometer post markers shall be placed a minimum of 0.6 m and not more than 3.6 m beyond the edge of shoulder on the right side of the highway facing traffic. Generally, they should be placed in such a position as to minimize interference with maintenance.
When installed behind guardrail, the marker shall be placed so that the entire legend is legible from the road.
Stenciling of the kilometer post marker on concrete median barriers is permissible in addition to, but not in place of the regular kilometer post markers. This is an additional aid for maintenance and accident investigation forces.
All markers shall be located to an accuracy of 15 m on the ground. The value shown on the marker shall be to the nearest 0.015 of a kilometer (15 m), and shall reflect the kilometer point of the centerline opposite the marker location.
The District Traffic Branch shall have the responsibility to verify the accuracy of the placement of kilometer
post markers. Periodic field review and inspection should be conducted to repair or replace damaged or illegible
markers. Any markers found to be more than 15 m from the intended location must be relocated.
3-07.8 Correction of Existing Markers
Reports of incorrect kilometer post markers may originate from various sources. The District Traffic Branch and the Roadway Records Unit of Headquarters Traffic must be in agreement as to which field markers will be corrected and which accident records will be relocated before any action is initiated.
List of Figures:
Figure 3-1 Typical Accident Record System
Figure 3-2 Collision Report Flow Chart
Figure 3-3 Data Retrieval Process
Figure 3-4 TSAR Detail
Figure 3-5 TSAR Summary
Figure 3-6 TSAR Summary - Continued
Figure 3-7 TSAR Summary - Continued
Figure 3-8 TSAR Summary - Continued
Figure 3-9 TASAS Table A
Figure 3-10 TASAS Table B
Figure 3-11 TASAS Table C
Figure 3-12 TASAS Wet Table C
Figure 3-13 Highway Data Base Flow Chart
Figure 3-14 Typical Highway Data Base Report
Figure 3-15 Typical Highway Data Base Report
Figure 3-16 Placement of Kilometer Post Markers
Figure 3-17 Kilometer Post Marker Equations
Figure 3-18 Skewed Overcrossing
Figure 3-19 Kilometer Post Markers for Structures
End of Chapter 3
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