METRAS method:Measuring and Recording the Traffic

Accident Sequence.

Jaime Sanmartín y Mª Teresa Tormo

[2]

[ Recording information from accidents]::

The accident is one of the most unfortunate incidents that can happen in traffic.

Collecting the key information on the TA characteristics and consequences is important in order to monitor how it evolves and to evaluate the preventive measures.

The collection, the record and the management of such information is complex and requires appropriate instruments that make this task entrusted to the traffic police easier.

[3]

[ A practical example]::

0). Two vehicles are circulating in a motorway in different carriageways.

1). The A vehicle (yellow one) leaves the road from the left

2). The A vehicle hits the centre guardrail

3). The A vehicle makes a frontal collision with the B vehicle that is circulating in the opposite carriageway

[4]

1). The A vehicle (yellow one) leaves the road from the left

2). The A vehicle hits the centre guardrail

3). The A vehicle makes a frontal collision with the B vehicle that is circulating in the opposite carriageway

[ A practical example]Classic classification of the accident type::

[5]

ONE SINGLE CATEGORY TO DEFINE THE ACCIDENT TYPE

According to the classic classification of the accident type, the previous examplecould be classified in several ways:

- 5.3 Running off by the left hitting the ditch

- 5.4 Running off by the left with another type of impact

- 2.2 Collision against bumper fence

- 3.1 Frontal collision

SEVERAL CRITERIONS TO SELECT THE ACCIDENT TYPECriterion of the first event of the accidentCriterion of severity of the injuriesCombinatorial criterion of elementsInfrastructure criterionOther criterions

The accident type information is not associated with any of the involved unit (vehicle/pedestrian).

[ A practical Example]Limitations of the classic definition::

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[ Limitations of the classic classification of the accident type ]::

The classical accident typology only allows to identify one event in only one category.

The selection criterion of a category may change according to the moment, the location, the circumstance, the research interests and even the accident characteristics.

It may also change depending on the observer and is consequently subjective and not much defined.

Difficult identification given the dynamic nature of the accident. It does not allow a realistic knowledge of what happened during the course of the accident.

It does not differentiate the first event from the most serious one.

It does not allow to link the type of accident or severity of the injury with fields or characteristics of the involved units, the drivers or the pedestrians.

[7]

[The METRAS (Measuring and Recording

Traffic Accident Sequence) alternative] ::

It integrates a structured, detailed and standardized sequential description of the accident to avoid the limitation of the classic category of accident type in the statistical questionnaires.

It considers that an accident is a complex process having a dynamic nature and that one single category does not allow its description.

It implies a generic structured protocol in order to collect the information related to the sequence of the events that take place in the space and in the time during the course of an accident, from a statistical perspective.

Each event is considered to be an important and identifiable incident in a system of pre-established categories, that make an accident.

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Prior action

Straight

Trajectory

…

Offence

Excess

speed

Other

veh. / driver

/ pedestrian

factors

none

21. Running off

by the left

Veh. Data

passenger car

3 years old

…

Situational data

- 8 of September 2006

- 15:00

- Motorway AP-7 km 398

- Sunny, no wind

- Road surface: dry and clean

- Free-flow traffic

- …

A Accident sequencing

There are not any situational factors

that have influence on the accident

Accident

location

A

A

Involved

units

B

A B

EventsMost serious

event

X

24. Collision with

the centre guardrail

1. Frontal collision,

being in

the opposite carriageway

2 seriously

injured persons

PRIOR STAGE CONFLICT STAGE

Veh. Data

Minibus

8 years old

…

Prior action

Straight

Trajectory

…

Offence

None

Other

veh. / driver

/ pedestrian

factors

none

1 fatality

…

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Secuenciación del accidente

MÉTODO METRAS DE SECUENCIACIÓN DEL ACCIDENTE

UNIDADES IMPLICADAS

EVENTOS SUCESO

MÁS GRAVE

CHOQUE CONTRA ELEMENTOS FIJOS DE LA VÍA 29. Rotonda 30. Refugio, isleta

31. Bordillo, acera 32. Bolardos

33. Señal de tráfico 34. Setos, arbustos

35. Árbol 36. Farola

37. Contenedor 38. Fuente o estatua

39. Parada de bus 40. Otros elementos de urbanización

41. Barrera de seguridad 42. Barrera de paso a nivel

43. Otros elementos de la vía

CHOQUE CONTRA ELEMENTOS FUERA DE LA VÍA 44. Casa, muro o edificio 45. Vegetación fuera de la vía

46. Otros elementos situados fuera de la vía: papeleras jardineras, bancos, elementos parque infantil, publicidad…)

VUELCO, INCENDIO, REVENTÓN, OTRO TIPO 47. Giros sobre sí mismo

48. Vueltas de tonel o de campana 49. Despeñamiento o caída por desmonte

50. Vuelco del vehículo en calzada propia 51. Vuelco del vehículo en calzada contraria

52. Vuelco del vehículo fuera de la vía 53. Incendio del vehículo

54. Reventón 55. Otro tipo de suceso

COLISIÓN ENTRE VEHÍCULOS 1. Colisión frontal 2. Colisión frontolateral afectando el lado derecho

3. Colisión frontolateral afectando el lado izquierdo 4. Colisión lateral o refleja

5. Raspado positivo 6. Raspado negativo =

7. Colisión por detrás, alcance o en caravana 8. Alcance inverso

10. Colisión posterior-lateral

ATROPELLO 11. Atropello a peatón

12. Atropello a animal

CAÍDA 13. Caída en la vía

14. Caída de pasajero dentro de bus

CHOQUE CONTRA OBSTÁCULO EN LA CALZADA 15. Elementos de obras

16. Conos u otros elementos de baliza móviles 17. Valla de defensa

18. Desprendimientos de piedra o vegetación 19. Vehículo detenido a la derecha

20. Vehículo detenido a la izquierda 21. Carga o elementos de otros vehículos

22. Vehículos implicados en accidente previo

SALIDA DE LA CALZADA 23. Salida por la derecha sin invasión de otra vía o calzada

24. Salida por la derecha invadiendo otra calzada o vía 25. Salida por la izquierda sin invasión de otra vía o calzada

26. Salida por la izquierda invadiendo otra calzada o vía 27. Salida de la calzada en línea recta

28. Retorno a la vía

TIPOS DE EVENTOS:

Ejemplar 1:

Ejemplar 2:

Ejemplar 3:

Unidades implicadas

Los vehículos se identificarán como V1, V2, V3, V...

Los peatones se identificarán como P1, P2, P3, P...

[The questionnaire on one sheet of paper]

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[ The METRAS alternative try] ::

A better knowledge of the accident reality but it does not have the same costs as the in-depth studies.

To allow drawing a bridge between the statistical studies and the accident reconstruction studies, raising an intermediate level of analysis.

To consider the accident as a final result of a process in which several events are caused because of previous actions, offences or errors from the persons involved in the accident, environmental conditions, the road, or the interaction between several elements present just before the start of the accident.

To consider each event as relevant or identifiable incident or happening in a system of pre-established categories that form an accident. It covers running off the road, collisions, running over, rollovers and fire of the vehicle.

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[ Results of this codification]

What is the METRAS method allowing ::

The information about the first event allows to identify whatfirst happened and then study the influence of the infrastructureconditions, the situational factors, the factors of the driver /pedestrian and of the vehicle to prevent the accidents. It could bea key element for the study of the active safety.

The information about the most serious event allows toknow the event that has caused the most serious consequencesfor the involved persons. This could be a key element for thestudy of the elements of passive safety.

Accident sequencing may allow to draw patterns of accidentrate for particular roads, vehicles and even drivers or pedestrians.

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[ The experience with the METRAS method]In Catalonia:: The SIDAT Project

PROCEDURE Each report is filled in by up to four different police agents. Each participating agent fills in accident sequences from different

level of complexity (number of events / units involved). A sample of 73 traffic accident reports, 55 agents that filled in the

data and a total number of 305 accident sequences is achieved.

RESULTS OF THE PILOT TEST UNDERSTANDING: Practically whole the agents do understand

the procedure. Around 80% correctly answer to the first event and the most

serious one. The reports sometimes do not have enough information, and may

be interpreted differently.

This pilot test showed very positive results as for theunderstanding of the method, easiness of completion, objectivity,both for motorway and urban area accidents.

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[ The experience with the METRAS method]In Spain:: Pilot National Statistical Questionnaire of DGT

The first stage: the police agents fill in the serious or fatalquestionnaires to evaluate from the archived accident reports withspecific characteristics that take place in their municipality lately (sample:69 agents and 315 serious or fatal questionnaires).

The second stage: the completion of the statistical questionnaires forthe accidents that happen during the pilot test week together withdocuments of evaluation of the difficulties and contents (sample 141questionnaires)

Results obtained from the pilot test:

The accident sequencing is correctly filled in for the 80,3% of thequestionnaires.

In 52,4% of the cases only one event is collected. In the remaining47,6% more than one event is recorded.

In the 11,8% of the questionnaires, the entire sequence of events isnot collected but the first one and the most serious one are shown.

Only for the 7,9% of the cases the selection of the events is not themost appropriate one.

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[ Backgrounds] ::

National Centre for Statistics (NCSA) and Analysis National Highway Traffic Safety Administration U.S. Department of Transportation (NHTCA). Sistema Automotor Nacional de Muestreo (NASS) --- GES (in-depth studies, starting from a sample).

INRETS (Institut National de Recherche sur les transports et leursécurité) ------ Sequential model of the accident. (In-depth studies). Brenac and Fleury (1999) define the typical scenario.

Amans et al. (2003) carry out a detailed study on the accidents from a macro perspective and an in-depth study. The macro analysis produces the current classification (the same), the in-depth study is necessary.

CARE report on the accident typology.

Accident models from the labor perspective. MAIM. Davies y Manning. From interviews (It does not fit to the traffic model).

CADAS (The common accident data set), Project: SafetyNet (2009)

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Thank you !!!!!

NOTES:

The Metraseis Award for the most innovative contribution in the field of the survey methodology was given to the “METRAS method of event sequencing in the field of traffic accident statistical questionnaire.” in the “IV Conference of Survey Methodology”, organized by the Public University of Navarre in Pamplona on the 20-22 of September 2006.

The complete study of this method is currently being finished as the doctoral thesis of Mª Teresa Tormo and will be presented and defended soon.

More information…

www.uv.es/metras