Territorial safety study

Dans le document Transportation safety in urban areas (Page 109-112)

The previous pages of the guide stressed how the general method is applied in running a safety study dealing with specific and linear cases. These targeted and linear safety studies are generally justified by the concern to improve transport safety, without neglecting other aspects (environment, local life, organisation of the network and public transport, etc.).

How a request arises

The request for a territorial safety study is mainly related to :

• the development of local road safety policies, given concrete expression today by the drawing-up of the general guidance document (DGO). The issue study, completed by a further, more in-depth stage, is at the heart of the DGO, a reference document, asserting state policy for combating road safety issues at département level. In theory, towns are requested to take part in drawing up this document, which is the basis of a public policy whose objective deals exclusively with safety ;

• regional development policies which are expressed in the form of development projects, more significant projects possibly including a mobility project (urban renewal, etc.) or planning documents : territorial coherence scheme (SCoT), urban mobility plan (PDU), local town-planning document (PLU), etc.

Phase 1 – The safety issue and diagnosis study : methodological specificities

In the area of drawing up planning documents, safety is never the primary concern. It is only one concern among others. Performing various diagnoses (traffic, parking, etc.) implies cross-referencing the diagnoses in order to define overall objectives. The other special methodological feature of the territorial study, given the great number of accidents to be studied, is the difficulty of managing :

• on the one hand, the complicated nature of the analysis because of the large number of cases to be processed. This difficulty can be overcome, either by carrying out an issue study to define representative sectors or topic-based targets on which to carry out the diagnosis, or by taking into account in the diagnosis only the previous year’s accidents. If the number of cases is still too great, it is possible to carry out random sampling of accidents on the area being studied ;

• and on the other hand, summarising all the information, which can nevertheless also be facilitated by resorting to the concept of a standard accident scenario described in the first part of the present guide. Mapping the standard scenarios is advisable to make spatial analysis easier.

To conclude, carrying out a safety study on a territory requires the use of the entire method presented in the first part of the guide, in particular the constitution and mapping of scenarios.

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Recourse to data external to the accident reports, in particular so as to study the relationships between accidents, territory and networks, should not be neglected at any cost. Respecting the recommended approach makes it possible to learn as much as possible from analysing the accident cases studied. This is because expertise alone can never replace a detailed study of accidents.

On-site observation

In certain cases that are too demanding (accidents widely dispersed throughout the territory, etc.), it is possible to do without on-site observation. This is in particular the case for drawing up the DGOs whose study area covers the whole département. INRETS also recommends this in a document entitled

“Outil et méthodes” (Tools and methods, INRETS, n°3, page 25 : “It is possible not to systematically return to the site of each accident studied, if this is likely to complicate matters avoid in certain general studies, such as a diagnosis prior to a local safety action, the objective of which, as far as the infrastructure is concerned, is to be able to define general principles for action”).

Formulating courses of action

The actions must be appropriate for the context and the problem set. It is important to carefully assess their foreseeable effects on safety and on other aspects. This presupposes a certain amount of experience and knowledge1.

One must also be aware that the measures implemented generally produce repercussions beyond the project area. These possible repercussions, related, for example, to traffic diverted to a wider area, must obviously be taken into account and give rise, if necessary, to accompanying actions.

1 These reference or specialised works contain useful information for the choice of possible courses of action :

“ Sécurité des routes et des rues”, Setra-Certu, 1992 ;

“Ville plus sûre, quartiers sans accidents, réalisations, évaluations”, Certu, 1994 ;

“ Réduire la vitesse en agglomération”, Certu, 1989 ;

“ Sécurité et urbanisme”, Presses de l'ENPC, 1998 ;

“ Scénarios-types d’accident de piétons et éléments pour leur prévention”, INRETS, 2003 ;

“Gestion urbaine, sécurité routière et environnement”, INRETS, 2002.

Preventing potential malfunctions

Often the developments programmed in projects related to territorial studies (building a tram line, creating a bus line with a high level of service within the framework of a town planning document, etc.) considerably modify public space to such an extent that it might be thought that future accidents will no longer have anything in common with accidents in the past and that expertise alone will be sufficient. As things stand, it can be said that “all symptoms are not equal.

Some rare pieces of research which have compared the effectiveness of measures based on past accidents and the effectiveness of the expertise of engineers or

“traffic psychologists” alone have shown that past accidents were better predictors of future accidents than expert knowledge applied to the characteristics of the roads studied. Although in certain cases one has to make do without past accidents (in new projects) or with only a few rare accidents, it is especially important to recognise that in this case the danger which we are highlighting is more uncertain than when we can make more use of past accidents. For this reason it might be preferable to contrast "uncertain"

or “probable” danger with "relatively certain danger", rather than using an inappropriate opposition between

"potential” and “real” danger” (Brenac, unublished).

The analysis helps to avoid repeating past errors and to give coherence to safety objectives in the implementation of development plans in the broad sense (public spaces, connection between these spaces, taking cyclists and pedestrians into account, etc.).

Territorial study Different types of safety study – Exemples Territorial study

TRANSPORTATION SAFETY IN URBAN AREAS METHODOLOGICAL GUIDE 109 Planning the evaluation

Lastly, the methodology concerning territorial safety studies, in particular as far as defining possible courses of action is concerned, currently requires further study in order to gain more in-depth knowledge. Meanwhile, recourse to assessment criteria, as stated in the information sheet “From objectives to courses of action” helps provide feedback concerning the implementation of actions, in particular those dealing with aspects other than road developments, whose effects are still largely unknown today. Lack of perspective on the subject justifies the evaluations suggested in the information sheets. When used to the full, these information sheets will help to validate the relevance of the actions and to move forward. Research/action would also certainly be advantageous to get things moving.

Mobilising those involved to share knowledge about the issues

Mobilisation and dialogue between the many people involved are dealt with in depth in the works presenting the development of planning projects. Consequently, it is not necessary to develop these issues within the context of this work. If the safety aspect of transport is dealt with, it is included in the management of the various projects.

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Phase 2 - Examples of territorial safety studies

Dans le document Transportation safety in urban areas (Page 109-112)