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Road Work Zone Safety Practical Handbook

Contents



© ARROWS Consortium

Project Co-ordinator Prof. George Kanellaidis (NTUA). email: g-kanel@central.ntua.gr


VOLUME I

Summary

The ARROWS handbook, aimed at improving the safety of road users and workers at road work zones, is intended for highway authorities, designers, contractors and other individuals and organizations responsible for traffic safety at roadworks. It is a product of the ARROWS research project, funded by the European Commission.

The handbook is a pre-normative framework of recommendations - i.e., it is not intended to replace or supersede existing national official standards. The main focus of the handbook is the introduction of a common "best practice" for road work zone design and operation.

The handbook features detailed examples of the most commonly encountered work zone cases, with recommendations on the selection and placement of safety measures. The recommended values are proposed on the basis of the following criteria:

  • firstly, to ensure a high level of safety;
  • secondly, to harmonize between the standards of European countries - provided that the first criterion is not violated.


In addition, the handbook presents principles, procedures, tips and checklists for the safe implementation of work zones. The general recommendations given in the handbook can be useful in the implementation of road work zone cases that are not covered by a specific detailed example, either in national standards or in this handbook.

Moreover, the handbook's recommendations may be used as a starting point for the development, modification and/or amplification of national guidelines. This could be especially useful for countries whose road work zone safety standards cover only a specific type of road (e.g. motorways) - or only a small number of work zone cases.

When applying this handbook, the user must take not to violate either national legal requirements or international conventions/agreements. The handbook presents recommendations on the safety measures to be used at different work zone types, as well as on the procedures and responsibilities in the process of implementing a road work zone. Even though the recommendations are largely the result of harmonization between European national standards, they are not "normative" or "legislative".

In many cases the recommendations will differ from the national standards for road work zone safety in European countries. Moreover, the handbook should be consulted in cases where procedures and responsibilities are not adequately defined in national standards. National authorities are advised to take into account the handbook's recommendations in the process of revising their standards.

The handbook includes:

  • A description of road work zone safety objectives and principles
  • An outline of procedures and responsibilities for all stages of road work zone implementation
  • Practical recommendations in the form of "safety tips"
  • An illustrated glossary of safety measures
  • Recommended layouts for the most common road work zone types
  • Indicative checklists

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Volume II

INTRODUCTION

The present Deliverable 4 - Volume II reports on the work carried out within ARROWS Workpackage 4 (Practical Handbook). It constitutes a Background Report to the ARROWS Practical Handbook, which is produced as Deliverable 4 - Volume I. The Workpackage consisted of the following Tasks:

  • Task 4.1 - Safety Principles. The initial objective of this Task was to propose a set of safety principles for the proper planning, design, implementation, operation and follow-up/assessment of road work zones across Europe. This is reported in Chapter 1 of the present volume. During the course of the project, the subtask of Accident Scenario Construction was added to this Task, with the objective to complement the conclusions from behavioural and accident studies through analysis of expert-generated data on "virtual work zone accidents". The procedure and results are reported in Chapter 2 of the present volume. Furthermore, Appendices 1 through 9 present detailed information about the accident scenario pilot study's inputs and outputs.
  • Task 4.2 - Recommendations and Compatibility. The objective of this Task was to formulate recommendations of sets of measures (layout, traffic control devices, other road equipment, and other measures) for all types of road work zone, as well as to determine possibilities for harmonisation of national guidelines and compatibility with relevant European agreements (such as TERN, CEN, and TEM). The work carried out for this Task is reported in Chapter 3 of the present volume.
  • Task 4.3 - Practical Handbook. The practical handbook is the key output of ARROWS and constitutes Volume I of this Deliverable. Itemisation of the cases selected as layout examples, as well as identification of safety issues - including "tips" and "checklists" - was largely based on the material of Tasks 4.1 and 4.2. Moreover, recommendations for the road worker are presented in Annex I to this volume, and a discussion of issues related to the management of road work zones appears in Annex II to this volume.

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CHAPTER 1

Chapter 1 is a compilation of safety principles, derived from the work which has been conducted in the ARROWS project, which can be used for the planning, design, implementation and operation European road work zones.

This compilation is primarily based on the compiled and original findings of previous phases of the ARROWS project. To this end, each of the involved partners was asked to prepare a contribution, based on a specific ARROWS Task report. Those sub-task assignments were:

  • Typology (CROW)
  • Measures (3M)
  • Standards and Practices (BAST)
  • Behaviour (BAST)
  • Accidents (3M)
  • Methods (3M)
  • Synthesis of Improved Sets of Countermeasures (3M).


All partners were also encouraged to freely contribute as they saw fit. The possibility of incorporating existing guidelines from each partner's country was also stimulated.

The idea was that, to the extent that previous ARROWS work was systematic, complete, and unambiguous, then (some) principles should be extractable in a structured way. To the extent that these conditions did not obtain, then less structured contributions could also be useful.

Even though there are (some) gaps, ambiguities and overlap between principles, every principle and/or argument mentioned in this paper can be profitably considered.

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CHAPTER 2

Chapter 2 deals with accident scenario construction. The ARROWS consortium is interested in gathering and organising scientific knowledge concerning work zone traffic accidents, in order to produce suggestions for pan-European guidelines for implementing work zones. One effort to that end was not as illuminating as originally hoped, due to limitations in the scientific literature. In addition, there were no funds available for gathering data from actual work zone accidents, nor for analysing the data that already exists in (inter-)national databases.

To cover this lack, it was suggested that if we had no access to actual accidents then it might be useful to extract the intuitions of the ARROWS consortium about work zone traffic accidents. To this end, we asked these experts to consider virtual accidents, which we further treated as if they were real.

It was also the intention to include experts form outside the consortium, who represented other groups of stakeholders in the area of work zone safety: policy makers, police officials, contractors, etc.

This could have allowed a broader view of the problem area, contributed to the overall acceptance of the consortium's efforts, provided a common forum for a pan-European discussion of the subject, and allowed for comparisons of differences and similarities between viewpoints.

Due to a number of limitations, a more modest pilot study was conceived, which would make use of a session of the ARROWS Workshop in Athens in 1997 as the kickoff. This author prepared six discussion papers, which were to presented to six parallel working groups of 5 workshop participants each . Each group attempted (by means of a brain-storming procedure) to consider possible answers to central questions poised in the discussion papers.

The results of these working groups were then combined with existing accident forms, information found in previous ARROWS deliverables, and other relevant sources of information, to produce a "virtual" work zone traffic accident registration form. Eight copies of said form were sent to all participants of the Athens Workshop with the request to consider a concrete work zone traffic accident (either real or imagined) and to fill in an accident form in order to describe that accident. This was done for a total of eight times. 5 times subjects were given a road type of which the said accident had to occur, 3 times the subjects could freely determine the road type themselves.

About 2/3 of the subjects responded, and their returned accident registration forms were entered into the computer and analysed by means of non-linear Principal Component Analysis.

This process has resulted in very simple and clear results. Namely, the variability in the characteristics of work zone traffic accidents, as studied in the present report, can be reduced to three underlying, basic dimensions:

  • the type of road on which the work zone is located, with motorways being contrasted with urban local roads;
  • the duration of the work zone, varying from short-term and ad hoc to long-term and more-extensively organised.
  • the time-of-day cycle. It is only this last dimension which is clearly associated with different types of accidents.


These results may then be used as starting points for developing checklists and guidelines, which may then be incorporated in a practical handbook.

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CHAPTER 3

Chapter 3 deals with recommendations and compatibility. Before planning of work zone and before decision of the technique of ensuring the concrete work zone the designer should collect as much as possible information about planning activities on roads (e.g. detailed description of appropriate road segment, range of planned work zone, current traffic signs and devices on this road segment, possibly supposed diversion and its length and direction and contingently order of phases of traffic lights).

The design of work zone measures should follow possible stages of activities, its possible combinations, types and duration.

It is evident that the different level of work zone ensuring (measures) will be designed for appropriate type of work zone. Therefore during the planning phase is necessary respect the location of work zone i.e. on urban roads (main, local), on rural roads (primary, secondary) and on motorways or expressways, farther its duration - long-term or short-term (stationary and mobile) - only during day light, and also take heed to possible concurrence of works.

If the ensuring of work zone with short term duration shows as insufficient from the point of view of road safety (i.e. gross fog or rain, snow etc.), it is necessary to use the same purpose of measures as on work zone with long term duration.

The purpose of ensuring of concrete work zone should come out from the appropriate model traffic scheme mentioned in practical handbook.

The form of work zone ensuring is necessary to decide on the base of local conditions (partial or complete road enclosure, diversion). The basic principle is to keep as far as possible the same number of lines on road or to find the traffic solution, which makes possible to keep traffic in both directions.

In case there is only one line in the work place area for both traffic directions it is necessary to decide on the basis of a local situation and traffic intensity whether it is possible to lead traffic on the basis of the intermittent traffic, with help of traffic signal or to set up a diversion. It is also possible to use the both way combination (for instance to set up diversion for particular vehicles, particular time or for one traffic direction only).

If the traffic intensity is too high and there is no possibility to set up diversion it is necessary to think of making provisional diversion road in the work area.

In the case of partial or complete road enclosure is necessary to consider the ensuring of cyclist and pedestrians, too. In the case of works on foot-paths or on cycle tracks is necessary to provide alternate and safe way of transportation for this vulnerable traffic participants.

Complete road enclosure for all kinds or same kinds of traffic is a big interference with organisation of traffic, because it means to set up a diversion.

In case a diversion road is used for longer time it is good to sign it up as a main road particularly if the traffic on important and busy road is turn away. Except interference into a giving way rule changes there may be also an importance of temporally speed decrease limit in area, which is unsuitable for temporally increase traffic. A diversion must be signed by traffic signs in advance for all drivers to make possible to get use to those traffic changes. It is useful to inform about a diversion in media.

Some main aspects for installing work zones are:

  • Choose time and duration of work zones in correspondence to traffic requirements and volume.
  • Adhere the number of lanes as far as possible.
  • Govern the design of the work zone (alignment, lane width and length).
  • Determine uniform layouts with signs as few as possible but as many as necessary.
  • Make work zones consistent during working and cancel them after the work is finished.
  • Use high quality materials for signing and marking.
  • Maintain traffic signs, markings and safety devices in a proper form all the time.
  • Train personnel in regard to their responsibility and their own safety aspects.

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