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Review of Safety Measures, Standards & Practices © ARROWS Consortium Project Co-ordinator Prof. George Kanellaidis (NTUA). email: g-kanel@central.ntua.gr ARROWS Objectives The ARROWS Project (Advanced Research on ROad Work Zone Safety Standards in Europe) is funded by the European Commission under the Transport RTD Programme of the 4th Framework Programme. It began on 18 September 1996 under the provisions of Contract No. RO-96-SC.401. The planned duration of the project is two years. The main objectives of ARROWS include:
The present Deliverable 1 reports on the work carried out for Workpackage 1 of the ARROWS Project, titled Review of safety measures, standards and practices. The main objectives of Workpackage 1 were:
The term typology is meant, in the context of ARROWS, to primarily denote a guide to classification. In addition typology is also meant to include:
Conceptual Framework A road work zone may be defined as the part of a road facility influenced by works occurring on, near or above it. Its scope is wider than that of the immediate "work area" actually occupied by the road works, since the control measures used - such as signs, markings and protective devices - extend beyond that area. What is usually thought of as a "typical" road work zone usually relates to roadway and structural improvements, maintenance activities (such as resurfacing), or utility work. However, varying definitions road work zones may or may not include several other types of work carried out on, beside or above the road and influencing the normal flow of traffic. Besides knowing "What" work is carried out and "How", the answers to the questions of "Where" and "When" should be all-important for classifying a road work zone. The proposals envisaged within ARROWS should have European proposals for a harmonized road classification as a reference point, in order to allow ARROWS to contribute to the implementation of the European Common Transport Policy, in terms of systematisation, standarisation and interoperability. The road classification proposed for the TERN, distinguishing between motorways, express roads and ordinary roads, may provide a reference point for the typology to be proposed within ARROWS. For consistency purposes, however, it is important for any framework for road work zone standards to be valid for all roads whether they do or do not form part of the TERN. In addition, the ownership/operation status of the road facility should not affect applicability of recommendations. The main considerations for building a typology included: its intended use as a tool for classifying and organizing subsequent review, analysis and, especially, the ARROWS output; the need for reaching a "proper" balance, by avoiding being over-simplifying, too case-specific, or too theoretical; its possible structure. Classification Factors Main classification factors can be grouped into the following categories: (a) road type, design, function and operation; (b) operation of work zone; (c) interaction between work zone and roadway. The commonest classification factors identified in a review of European and other guidelines include: the distinction between urban and rural roads (with special mention of motorways); speed (at-work zone or upstream) and traffic volume / capacity; stationary vs. mobile; long-term vs. short-term; effects of work zones on traffic, such as narrowing, closure, diversion, contraflow, alternate traffic; special locations such as intersections / interchanges and certain off-roadway locations (shoulder, roadside, central reserve, footway or bikeway). Selection of Typology The basic requirements for selecting a typology included compatibility, comprehensiveness, clarity and flexibility. The selected typology features three classificication factors: road type, operation of work zone and road/work zone interaction.
Five categories regarding road type were defined:
In general, varying national definitions of road classes can be adequately accommodated under this broad classification of road types.
Three categories were defined regarding work zone operation:
The following categories were defined regarding road/work zone interaction:
(a) Lane narrowing (without reduction in the number of lanes; lane width should not fall below an acceptable lower limit)
(b) Lane closure (relevant only on multi-lane roads) (c) Diversion (transferring all or part of the traffic from one road - "diverted road" - to another - "diversion route") (d) Contraflow / crossover (transferring all or part of the traffic to the other carriageway or to occupy lanes from the opposite direction) (e) Alternate one-way traffic (where only one lane remains available for the two directions of travel) (f) Intersection / interchange (the latter term is used to denote entrance to or exit from a motorway or dual-carriageway expressway) (g) Shoulder / roadside (h) Central reserve (i) Footway / bikeway (j) Tramway The choice of road work zone type will be denoted by a three-character abbreviation, signifying road, operation and location. For example, a long-term work zone on a motorway involving contraflow is shown as A-1-d. Safety measures are split into two main groups:
In each group, and taking into account the road work zone typology a survey has been undertaken for the following categories of items:
In the signing field, "normal" (i.e., non-work zone) signs, as currently used in the EU countries, are additionally reviewed, in order to specify the colours actually used, as an aid for selecting such colours for road work zone signing that will not be confused with permanent road signing. Moreover, the evolution in the form and usage of the various safety measures/products is recorded in detail and, regarding the innovative measures, improvements (proven or expected) in comparison to current safety measures are emphasized. Finally, recent suggestions regarding the need for further research or improvements in the field have been identified and highlighted. Adjustment of Road Layout The following sections were identified for individual examination of road layout adjustment along a road work zone
In case the carriageway consists of two or more traffic lanes, some additional road sections are defined:
Following the typology, the following are the main remarks to be made on currently-used road layout adjustments for various road work zone types:
It was not possible for the ARROWS consortium to identify innovative items on road layout adjustment, for the following main reasons:
Traffic Control Devices Currently used items in traffic control devices include the following:
Regarding the above items, particularly interesting areas for further consideration in ARROWS include:
Innovative items in traffic control devices include:
Regarding the subsequent consideration of the above items within ARROWS, the following remarks can be made:
Other Road Equipment Currently used items on other road equipment include:
Some selected innovative devices include "two signs in one"; "UV-light"; supervision devices; cart for fold-up cassette signs; emergency cart; crash net - vehicle sustaining barrier; crash cushion - truck tyres; crash barriers; portable rumble strip; and warning tent. Miscellaneous Items Currently used miscellaneous items include:
Innovative miscellaneous items concern mainly:
REVIEW OF STANDARDS AND PRACTICES Review of Standards Complete polling of all European countries has shown that in 16 of 20 countries there are standards, directives, recommendations or similar sets of regulations which regulate the traffic guidance systems used in the region of work zones in terms of their type, extent and road equipment to different degrees. The fundamental intention was to base the following analysis on the classification points from Task 1.1. However more detailed consideration showed that it was necessary to take into account further viewpoints in order to permit the envisaged comparative evaluation to be carried out. As a result an expanded classification scheme was used for Task 1.3 (identifying differences from Typology as "additional information"):
Finally, nine additional items refer to the subdivision of the work zone area in the longitudinal direction; the areas identified include: (7) announcement; (8) advance warning; (9) narrowing; (10) stabilizing; (11) transition; (12) buffer; (13) activity; (14) termination; (15) run-off. Fundamental evaluation results include the following:
A comparative review of traffic signing used for this guidance system reveals that only few different signs are used, but on various positions and with different mass. This illustration shows a possible way for creating a harmonized framework for diverse work zone areas for all situations. Review of Implementation of Road Work Zone Standards Regulations, guidelines, standards and recommendations give fundamental or detailed information for the designing and setting up of such work zones in accordance with traffic flow principles. As a rule such sets of regulations are to be found primarily for the roads with the highest volume, i.e. motorways. In the securing of work zones on or in the vicinity of roads, the maintenance of safety and of the free flow of traffic are always in the foreground. In addition to traffic signs, speed limits are often made use of for this purpose. In addition, protecting devices between lanes of traffic flowing in opposite directions are being used to an increasing extent in particular on motorways. Noticeable in more recent regulations is the fact that increasing attention is being paid in addition to the safety of those working in the work zone and that safety devices located between the traffic lanes and the area for work are being used to a greater extent. Worthy of mention in this connection are recommendations on buffer zones at the beginning of the work zone in which there should be no equipment and in which no one should work. The following main aspects can be identified in the guidelines:
In order that as many as possible of these aspects can be observed, it is laid down in most countries that a plan with the traffic signs as well as the marking and safeguarding systems is prepared before work is commenced. Depending on the particular legal requirements, such plans must be checked, corrected if necessary and then prescribed for the work by in each case the responsible, official authority. Especially in the U.K., the preparation and local adaptation of safety measures is always carried out by a fundamentally competent supervisor whereby the safety measures must be additionally checked by the responsible authority in cases where a work zone will disrupt traffic to a considerable degree. Less useful, on the other hand, are framework regulations which should be followed by local experts with a greater or lesser degree of competence and where the measures are not additionally checked in a qualified manner. Unfortunately, in a number of plans for the safeguarding of work zones, the principle "the more the better" has been followed. To be particularly mentioned in this connection is excessive use of blinking and flashing lights. In some cases the synchronizing of such lamps is required. Nevertheless priority should be given to the fundamental principle that a traffic situation, which will be unexpected and unusual for the majority of drivers, should be designed in a quiet and easily overviewed manner, instead of in a manner that - through the introduction of additional distractions - will impair drivers' abilities to master the particular situation. Comparison of Practices Among Countries Generally the aims of regulations, guidelines, etc. give the minimum needed signalisation on a road work zone to inform, give the way and guide road users through the work zone with:
The person responsible for the safety of a work zone must be prepared to think about the individual problem and be prepared to make available what is optimally required for the drivers and other travellers; unfortunately, practical experience shows that this will only be achieved when appropriately strict checks are carried out and appropriate sanctions threatened. Obviously, the promotion of measures to ensure that the relevant contractors understand the safety aspects and feel responsible for these is an important task in connection with work zones on motorways and other roads. Some common advice (Belgium and Germany) is presented:
There are great shortcomings in the area of checking of work zones, despite relevant requirements in the regulations. Prime causes here are bottlenecks in the personnel in the different monitoring posts. As a rule the contractor is then usually found to be responsible, although the avoidance of such situations by early and intensive checks would have been more sensible. In conclusion it can be established that - in addition to the optimizing of traffic sign, marking and safeguarding plans - increased efforts must be made to creating the fundamentals for the training of contractors. More guidelines and less checks will only be effective when an appropriate level of understanding and co-operation can be expected from the side of the contractors. Here, however, no secret should be made of the fact that - if work zones are to be safeguarded in the optimal manner - the work involved must be appropriately paid for. |