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Road Design Standards of Medians, Shoulders and Verges

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Road Design Standards of Medians, Shoulders and Verges ANNEX VII to SWOV report Safety effects of road design standards R-94-7 Road design standards of medians, shoulders and verges C.C. Schoon SWOV Institute for Road Safety Research, The Netherlands R-94-7 VII Published by: SWOV Institute for Road Safety Research, Leidschendam, The Netherlands SWOV Institute for Road Safety Research P.O. Box 170 2260 AD Leidschendam The Netherlands Telephone 31703209323 Telefax 31703201261 Notice to the reader This volume is one of the annexes to a main report on safety effects of road design standards which was compiled by SWOV in collaboration with other European partners, in 1993-1994. The project was carried out with financial support of the Commission of the European Union . However, no authority of the European Union has responsability for the contents of this publica­ tion. The main report is a composition of contributions from various authors, edited by SWOV and published in both English and French. The annexes were not re-edited but were published in the form in which they were furnished by the authors. SWOV is not responsible for the contents of annexes that were produced by authors from outside the institute. The full publication consists of the following volumes. Main report: Safety effects of road design standards H.G.J.C.M. Ruyters & M.Slop (ed.); SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex I: Road classification and categorization S.T.M.C. Janssen; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex II: Assumptions used in road design M. Slop; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex m: Methods for investigating the relationship between accidents, road user behaviour and road design standards G. Maycock & I. Summersgill; Transport Research Laboratory, Crowthome, England Annex IV: International organizations and road design standards H.G.J.C.M. Ruyters; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex V: National road design standards H.G.J.C.M. Ruyters; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex VI: Road cross-section L. Michalski; Technical University of Gdansk, Gdansk, Poland Annex VII: Road design standards of medians, shoulders and verges C.C. Schoon; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex Vm: Design features and safety aspects of exit and entry facilities on motorways in the EC (in German) J. Steinbrecher; Aachen, Germany Annex IX(E): Curves on two-lane roads Annex IX(F): Virages sur routes a deux voies (in French) T . Brenac; Institut National de Recherche sur les Transports et leur S6curit6, Salon-de-Provence, France 3 Annex X: "Bicycles at intersections" in the Danish Road Standards L. Herrstedt; Danish Road Directorate. Copenhagen, Denmark Annex XI: Bicycle facilities at intersec oons M.P. Hagenzieker; SWOV Institute for Road Safety Research, Leidschendam, The Netherlands Annex XII: Bibliography Contents 1. Introduction 2. General principles 3. Survey of 0' Cinneide et al. 3.1. General 3.2. Results of O'Cinn6ide et al. 3.2.1. Rural divided motorways (Road category 1) 3.2.2. Rural non-motorway divided roads (Road category 2) 3.2.3. Rural undivided primary roads (Road category 3) 4. Important safety aspects in relation with dimensions 4.1. Basic principle for the design of safe verges 4.2. Safety aspects of road category 1 4.3. Safety aspects of road category 3 5. Consensus and differences between EU-countries 6. Knowledge and research to underpin guidelines References Figures 1-3 Tabel1 5 .6 1. Introduction This report compares the road design standards of medians, shoulders and verges of different road types of EU and EFfA countries. The starting point is the survey conducted within the framework of the European Union DRIVE Programme (O'Cinn6ide, McAuliffe & O'Dwyer, 1993). Fifteen European countries were involved in this project. The results from the report by O'Cinn6ide et al. are reproduced per sec­ tion and provided with commentary (Chapter 3). Subsequently, the design criteria of the countries which have devoted attention to this matter in their guidelines are discussed (Chapter 4). Based on Chapters 3 and 4, the most suitable width of the various cross­ sections is determined and an indication is given in table form of how many countries are able to concur on the basis of their guidelines and how many are unable to do so (Chapter 5). With those parts of the cross-sections where there is minor agreement, proposals for further study are indicated (Chapter 6). 7 2. General principles The design of the cross-section is relevant to: - the prevention of accidents; - the prevention of (serious) injury if a vehicle leaves the road; - the interception of stranded vehicles and the accessibility of an accident location by emergency vehicles. With respect to the prevention of accidents, the correct design of the cross-section can have a favourable influence on driving behaviour. To ascertain this, cross-sections should be uniform in order to be recognizable to the road user. It should be possible to compensate for slight, unintended changes in direction when negotiating the cross-section. There should be a continuity in the cross-section in a longitudinal direction. If discontinuities are nevertheless essential, the transitions must be of a gradual nature. The safe design of the verges is also intended to prevent occupants of vehicles that leave the road from sustaining (serious) injury. This means that a zone with rigid obstacles (but also steep banks and canals) should be situated at a sufficient distance from the road, or that the zone should be shielded by means of a crash barrier. Finally, the cross-section is of importance for the interception of stranded vehicles. It should be ensured that stranded vehicles do not come to a stop on the carriageway and hence create a hazardous situation there, while also obstructing traffic flow. For motorways, it is important that in case of an accident emergency vehicles are able to rapidly reach the accident site via the hard shoulder (emergency lane). The above points represent general principles for the design of the cross­ section. They form the basis for determining the dimensions of the cross­ section. The dimensions are also determined by the vehicle characteristics, where the width and speed of a 'standard vehicle' represent the principal considerations. Although such principles generally are not formulated in the guidelines of the European countries investigated, it must be (implicitly) assumed that these have been used as principles for design. The next step is to allocate the widths applicable to the various parts of the cross ~ection. It should be clear that every country has approached this in its own way, with the cost factor playing an additional role. 8 3. Survey of 0 'Cinneide et al. 3.1. General O'CiiU16ide et al. (1993) have conducted a data collection of dimensions of cross-sections under the European Union DRIVE Programme. Fifteen European countries were involved in this project. In the survey of O'CiiU16ide et al. three categories are distinguished: category 1: rural divided motorways; category 2: rural non-motorway divided roads category 3: rural undivided primary roads. In 5 out of the 15 countries category 2 is not familiar. In this chapter the frequencies of cross-section dimensions of the three road categories are given and discussed separately. The following dimensions of the cross-sections are involved: - median width - lane width - width of the paved iiUler shoulder - width of the paved outer shoulder (emergency lane) - width of the verge (unpaved) N.B. The paved redressing strip between the left lane and the median is missing in the data of O'CiiU16ide et al. 'This part of the road is added to Chapter 5. When gathering data it is important to know whether the data are with or without the presence of crash barriers (guard rails or concrete barriers). In the survey of O'CiiU16ide et al. this distinction is lacking. In the investiga­ tion of the cross-sections of the 15 European countries, it is not always clear whether the data are coiUlected with shielded or with unshielded verges. We shall take this aspect into account 3.2. Results of O'Cinneide et al. In the survey of O'Cinn6ide et al. data of the three road categories men­ tioned before are given in the Tables 12 to 14: 'Standard cross-section dimensions'. The survey contents data of the following countries: Austria Netherlands Denmark Norway Finland Portugal France Spain Germany Sweden Iceland Switzerland Ireland United Kingdom Italy The frequencies of the distinguished parts of the cross-sections in con­ formity with the survey of O'Cinn6ide et al. are given below, with addi­ tional comments. 9 3.2.1. Rural divided motorways (Road category 1) Median width Width (m) Frequency median Frequency width incl. paved unpaved median width shoulders without shoulders 1.0- 2.9 l 4 3.0 - 4.9 3 3 5.0- 7.4 3 2 7.5 - 9.9 2 1 10.0- 12.4 2 3 ;;:: 12.5 4 2 Total 15 15 Many countries have small dimensions of the median width, other have large. It seems that some countries have taken into account the presence of a crash banier, others not A width up to 5 m for the unpaved median is given in the standards of 7 countries; too small for a unshielded median. Six contries have a width of 10 m and more for the median inck1ded the paved shoulders. Lane width Width (m) Frequency 3.5 3 3.65 1 3.75 11 Total 15 Most countries have a lane width of 3.75 m. Data give a good impression of the agreement between the countries.
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