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1 Information Note ^ìíüçêë=w=p íê~= `bqb=çé=ädbëí= `bqb=kçêã~åçáéj`éåíêé = åçîéãäéê=ommv= íê~åëä~íéç=ã~ó=omnn = _~íë=~åç=êç~ç=íê~åëéçêí== áåñê~ëíêìåíìêé= qüêé~íë=~åç=éêéëéêî~íáçå=ãé~ëìêéë= båçåçãáåë= båîáêçåãéåí= aéëáöå= VN= Metropolitan France is home to 34 species of bat. They are all protected at national and international level (Bonn and Berne Conventions, EUROBATS Agreement, species of community interest). Bats are the only mammals that are able to fly and they constitute a particularly remarkable group of species many of which are currently endangered. The main factors responsible for their decline are no doubt the destruction and modification of habitats. Although collisions involving transport infrastructure are the factor with the most visible impact on bats, habitat fragmentation probably also has major impacts on bat populations. In response to the need to implement conservation measures for the species present in France, a national bat restoration plan was launched in 2007 for the period In the framework of this plan, Sétra has been asked to take stock of the available knowledge about bats and transport infrastructure, and, based on this survey and the monitoring of sites where collisions have occurred and systems that are designed to reduce such impacts, to propose technical recommendations for road designers in order to ensure that projects take account of bats. This information note presents the principal elements of the first phase on the survey of existing knowledge about bats and linear infrastructure. It summarizes the information obtained in the course of our analysis of the national French and international literature and meetings with French subject experts [1]. Contents 1. About bats Protected endangered species Measures to take account of the bats in infrastructure Current and future knowledge...17 Appendix...21

2 Sétra Information notes Economics Environment Design Serie n About bats Bats, which are the only mammals that are capable of true flight, are distinctive in that they possess genuine membranous wings. Thirty-four species, belonging to four families, are currently found in France, and they are all protected (see the list of protected species and protection status in the Appendix). Bats: a brief description Common name Scientific name (a few species) Class Order Families Bats (see the list of the common name of each species in the Appendix) Greater horseshoe bat (Rhinolophus ferrumequinum), Daubenton s bat (Myotis daubentonii), Greater mouse-eared bat (Myotis myotis), Soprano pipistrelle (Pipistrellus pygmaeus), Brown long-eared bat (Plecotus auritus), European free-tailed bat (Tadarida teniotis), (see the complete list of scientific names in the Appendix) Mammals Chiroptera Horseshoe bats, Long-winged bats, Vesper bats, Free-tailed bats Code Natura 2000 Protection status: International Community Mehely s horseshoe bat (Rhinolophus mehelyi): 3 sites Lesser horseshoe bat (Rhinolophus hipposideros): 424 sites Greater horseshoe bat (Rhinolophus ferrumequinum): 453 sites Mediterranean horseshoe bat (Rhinolophus euryale): 120 sites Lesser mouse-eared bat (Myotis blythii): 142 sites Barbastelle bat (Barbastella barbastellus): 263 sites Common bent-wing bat (Miniopterus schreibersii): 176 sites Long-fingered bat (Myotis capaccinii): 48 sites Pond bat (Myotis dasycneme): 7 sites Geoffroy s bat (Myotis emarginatus): 337 sites Bechstein s bat (Myotis bechsteinii): 226 sites Greater mouse-eared bat (Myotis myotis): 432 sites Bonn convention: Appendix II Bern convention: Appendix II and III Habitats and Species Directive: Appendix II and IV Photo: Greater mouse-eared bat (L. Arthur, MHN Bourges) National Ministerial decree of 23 April 2007 Description: Morphology Size and weight Bats are the only mammals that can fly and they have a very thin light wing membrane that stretches from their flank to their arms and hands and joins their fingers to their rear legs and tail. This varies in size according to the species. Their clawed feet lock in a sheath allowing them to hang upside down. They have a very hairy body and the teeth of an insectivoran. The form of the head differs across species: the ears can vary in length (between 9 and 40 mm); the size and shape of their auricle and snout also vary a great deal. In some species the nose is horseshoe shaped (greater horseshoe bat, lesser horseshoe bat), and their eyes are generally small. The different species vary in size between 20 and 50 cm and weigh between 4.5 and 50 g. Common pipistrelles are extremely small, measuring only between 3 and 5 cm. Lifespan Relatively long, between 5 years to more than 40.

3 Sétra Information notes Economics Environment Design Serie n 91 3 An annual biological cycle Bats have a number of characteristics, which include the ability to hibernate in the cold season. This is because insects are scarce in winter so there is likely to be a shortage of food. Bats therefore return to their roost and live at a lower rate (hypothermia, lower heart rate), and draw on the reserves they have built up in the other three seasons of the year. At the end of winter, they leave their winter roosts and move to their summer roosting sites. A specific characteristic of this group of mammals is that during the summer months the males are generally solitary, living apart from the females in separate roosts. Females move to separate roosting sites in order to give birth. When the young are born and how long they are fed depends on the species (from May to July). A sign of their limited energy budget is that every year females produce only one, or exceptionally two, pups. During this period, the females need to hunt intensely and generally return to the roost several times a night to feed their young. Figure 1: the cycle of activities and roost changes At the end of the summer, the young gradually learn to fly. Initially they fly with their mother, travelling further and further from the roost as their flight improves until they disperse in the autumn. Unlike the majority of French mammals, male and female bats share breeding roosts in the autumn in order to mate before gradually returning to their hibernation roosts. Female gestation is temporarily halted, by delaying fertilization (storage of sperm) or by halting the development of the embryo until the next spring. A living area that has three principal components While the presence of bats is frequently associated just with a winter or summer roost, bats have large territories, which are occasionally at some distance from their resting zone. Their living area has three principal components: roosts These are of several types: hibernation roosts: in winter, bats seek out areas with low constant temperatures, where the air is almost saturated; and which are quiet before entering into a long period of lethargy. Although some species may use bridges (gaps, drains), cavities in trees (woodland species) or attics, most bats usually spend the winter in caves, mine shafts, military forts or cellars; summer roosts: in summer, bats look for roosts that are fairly warm, in particular in order to give birth and raise their young. Suitable sites include underground locations (mines, caves, tunnels), roofs, belfries, cracks in walls, behind shutters, cavities in trees, under bark, in woodpiles, under bridges, or in flue liners; transit roosts: in the course of the year, particularly during migration between winter and summer roosts, bats may rest in transit roosts in much the same way as migrating birds (some species of Noctule or Nathusius s pipistrelle can travel 1,000 or even 2,000 km); mating roosts (or swarming roosts): are the roosts were males and females group together in order to mate.

4 Sétra Information notes Economics Environment Design Serie n 91 4 movement corridors When they travel between different roosts or in order to go foraging, the flyways used by bats usually consist of linear landscape structures. Thus, they generally follow lines formed by bushes and trees, hedges, watercourses, walls, fences, the edges of forests, ditches and even sometimes roads. Foraging areas may be at some distance from the roost and the daily distance covered varies according to the species and the local environment (5 to 10, or even 30 km from the roost). foraging areas Deciduous forests, pastured fields and wetlands with a wealth of insect life are the favoured foraging areas for bats. They generally tend to avoid zones of cereal monoculture. Pipistrelles, serotines and long-winged bats nevertheless take advantage of locations where insects are attracted to urban lighting in order to feed. A diet which is of prime ecological importance In spite of the fact that the different species have very different ecological requirements, all French bats are predominantly insectivorous. Their ability to consume up to 800 insects in the course of a single night s foraging means they play a vital role in controlling insect populations in ecosystems and are an ally in the fight against insect pests. Nocturnal activity One of the characteristics of this group of mammals is linked to the fact that they are active at night. They have developed a mode of nocturnal travel and foraging that relies on echolocation (by emitting ultrasounds). This system means they can fly and target their prey in complete darkness. Each species emits specific frequencies of ultrasounds, which in most cases, can be used to identify it. 2. Protected endangered species The bat restoration plan Bats are a threatened group of species some of which have experienced a particularly alarming decline in numbers. As a result of this vulnerability all French bat species are protected at national, European and international level. France also wished to put in place a more comprehensive strategy for bat conservation and protection via a programme of targeted measures. The "restoration plan for bats in metropolitan France" was thus drafted for the period and includes a series of measures that aim to maintain the population in a favourable state of conservation. Twenty-six measures that were listed and ranked according to their level of priority were thus laid down to meet the challenges faced in France. This plan followed on from an initial process that ran from that was part of a more general European programme based on an international agreement on bats entered into by France (EUROBATS) [33]. Two of the measures of the current restoration plan are specifically concerned with infrastructure and are coordinated by SETRA: the development and implementation of a methodology in order to consider bats during the construction and maintenance of infrastucture and other engineering structures (measure No.6 in the plan); an appraisal of the effectiveness of systems aimed at reducing the impact of transport infrastructure (action 7 in the plan).

5 Sétra Information notes Economics Environment Design Serie n 91 5 The threats This group of species faces a very large number of threats, of which disruption caused by humans is without any doubt the greatest. These threats include not only the destruction of roosts, the modification of habitats but also disturbance, the use of pesticides and toxic products, collisions with road vehicles and mortality caused by wind farms. Our lack of knowledge about bat population dynamics, the difficulty of studying them and the wide range of habitats they frequent however make it problematic to rank the threats they face in a precise order. The disappearance or modification of roosts and the transformation of their living areas nevertheless appear to be the two main threats facing bats. Transport infrastructure, one of the causes of mortality In spite of our imperfect knowledge about the impact of a given piece of transport infrastructure on bats, in particular due to the difficulties involved in studying this group of animals (they are nocturnal, they move in three dimensions, different species behave in very different ways), it is nevertheless apparent that the impacts of the construction of transport infrastructure are mainly the result of three principal factors: the destruction of foraging areas, the destruction of flyways, and collisions. By destroying roosts, habitats and flyways By directly destroying roosts, clearance activities and earthworks within the right of way are probably the phases of construction that cause the most harm to the resting, rearing and reproduction habitats of bats (underground roosts, trees, buildings, etc.) [2, 3, 4, 5]. The level of impacts nevertheless varies a great deal according to the period at which these works are conducted. Thus, the periods when the young are being reared or adults are wintering are particularly sensitive as individuals are unable to escape [3]. In the same way, the destruction of natural environments such as forests, wetlands, hedged farmland or uncultivated land in the right of way or in order to facilitate the works (tracks, stockpile areas) can lead to the destruction of foraging areas and/or create very large new areas of open land that can constitute physical barriers preventing the movement of bats [4, 6, 12, 13]. Last, earthworks or changes in working practices generated by the project (intensification of farming activities due to land consolidation) may also lead to the destruction of structures in the landscape that are used by bats as flyways. A break, even a few metres long, in the linear structures that form flyways is likely to reduce or prevent access to foraging areas or more remote roosts [6, 31]. By collision with traffic Although it is difficult to estimate, direct destruction of bats by collision with a vehicle would appear to be the most visible effect. For bats that fly along structures in the landscape (hedges, lines of trees, edges of woodland, etc.) and, for some lowflying species, the intersection between these landscape structures and infrastructure creates genuine blackspots. References of the study Type of road Duration (month) Observations (number) Km Bodies (number) Species (number) Capo et al. (2006) [7] Ring road Vaine (2005) [8] Motorway Néri-ENMP (2004) [9] Motorway Lemaire and Arthur (1998) [10] Trunk road , Girons (1981) [11] Trunk road Table 1: mortality data from the French literature Source: [1]

6 Sétra Information notes Economics Environment Design Serie n 91 6 The findings of bat collision mortality studies are fairly variable, with mortality rates varying between 1 and 30% [12, 2, 13, 10]. In fact, it would seem that the number collisions and the affected species depend on a number of factors: the period and age of the individuals There are two peaks in collision mortality, during May and during August and September, when bats travel a great deal. During the first period bats have just come out of hibernation and need to feed a great deal, and during the second they need to build up their reserves before hibernating again [2, 9, 14, 15, 13]. The end of summer and the beginning of autumn also corresponds to the period of natal dispersal. Inexperienced juveniles seem particularly vulnerable. Accidents are therefore particularly common near maternity roosts. a specific type of flight for each species [15, 10] Although all species are potentially vulnerable, horseshoe bats and long-eared bats are probably the most affected by collisions. It would appear that their short-range sonar often leads them to fly at low heights and cross roads near ground level. The other species that are the most frequently affected are pipistrelles (the common pipistrelle and anthropophilic species), long-eared bats, Daubenton s bat, the whiskered bat and Natterer s bat. Noctules and Serotines generally fly at greater heights. the longitudinal profile of the infrastructure [16] The impact seems to be greater when the infrastructure is on an embankment as the bats are forced to fly higher and tend to fly at a height near that of the structure and therefore vehicles. the characteristics of the infrastructure the density and the speed of road traffic The collision mortality rate varies according to the speed and density of the traffic [12]. Continuous traffic seems to be more dissuasive than isolated vehicles and the faster the vehicle is travelling the less able the bat is to avoid it. In order of decreasing danger, we therefore have: fast isolated vehicles > fast dense traffic > slow isolated vehicles > slow dense traffic. + dangerous - dangerous Fast isolated vehicles Fast dense traffic Slow isolated vehicles Slow dense traffic Small roads with low traffic also seem extremely deadly. Some experts even state that small hedge-lined roads are more deadly than motorways for bats. As the level of traffic is low and there are plants, they are attractive for foraging while bats keep away from dense traffic because of the noise and light. bad weather [10] Bad weather also seems to have an effect, reducing the number of accidents. vehicle category Because of the large number of night journeys they make, their size and the turbulence they generate which draws in bats, trucks seem to be the vehicles responsible for most collisions [2, 17, 13, 14].

7 Sétra Information notes Economics Environment Design Serie n 91 7 By disturbance Although the sensitivity of bats to light varies somewhat from species to species, they seem to avoid it systematically when not foraging [2]. Bats seem to make use of unlit areas around roads in order to cross them. Some species seem to avoid light more than others (in particular, long-eared bats and horseshoe bats). Road lighting and headlights can also act as visual barriers for these species [13, 18]. During foraging periods, other species such as serotines and pipistrelles nevertheless take advantage of streetlights in order to hunt the insects that are attracted by the light they give out. The impacts of noise and vibrations from a road are more difficult to assess but supplement those of light. The most affected species are those that hunt by ear, by direct audition (for example the greater mouse-eared bat). As they are nocturnal, during works bats are potentially only affected by nighttime activities. Light, odours and noise generated by the works can also delay or discourage bats from leaving their roosts, or even in certain cases, lead them to abandon a site. As is the case with earthworks, disturbance of this type can also create a barrier that prevents species from moving and lead to the loss of a customary foraging area. Construction activities can also lead to some indirect disturbances. One example is when a project improves the accessibility of roosts to the public who then disturb the bats [18, 19]. During the maintenance and modification of existing infrastructure The repair and maintenance of structures by strengthening, the filling of hollows (manually or by spraying), pouring concrete into empty spaces imprison bats and lead to their death. Works of this type are also likely to create noise pollution and vibrations in addition to modifying the thermal conditions and humidity in the roosts [2, 20, 27]. The combination of these factors can create adverse conditions that lead the population to move. Occasional positive impacts The principal beneficial impact of a piece of infrastructure is due to the fact that it involves the construction of a large number of structures some of which provide very suitable roosts for bats: the spaces between the cornice and slab, gaps, expansion joints, drains, the inner surface of arch stones, etc. [20, 23] Figure 2: examples of features that are suitable for bat roosts: the free space between the cornice and the bridge deck (on the left), the gap between two stone blocks (on the right) - Source: Sétra [30]

8 Sétra Information notes Economics Environment Design Serie n Measures to take account of the bats in infrastructure The following sections set out the variety of measures that are proposed in the national and, in particular, international literature. These measures are described for information only and do not constitute recommendations that are directly applicable in France. This is because the implementations of certain foreign practices may be incompatible with French national constraints, in particular as regards aesthetics and road user safety. All the constraints must therefore be considered before any measure is implemented. The different ways bats can be taken into account in construction or modification projects A survey of knowledge and the organization of inventories Whatever the type of project and the level of study, it is essential to conduct a preliminary literature search. In some cases, this is sufficient, in particular in the case of preliminary studies. Data of two types must be collected in order to assess the potential the zone in question has for bats: local bat data (species, presence of roosts in the surrounding areas (10-15 km)) and the types of habitats (mapping). Based on this preliminary analysis, and in particular depending on the amount of available data on the zone, the type of project, the habitats that it crosses and the importance of the issues (priority species or outstanding sites), the project owner can conduct a valid evaluation of the level of the additional field studies that are required. The organization of these inventories should therefore identify the three major types of location their environment must provide for bats, namely roosts, flyways and foraging areas. A satisfactory inventory often takes a minimum of one year to perform. The search for roosts At this stage, and in the framework of a preliminary study, the search is conducted 1 km on either side of the route of the road, which may be increased to 3 km, or even more if particularly sensitive species are present [21]. Although it is frequently possible to find out about the presence and location of the major bat roosts by conducting a literature search, it is often necessary to look for favourable roosts in the field. The search for winter roosts and summer roosts is given priority, which means it is usually necessary to conduct investigations during the summer (the best time being between May and September) and during hibernation (the best period being between November and February). As bats are likely to visit a large range of habitats (depending on their ecological characteristics, the available habitats and the season), it will be necessary to conduct the search in various types of potentially favourable environments: ancient deciduous forests (tree roosts), old farms, military structures, bridges, churches, barns, country homes, castles, karstic environments or areas with a large number of underground spaces (cavities, mines, tunnels, caves and pits), etc. [18, 21, 13, 22, 3, 23, 24]. When the presence of bats is observed in the study area and their roosts are unknown, a variety of techniques can be used to discover their cavities (See Table 2): searching for roosts by following the different stages of bat journeys (this requires several surveyors) in zones which they may potentially use a great deal (corridors, linear structures, etc.) [18, 24]; radiotracking: after a bat has been caught in flight and fitted with a transmitter, individuals are followed to their roosts by radiotracking. This method is very effective but relatively costly and disrupting for the animals [24].

9 Sétra Information notes Economics Environment Design Serie n 91 9 Identifying foraging areas and flyways This stage usually follows from a preliminary landscape analysis, based in particular on aerial photographs, the location of roosts and a field visit to identify the landscape features which are potentially favourable to the presence or transit of bats: mature forests, large hedges and small fields, areas with a high proportion of pasture, the presence of areas of water and watercourses (rivers, canals, lakes, pools, reservoirs, wetlands, ponds, wet grasslands, etc.) Once the favourable zones have been identified, a study of bat activity in these areas is conducted in order to validate or refute the initial analysis. Several methods are used to conduct this study of bat activity (see Table 2). Measures in order to remove, mitigate or compensate for impacts While bat conservation primarily requires the conservation of their habitats (wet valleys, grassland, forests, hedgerows, underground environments, etc.), a large number of measures are now available to overcome the local impacts of a piece of infrastructure. Taking account of bats in construction projects is, however, fairly recent. In addition, most current proposals are still very often merely recommendations, which so far have been too rarely applied. Nevertheless, the majority of authors stress that the measures proposed below must be put in place before roosts, foraging areas or flyways are destroyed [6, 18]. Measures to remove or avoid impacts Bat conservation first of all requires the conservation of existing environments and structures that are favourable to the different species [6, 18, 21, 12]. To do this, it is necessary to conduct studies that are as comprehensive as possible and select a route, which as far as possible avoids destroying or disrupting roosts, flyways and foraging areas. Maintaining landscape structures Very often, in order facilitate the manoeuvres of worksite machinery, a few hedges, trees and other structures are destroyed. To avoid the accidental destruction of structures that are essential for bats (hedges, roosts) these may be marked on the site (flags, fences, tags, etc.) [6, 13]. It is also recommended for works to be monitored by an environmental officer. Limiting the attractiveness of roadside vegetation The location of roadside vegetation and other structures that are likely to attract bats, such as highly trafficked bridges, should be considered at an early stage to avoid the risk of additional collisions [18, 2, 17]. It is also necessary to prevent species that attract insects and hence indirectly bats from being planted at roadsides. For example, the use of certain conifers is preferable to nectar plants. [13]. Some authors recommend [25, 9] leaving a strip approximately 10m wide without woody vegetation on either side of the road. Impact reduction methods Mitigating the destruction of roosts The destruction of roosts is an extreme situation, which is to be avoided as far as absolutely possible. It should be carried out in the periods when the bats are the least vulnerable (i.e. outside birthing periods and hibernation). It is therefore generally recommended for this to be done in autumn, after the young have dispersed and individuals have not yet started to hibernate.

10 Sétra Information notes Economics Environment Design Serie n Localisation technique Ultrasound detector Automatic systems Radiotracking Chemical fluorescent capsules Light amplifier Infrared camera Thermal camera General principle Objectives Advantages Disadvantages The device makes the ultrasounds emitted by bats audible to humans Coupling of a presence detector (ultrasonic or infrared) with a recording system (video camera, still camera or audio recorder) Micro-transmitters are fitted to the backs of bats and their locations are determined by following their route Luminous capsule fitted to the bat s back Equipment that makes it easier to see bats in the dark Filming in complete darkness by lighting bats without disturbing them Recording the temperature difference between the animal and its environment - Ascertaining the presence of bats - Identifying species - Quantifying the bats and identifying their activities (foraging, movement) - Identifying zones or periods (times and seasons) when bat activity is high - Assessing the level of bat activity - Finding roosts - Discovering the movements made by individual bats between their roosts and their foraging areas - Ascertaining the extent of living areas - Detailed analysis of sensitive sites - Monitoring movement in flight - Observing behaviour in flight (flyway, crossing the road), counting individuals - Observing bats in their roosts - Filming bats - Filming bats - No individuals are captured, - Relatively easy to implement - Operates independently for a relatively long time - Provides a great wealth of data - Very useful for studying behaviour - Observations do not disturb the bats - Useful for roost exit counts - Observations do not disturb the bats - Observations do not disturb the bats - Species with weak sonar or that fly very high are underrepresented. - The direction bats are moving is not determined - Lengthy process of identifying species on a computer - Subject to vandalism - Makes great demands on human and material resources - Highly invasive, traumatic for the animals - Considerable amount of time required for data analysis - Difficult to obtain representative results - Operates for only a brief period - $Facilité de repérage limitée - Relatively expensive - Very energy consuming - Expensive to purchase - Expensive to purchase Table 2:Summary of location techniques for bat foraging areas and flyways Source: [1] Localisation technique Ringing Transponders General principle Objectives Advantages Disadvantages Placing a ring on the bat s forearm Monitoring overall displacement of individuals by comparing the location of marking (capture) and re-capture Microchips implanted under the skin which make it possible to identify an animal with a receiver ($capture marking re-capture device) - Assessing distances covered - Identifying an animal - Highly durable marking - Useful for evaluating migrations and the different roosts used by an individual in the course of its life - Long-term monitoring - The bats only need to be handled once - Often badly carried out, highly regulated nowadays Table 2a: Additional techniques for studying bats Source: [1]

11 Sétra Information notes Economics Environment Design Serie n A roost can only be destroyed with a permit. This is difficult to obtain, and requires extremely strong justifications (exemption from the prohibition of destroying the habitat of a protected species after a decision on the part of the CNPN 1, art. L411-1 and 2 of the French Environment Code). It is preferable to make sure the known or potential roost is unoccupied by bats immediately before any action is taken on the structure. The presence of a bat expert is also indispensable when known or potential roosts are destroyed in order to take any emergency measures that are necessary to save the animals [6, 18, 12]. If bats are found, exclusion procedures should be put in place, either by preventing them from returning to the roost or by disturbing them so they leave of their own volition [6, 18, 17, 22, 26, 27]. In forests, it is recommended to cut the trees down and leave them on the ground for two days while the bats leave the roost. Moving the trees in which the bats roost may also be considered [12, 13, 18]. Reducing disturbance During works In order to avoid disturbance to bat movements, night-time works in the vicinity of flyways and roosts should be avoided, at least during the periods when bats are the most sensitive (especially the birthing period) [12, 13, 18]. If nighttime works are inevitable, it is advisable to install very localized lighting in the worksite zone, avoiding surrounding areas in order to reduce the barrier effect [12]. The temporary installation of noise barriers and/or light screens may also be considered. Temporary works infrastructure (stockpile areas, roads for construction traffic) should also be constructed at a distance from roosts. After the road has been opened The construction of a road can also make it easier for the general public to reach some roosts. The number of visits can be limited by installing warning signs [3] or by protecting the site by installing railings to prevent access [13]. In the latter case, care must be taken not to alter the physical conditions that are indispensable for the bats to remain (temperature and humidity) [28]. The closure of the site can nevertheless encourage some visitors to enter it and damage the protection equipment. To prevent access to the site it is sometimes better not to prohibit access to the site but to make it difficult by installing a series of obstacles such as ditches, low walls and waterholes. Making road crossing points safe The experts are unanimously agreed about the need to connect safe crossing points with the surrounding habitats. To achieve this, there are a large number of proposals involving the installation of linear structures or fences that bats instinctively follow to the crossing point. Hedges and double hedges Installing hedges along the road can also guide bats to safe crossing points. These hedges may be either single or double. In the case of double hedges, [17], the first hedge should be broken in order to guide bats into the space between the two hedges and the second hedge should be continuous, acting as a barrier, dissuading bats from crossing the road. These hedges may be quite long. When a new road cuts across a linear structure which bats follow, it is also possible to modify the initial design of the plant corridor and guide the bats to a new safe crossing point (a bridge, footbridge or tunnel [12]. Figure 3: joining habitats using double hedges - Source: [1] 1 CNPN: Conseil National de Protection de la Nature

12 Sétra Information notes Economics Environment Design Serie n In this case, the advice is to retain the length of hedge for as long as possible in order to limit the abandonment of the flyway. Furthermore, the detour should not exceed 50m. This can be a highly effective measure, but some species appear not to change their habits and still cross the road at the same point. The time that is required for hedges to grow also reduces the effectiveness of the measure. Temporary netting or fencing can therefore be installed to avoid gaps [6, 13, 8]. Figure 4: leading bats to a safe crossing point Source: [1]] Wire netting, fences and walls A 2 metre high wire netting fence or a mound of earth at the sides of the road in order to guide bats towards a crossing may also be sufficient to make the zone safe [13]. However, this type of measure does not seem suitable for horseshoe bats that generally continue to fly across the road at low level. In forests, another possibility is to build a wall or a fence at the points where the maximum activity has been recorded (see drawing opposite) [12]. In France, it is nevertheless necessary not to lose sight of aesthetic and road safety issues. Roadside features (walls, poles, vegetation, etc.) must be positioned in such a way as to ensure they do not endanger road safety by providing new obstacles for road users. The regulations concerning distances and or safety barriers must be complied with [32]. Light barriers The use of lighting as a barrier or to increase the height at which bats fly is also occasionally recommended [21]. The lights are frequently vandalized and require maintenance (the area must be mowed so they are not covered by vegetation) and consume energy. The use of lighting is occasional and it has not always been shown to be effective. Figure 5: guiding bats towards a safe crossing Source: [1] This type of measure is recommended at road crossing points that are used by bats, in particular when the bats flyway lies between two lines of trees whose tops join forming a kind of green tunnel. According to the experts, this type of facility is only effective for certain species. Figure 6: bat scarers Source: [1] In Wales, 1 metre high lighting bollards have been installed at 10 metre intervals on either side of a road. The first observations show that scarers of this type are effective for horseshoe bats even if some individuals still cross the road in the lit section [21, 2, 13].

13 Sétra Information notes Economics Environment Design Serie n Hop-overs These are created by means of tall trees or wire netting (6 metres) with dense low vegetation to encourage bats to fly higher [12, 21]. In the case of a 2x2 lane dual carriageway, the literature recommends planting a tree (which does not attract insects) in the central reservation to ensure the bats continue to fly high. To prevent bats from crossing to the side of the hopover it is recommended to install wire netting along the road. It should be noted that in France, it is nevertheless necessary not to lose sight of aesthetic and road safety issues. Roadside features (walls, poles, vegetation, etc.) must be positioned in such a way as to ensure they do not endanger road safety by providing new obstacles for road users. The regulations concerning minimum distances and or safety barriers must be complied with [32]. Figure 7: encouraging bats to fly high Source: [1] More specific types of crossing can also be envisaged in order to guide bats across the road above vehicle level. When designing the southern bypass of the French city of Bourges, Arthur and Lemaire created a crossing structure (see diagram opposite) to guide bats and raise their height of flight. This system should avoid collisions and re-establish bat movements. Figure 8: guiding bats and increasing their height of flight: [30] The design of overpasses Overpasses, which were originally designed to enable wild animals, pedestrians, farm machinery and service vehicles to cross roads, overpasses are frequently used by bats when they do not appear to be too open and when they are connected to landscape structures. In order to encourage the use of such overpasses it is possible to consider additional measures [2, 21, 12, 9]. For example, it is beneficial to design wider structures than the traffic on its own would require in order to be able to plant a hedge of shrubs along the entire length of one side. A wooden fence or an opaque windbreak may be sufficient for some species (pipistrelle and lesser mouse-eared bats). The recommended height for the fence or the hedge is between 1.5m and 3-4m depending on the species. Figure 9: overpass design features that encourage use by bats Source: [1]

14 Sétra Information notes Economics Environment Design Serie n Underpasses Whether intended for wildlife or for a watercourse, it is useful to plant a funnelshaped line of vegetation at the side and the top of the tunnel entrance in order to encourage use by bats. Wire netting or a screen in front of the road can also lead bats to use the tunnel or fly above the traffic. Bats can also be encouraged to pass through an underpass by gradually reducing the height of the vegetation in the approach to the entrance. As bats generally fly at leaf height they will tend to lower their height of flight and pass through the underpass. Figure 10: planting of the underpass entrance to encourage bats to fly through the structure Source: [1] In addition, lighting should not be installed in underpasses intended for wildlife to avoid discouraging bats and leading them to use a more dangerous flyway. The passage of a watercourse through the underpass provides a very great incentive for bats. Although all species use underpasses, occasionally even very narrow ones, some authors have determined the minimum advisable dimensions of an underpass in order to encourage its use by the greatest number of species and individuals [18, 12, 2, 13]. In general, the recommendations of the experts all agree on one principle: the wider the passage the more it will be used by bats. A height of as much as 4.5m and a width of 4-6m has been advised in order to ensure that all species are able to use the underpass. The minimum size for a culvert is 1.5m, and the experts consider 3m is the optimum. When underpasses exceed 10m in length, it is recommended to double the diameter every 10m (comm. pers. Laurent Arthur, MHN Bourges). Insubstantial overpass structures Easily dismountable structures, often consisting of wires or wire netting stretched horizontally between two masts on either side of the road, have been trialled abroad. They may be installed either temporarily, in order to appraise the suitability of a location before installing more substantial structures, or as a permanent mitigation measure. This is a recent type of structure and its effectiveness is not yet proven, but it seems to have had some success already [2]. Figure 11: insubstantial overpass structures - Source: Billington [2], Sirhowy Enterprise [2] In France, such roadside features must be positioned so as to ensure they do not endanger road safety by providing new obstacles for road users. [32].

15 Sétra Information notes Economics Environment Design Serie n Perches for horseshoe bats According to some experts, planting groups of trees on roadside embankments may create areas where horseshoe bats wait until the traffic becomes lighter before crossing [17, 14]. Reducing collisions By optimizing the longitudinal profile As roads built on embankments are more dangerous, longitudinal profiles should be optimized in areas where bats are at risk. A road in a cutting thus provides a safer crossing point for bats (comm. pers. CPEPESC Lorraine, 2008). By not lighting roadsides In order not to attract insects and therefore bats, a few precautions should be taken with regard to road lighting: diffuse lighting should be avoided, lamps with a focused beam are to be preferred; lighting should be directed downwards and not shine on the surrounding vegetation [12]; sodium lamps, which are less attractive, should be used instead of mercury vapour lamps, and placed at the greatest possible height (6-8 m) and at some distance from the carriageway [17, 25]. By limiting access to vehicles Under normal traffic conditions, lethal collisions can occur even at low speeds so speed reduction would not seem to be a valid solution [12]. Nevertheless, installing speed reduction measures such as an interchange or a roundabout appears to be more effective [7, 18]. In France, the design of such measures should also take account of associated traffic management issues, the purpose of the road and road safety.

16 Sétra Information notes Economics Environment Design Serie n Auditory and magnetic scarers: proscribed measures The first tests of auditory scarers that used bat-warning cries seem inconclusive. Distressed bats appear to attract the curiosity of other bats, of all species. When positioned in a dangerous area such as the mast of a wind turbine or at the side of a road they seem to act as traps and have the opposite effect from what is intended. Impact compensation measures Alternative roosts We lack precise knowledge about the factors that determine whether bats accept or reject a roost. It is therefore very difficult to replace a roost that has been destroyed by an artificial one. They should in all cases be positioned where they do not place the bats in danger (avoid sites near a road) and match the needs of the species that is present in order to replace the original functions of the roosts that have been destroyed (hibernation, summer occupation, etc.). By replacing tree roosts [18, 12, 13] (comm. pers. CPEPESC Lorraine, 2008) The use of "bat boxes" is one possibility while a permanent alternative roost is under construction. It is best to improve their effectiveness by installing them two years before the start of the works. However, they are too frequently perceived as a miracle measure and some experts prefer bat boxes to be used only for prevention or study purposes. In addition their use may introduce constraints due to the need for maintenance and monitoring and their limited life span. Horseshoe bats do not use bat boxes (long-winged bats neither), or alternative roosts. In bridges [12, 3] Some bat species can easily form colonies in bridges, so modifying bridges to receive bats is straightforward and effective. Several possible measures are possible: fitting bridges with cornices with a space of 20 mm ± 5 mm between them; leaving spaces between the bridge and its supporting pillars; using expansion joints; creating hollow spaces under bridges. Figure 12: making the box girders of large structures accessible from the outside through formwork holes, inspection holes, etc. Source: [30] In buildings near the construction site [2, 12, 13] Modifying or making new openings in the roofs and attics of suitable buildings (churches). It is important to ensure that access to these sites is unlit. Alternative habitats To compensate for the loss of foraging areas, it is generally recommended to purchase and manage areas near those that have been destroyed. The main aim is to create habitats whose structure is favourable to flight and echolocation, to increase the variety and quantity of insects (forests, banks and ecotones), and increase the number of corridors in order to increase the areas, which bats can explore for food. In the context of these modifications, and in order to increase the abundance of associated insects, it is recommended to plant local non-resinous species preferentially. In addition, grassland should be mowed late in the season and the use of crop protection products reduced. When implementing these measures it is important to take account of the accessibility of the zone for bats, and in particular ensure that their flyways provide access to them.

17 Sétra Information notes Economics Environment Design Serie n Type of measure Removal or avoidance measures Measure Maintaining landscape structures Limiting the attractiveness of roadside vegetation The measures in more detail Examples (more details are given in the text) Marking structures that are essential for bats with flags, fences or tags, etc. Monitoring works No attractive plant species at roadsides Impact mitigation measures Compensation measures Mitigating the destruction of roosts Reducing disturbance Making crossing points safe Reducing collisions Alternative roosts Alternative habitats Action should be taken in the least sensitive periods Make sure the known or potential roost is unoccupied by bats just before any action. If bats are found exclusion measures should be put in place etc. Nighttime working should be avoided, temporary sites should not be located near roosts, etc. Limit the number of visits, avoid altering the physical conditions of roosts, etc. Hedges and double hedges Wire netting, fences and walls Light barriers Hop-overs The design of overpasses Underpasses Insubstantial overpass structures Perches for horseshoe bats By optimizing the longitudinal profile By not lighting roadsides By limiting vehicle speeds By replacing tree roosts In bridges In buildings near the construction site By purchasing and managing areas near those that have been destroyed Table 3: Summary of the measures proposed in the literature that are intended to protect bats from the impacts of land transport infrastructure Source: [1] 4. Current and future knowledge Overall summary The impacts of facilities on bats are a relatively large topic. Interest has nevertheless focused in recent years on the impacts of wind farms. However, gaps remain in our knowledge with regard to the impact of transport infrastructures on bats. This is probably due to the difficulty of studying this group of animals, which, in addition to being nocturnal, move, like birds, in three dimensions and whose different species exhibit considerable differences in behaviour. Our analysis of some sixty national and international bibliographical references [1], many of which related to roads, has shown that transport infrastructure is responsible for the death of a large number of bats and that the impacts are mainly due to two factors: mortality as a result of collisions; environmental threats due to the destruction of flyways and foraging areas.

18 Sétra Information notes Economics Environment Design Serie n As these factors have now been fairly clearly identified, they already frequently provide the basis for analyses that are conducted in the framework of environmental studies. Although our current knowledge is incomplete, it generally seems able to identify the impacts of a project even if it contains some recurrent gaps (impacts in forests, impacts on certain species horseshoe bats, etc.). At the same time, because of our increasing knowledge about species, and also probably as a result of changes in the regulations, more and more measures are being implemented to take account of bats in transport infrastructure design. However, it is apparent that the proposals, which are often taken from the same publications, are frequently confined to measures that have either never been implemented or whose effectiveness has never been evaluated. The situation in France The situation in France as described in the literature (general studies on bats, population monitoring, studies conducted in the framework of road, motorway and railway design projects, surveys required by the LOTI (Domestic Transport Policy Act) and interviews with bat experts (in particular MHN Bourges and CPEPESC), highlights how little experience we have on bats and transport infrastructure [1]. The information in the bibliography essentially relates to potential impacts and proposed measures. While monitoring is almost systematically recommended in impact documents, very little feedback is received. The increasing amount of attention given to this issue in transport infrastructure construction or modification projects should however fill some of the gaps in our current knowledge. Outlook The publication of this information note, which summarizes present-day knowledge, and the preparation of a technical guide on infrastructure and bats help further the goals of the bat restoration plan. However, it would be worthwhile to carry out a considerable amount of additional research, in particular on collisions and monitoring the effectiveness of crossings with a view to: understanding the behaviour of juveniles when crossing roads; identifying the real influence of speed and traffic density; evaluating the effectiveness of structures according to their size; evaluating the effectiveness of insubstantial overpass structures; taking account of forest bats; use and impacts of pavement runoff water treatment basins; identifying and investigating scarer systems.

19 Sétra Information notes Economics Environment Design Serie n Bibliographie [1] Sétra / Cete, Routes et chiroptères. Etat des connaissances. Rapport bibliographique. 67 p p de fiches bibliographiques annexes. [2] Highways Agency, Best practice in enhancement of highway design for bats. Revue de littérature. Halcrow Group Limited. 52 p. [3] Keeley B.W., Tuttle M.D, Bats in American bridges. Scientific article, Resource Publication No.4. 6 p. [4] ECOCONSEIL - CPEPESC Franche-Comté, Étude d incidence de la LGV Rhin-Rhône sur le site Natura 2000 "Mine d Ougney". Rapport final s inscrivant dans l APD du projet. 52 p. [5] Roué S.Y. - CPEPESC Franche-Comté (1999). Étude biologique sur la bande du projet routier Lure-Vesoul (RN19) - Les chiroptères et leurs gîtes. Rapport. 22 p. [6] National Road Authority, Guidelines for the treatment of bats during the construction of national road schemes. 13 p. [7] Capo G., Chaut J.-J. et Arthur L, Quatre ans d étude de mortalité des chiroptères sur deux kilomètres routiers proches d un site d hibernation. Article scientifique. Symbioses n 15. pp p. [8] Vaine A, Études et suivis des chiroptères du Gouffre de La Fage. Rapport de stage de BTSA GPN. 56 p. [9] Néri F., Chauve-souris et aménagement routier. Bulletin de liaison "KAWA SORIX" du Groupe chiroptères Midi-Pyrénées. 1 p. [10] Lemaire M. et Arthur L., Les chauves-souris et les routes. Actes des 3 èmes rencontres "Routes et Faune Sauvage". 460 p.. pp p. [11] Girons M.-C., Notes sur les mammifères de France. Les Pipistrelles et la circulation routière. Note Mammalia tome 45, n 1. pp p. [12] Limpens H.J.G.A., Tweesk P. et Veenbaas G., Bats and Road Construction - Brochure about bats and the ways in which practical mesures can be taken to observe the legal duty of care for bats in planning, constructing, reconstructing and managing roads. Technical handbook. 24 p. [13] Bickmore C. et Wyatt L., Review of work carried out on the trunk road network in Wales for bats. Bibliographic study. 65 p. [14] Bickmore C. et Wyatt, (Traduction Laurent Arthur)., Synthèse des travaux conduits pour les chauves-souris sur une route nationale au Pays de Galles (Country Council of Wales, juillet 2003). Scientific article. Symbiose, n 15. pp p. [15] Lesiński G., Bat road casualties and factors determining their number. Scientific article. Mammalia (2007). pp p. [16] CPEPESC Lorraine, Étude d incidences du projet de mise à 2x2 voies de la RN 59/159 entre Rémomeix et Frapelle (88) en rapport au site Natura 2000 FR "Gîtes à chiroptères autour de Saint Dié (88)". Rapport. 40 p. [17] Lemaire M. et Arthur L., Les chauves-souris, maîtresses de la nuit. Livre Ed. Delachaux et Niestlé (réed. 2005). 265 p. [18] Highway Agency, Nature conservation advice in relation to bats. Design manual for roads and bridges. Guide technique. 34 p. [19] Devos S., Raevel P., Govaere A., Vaillant J.C. et Devos R. - Greet Ingénierie / E.E.D. France, Nouvelles techniques d investigation par radar des peuplements de chiroptères. 5 p. [20] Arthur L., Lemaire M., Souchet C., Brazillier D., Duteil D., Anisensel F., Ponts et chauves-souris. Article du Bulletin de liaison n 24 "Ouvrages d art". 7 p - Sétra [21] National Road Authority, Best Practice Guidelines for the Conservation of Bats in the Planning of National Road Schemes. Technical handbook. 44 p. [22] Maugard J-P. - DDE Cher, Les chiroptères et les ouvrages d art dans le département du Cher. Rapport d étude. 31 p. [23] Arthur L. et Lemaire M., Résultats des premiers aménagements d ouvrages d art pour les chiroptères dans le département du Cher. Acte du colloque "Gestion et protection des chauves-souris : de la connaissance aux aménagements". 4 p.

20 Sétra Information notes Economics Environment Design Serie n [24] Bat Conservation Trust, Bat Surveys Good Practice Guidelines. Technical handbook. 83 p. [25] ECOLOR, Conservatoire du patrimoine naturel de Champagne Ardenne, Document d incidences Natura 2000 "Fort de la Bonnelle". Rapport 22 p. [26] Pénicaud P., Les chauves-souris et les arbres : connaissance et protection. Plaquette d information MATE. 2 p. [27] Magnin B., Sauvetage de la colonie de Grands Murins du pont de Corbières. Acte du colloque gestion et protection des chauves-souris : de la connaissance aux aménagements. 4 p. [28] Harouet M. et Monfort D., La protection des chauves-souris. Bulletin de la société des sciences naturelles de l Ouest de la France - n 3 - Tome p. [29] Kiefer A., Merz H., Rackow W., Roer H. et Schlegel D. (1995). Bats as traffic casualties in Germany. Article scientifique. Myotis n 32-33, pp [30] Sétra-Medd, Aménagements et mesures pour la petite faune, Guide technique. 264 p. [31] Néomys, Projet d aménagement de la RN 66 dans la vallée de la Moselle entre Ferdrupt et Fresse-sur-Moselle (88). Dossier d évaluation des incidences au titre de l Article L414-4 du Code de l Environnement (Chap. IV, Section 1) - Complément à l étude d impacts - Expertise chiroptérologique. Rapport. 20 p. [32] Sétra, Traitement des obstacles latéraux sur les routes principales hors agglomération. Guide technique. 131p. [33] EUROBATS, Mise en œuvre de l accord relatif à la conservation des chauves-souris en Europe. Rapport national de la France. Regulations and action plan Order of 23 April 2007 setting out the list of mammals that are protected in all parts of France and the terms of their protection (Journal Officiel de la République Française of 10/05/2007). Bonn Convention of 23 June 1979 on the Conservation of Migratory Species of Wild Animals (Journal Officiel de la République Française of 30/10/1990). Bern Convention of 19 September 1979 on the Conservation of European Wildlife and Natural Habitats (Journal Officiel de la République Française of 28/08/1990 and 20/08/1996). European Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and flora (Habitats and Species Directive) (Journal Officiel de la République Française of 22/07/1992). Bat restoration plan for metropolitan France. September 2007 SFEPM Ministère de l Ecologie, de l Energie, du Développement Durable et de l Aménagement du Territoire. To find out more A more complete bibliography is available in the report, which provided the basis for this Information Note [1] (

21 Sétra Information notes Economics Environment Design Serie n Appendix Family Species Status Horseshoe bats Greater horseshoe bat [Rhinolophus ferrumequinum] NP, HSD+IV, BernII, BonnII France counts four members of this family Lesser horseshoe bat [Rhinolophus hipposideros] NP, HSD+IV, BernII, BonnII whose members are recognized by the horseshoe-shaped protuberances on their noses Mediterranean horseshoe bat [Rhinolophus euryale] NP, HSD+IV, BernII, BonnII from which ultrasounds are emitted. Méhely s horseshoe bat [Rhinolophus mehelyi] NP, HSD+IV, BernII, BonnII Vesper bats This is the largest family of bats in France, with a total of 28 species. Their distinctive feature is their tragus (a projection inside the auricle) but their morphology varies considerably from one species to another. The species are in fact often identified on the basis of the length of their forearm and the shape of their ears. Long-winged bats There is only one species of this family in France, which is characterized by its short snout and arched forehead. Free-tailed bats These are distinguished by the fact that their tail is considerably longer than the posterior part of their wing. Only one species is found in France, the European free-tailed bat. Barbastelle [Barbastella barbastellus] Daubenton s bat [Myotis daubentonii] Long-fingered bat [Myotis capaccini] Pond bat [Myotis dasycneme] Whiskered bat [Myotis mystacinus] Brandt s bat [Myotis brandtii] Alcathoe bat [Myotis alcathoe] Bechstein s bat [Myotis bechsteinii] Natterer s bat [Myotis nattereri] Long-eared myotis [Myotis escalerai] Geoffroy s bat [Myotis emarginatus] Greater mouse-eared bat [Myotis myotis] Lesser mouse-eared bat [Myotis blythii] Maghrebian bat [Myotis punicus] Common noctule bat [Nyctalus noctula] Greater noctule bat[nyctalus lasiopterus] Leisler s bat [Nyctalus leisleri] Northern serotine bat [Eptesicus nilssonii] Serotine bat [Eptesicus serotinus] Parti-coloured bat [Vespertilio murinus] Kuhl s pipistrelle [Pipistrellus kuhlii] Nathusius s pipistrelle [Pipistrellus nathusii] Common pipistrelle [Pipistrellus pipistrellus] Soprano pipistrelle [Pipistrellus pygmaeus] Brown long-eared bat [Plecotus auritus] Grey long-eared bat [Plecotus austriacus] Alpine long-eared bat [Plecotus macrobullaris] Savi s pipistrelle [Hypsugo savii] Common bent-wing bat [Miniopterus schreibersii] European free-tailed bat [Tadarida teniotis] The 34 species of bat and their protection status NP, HSD+IV, BernII, BonnII NP, DHIV, BernII, BonnII NP, HSD+IV, BernII, BonnII NP, HSD+IV, BernII, BonnII NP, HSD V, BernII NP, HSD+IV, BernII, BonnII Species newly discovered in France (2009) NP, HSD+IV, BernII, BonnII NP, HSD+IV, BernII, BonnII NP, HSD+IV, BernII, BonnII NP, HSD V NP, HSD V, BernIII, BonnII NP, HSD V NP, HSD V NP, HSD+IV, BernII, BonnII NP, DHIV, BernII, BonnII Status: NP (Nationally protected), HSD+IV (EEC Habitats and Species Directive - Appendix IV), BernII (Bern Convention - Appendix II), BonnII (Bonn Convention - Appendix II)

22 Authors François NOWICKI CETE de l'est téléphone : 33 (0) télécopie : 33 (0) mél : francois.nowicki@developpement-durable.gouv.fr Liza DADU CETE de l'est téléphone : 33 (0) télécopie : 33 (0) Jean CARSIGNOL CETE de l'est téléphone : 33 (0) télécopie : 33 (0) mél : jean.carsignol@developpement-durable.gouv.fr Jean-François BRETAUD CETE Normandie-Centre téléphone : 33 (0) télécopie : 33 (0) mél : jean-francois.bretaud@developpement-durable.gouv.fr Sabine BIELSA Sétra téléphone : 33 (0) télécopie : 33 (0) mél : sabine.bielsa@developpement-durable.gouv.fr Document validé par le Muséum d'histoire Naturelle de Bourges (Laurent ARTHUR) Technical information Sabine BIELSA Sétra téléphone : 33 (0) télécopie : 33 (0) mél : sabine.bielsa@developpement-durable.gouv.fr Warning The series of the Setra Information Notes is meant to supply a rapid information. The counterpart to this swiftness is a risk of error and, or, a lack of exhaustiveness. This document cannot involve the liability of its author nor that of the Service. The companies, the names of which appear in this serie, are mentioned as examples of applications that are deemed as necessary to a good understanding of the text and a good implementation in practice. Sétra belongs to the scientific and technical network of the French Public Works Ministry. Service d'études sur les transports, les routes et leurs aménagements 46, avenue Aristide Briand BP Bagneux Cedex France téléphone : 33 (0) télécopie : 33 (0) This document is available on the Sétra's website: Internet : Intranet (Réseau ministère) : Sétra authorization is required even for partial reproduction of this document. Référence : 1120w ISSN : The Sétra belongs to the scientific and technical network of the French Public Work Ministry (RST) Le Sétra appartient au Réseau Scientifique et Technique du MEDDTL