Wildlife Considerations on Toll Roads in France

John Kinar, Wisconsin DOT
(608) 266-1202 and Alex Levy, FHWA, (404) 562-3920.

Deck of New "Green Bridge" in France

Requirements

Environmental impact studies are an integral part of the technical and financial analysis for transportation projects in France. Here, they are evaluated at each stage of project development, and must address both habitat impacts and demonstrate a commitment to wildlife preservation. As in Germany, the first imperative is avoidance. When sensitive areas cannot be avoided by a transportation project, mitigation is required.

Observations

Our field time focused on motorways in the Loire River Valley south of Paris. Located in one of the nation's largest agricultural regions and famous for its palatial chateaus, we toured two routes: one actively used major north-south thoroughfare, and a newer route still under construction, but nearing completion with newer materials. Both routes are toll highways built and maintained by Cofiroute, a private company, under a long-term construction and operations contract with the French government. Even as a private entity, Cofiroute must comply with regulations requiring attention to wildlife habitat and connectivity issues.

The group observed a number of mitigation features for amphibians, including concrete trenches, fenced barriers, and substitute habitat ponds. Mitigation features for deer and other mammals included green bridges, underpasses, and extensive right-of-way fencing. Larger animals typically found near the highway include deer, fox, and wild boar.

Fencing for deer was typically 2.8 meters high while for boar it was 1.2 meters. Graduated mesh was placed at the bottom of some fences to a height of about one meter to keep smaller animals off the highway. Fencing is also typically buried to a depth of about 40 cm to prevent access to the motorways by burrowing animals.

In France, wildlife connectivity features are typically considered only as part of new construction projects. The French indicated that constructing green bridges over active thoroughfares was cost prohibitive. That said, it is estimated that there are as many as 250 crossings system wide.

Fencing for Wildlife Exclusion in France

Findings

Throughout France there are about 20,000 collisions per year with large animals. Most occur at dusk and dawn and are generally attributed to the rapid growth in the size of the deer herd, the speed of the motorist, and inattentive driving.

A critical consideration for animal crossings is the impact of land management activities by private property owners adjacent to the crossing. High fences installed by landowners or modifications in land use could easily impede the movement of animals in the very location of a crossing, greatly reducing its effectiveness. To address this concern the French recommended that about two hectares of land on either side of a crossing be controlled by agreement, easement, or direct purchase to help assure continued connectivity.

Another critical element of an animal crossing project is monitoring its use following construction. Current protocol in France calls for monitoring crossing use the first year, with follow-up monitoring the third and fifth years. We were told that the use of sand beds as a monitoring tool requires at least twice weekly visits and may occur over a period of several years. Some crossings are less used than others. Possible causes being investigated include noise, lighting, crossing size, and openness.

We were informed that even when construction funds are available to build animal crossings and related features, adequate maintenance funds may be unavailable and long-term maintenance may suffer. As one individual stated, " . . . our mentality is not on maintenance". This is a critical shortcoming that must be addressed to assure the long-term success of these projects.

Green bridge under constructon on new toll facility in France.

The French design of green bridges that we observed, favored an hourglass shape with a 12-meter width at the center of the structure. While the French cited early Swiss research as the basis for these structures, this contrasted with the more recent results from the Swiss Ornithological Institute research that recommends an optimum structure width of 50 meters. Furthermore, the Swiss also demonstrated that the cost of engineering and constructing an hourglass shape was equal to that of a similarly dimensioned rectangular structure, with the funneling effect provided by planted vegetation.

While our hosts acknowledged that the larger size would provide for greater transparency and connectivity, they nonetheless felt that 12-meters was sufficient to get occasional usage. They acknowledged that their intent was not so much to facilitate habitat connectivity, but was driven by hunting interests to provide enough connectivity to maintain genetic diversity in game populations.

Our French hosts were very gracious, informative, and shared their insights freely. With little introduction, they escorted us directly to the field and through a grid locked Parisian freeway system that seems all too familiar. We truly appreciated the time they spent preparing for our visit and serving as our guides while we were there.