PDDG Chapter 14 - Wildlife Accommodation

Chapter 14 of the MassDOT Project Development and Design Guide

14.1 Introduction

According to an FHWA study, vehicle collisions kill 1-2 million large animals every year in the US, and cause 200 human fatalities and over 26,000 injuries, at a cost to Americans of more than $8 billion annually. In Massachusetts, State Farm Insurance claim data indicates that 1 out of 109 claims are likely generated by colliding with a deer or other large animal. Wildlife crossing structures with associated elements such as fencing, have been shown to reduce motorist collisions involving wildlife by up to 97%, reducing the monetary and the societal costs of those crashes, including lost lives, injuries, and property damage.

In addition to wildlife/vehicle collisions (WVC) which cause mortality and injury to animals and humans alike, roadways also have a variety of other impacts on wildlife populations, habitat, and ecological functions. All of these impacts can be reduced through appropriate design considerations. This chapter summarizes the documented effects that roads have on wildlife and their habitats, describes measures to incorporate along new and existing roadways to minimize these effects, and provides a high-level summary of wildlife crossing structure guidelines. A great deal of information is available on WVCs, as well as the effects of roads on wildlife, and some practical solutions to successfully mitigate both have been identified. In most cases, to be successful, these wildlife accommodations must be designed and implemented to address the specific habitats, topography, and species that are present where the roadway in question is located.

Most roads and other forms of linear transportation infrastructure were originally designed to transport vehicles, with little understanding about or consideration for the diverse terrestrial and aquatic landscapes they transect. Since the 1990s, studies have begun to focus on the relevance of the road in a landscape context and its effects on that landscape. The science of road ecology, broadly defined as the study of “the interaction of organisms and their environment linked to roads and vehicles” (Forman et al. 2003) was born and continues to evolve today. Understanding road ecology requires participation and input from biologists, hydrologists, transportation planners, and engineers. In a landscape context, roadway networks connect human communities but often separate natural habitat components as they cross mountains, valleys, streams, forests, and farmland. Rainfall infiltration and drainage patterns may be altered when they encounter a roadway, and runoff from roads may cause reduced water quality in receiving waters. Habitats near roads may change through vegetation management and the introduction of non-native species along a linear right-of-way (ROW). Microhabitats adjacent to roads are often vastly different from nearby macrohabitats in terms of temperature, vegetation structure and composition, and substrates.

Road ecology also provides tools and insight for addressing WVCs, which, in addition to impacting wildlife, create a substantial public safety issue as described in the introduction above. For example, in northern New England, one in every 75 motor vehicle collisions with moose (Alces alces) results in a human fatality, as does one in every 2,500 collisions with white tailed deer (Odocoileus virginianus). Collisions with large mammals, such as deer, moose, and black bear (Ursus americanus) also result in high annual property damage costs. MassDOT recognizes the importance of implementing wildlife accommodations to reduce impacts to wildlife and improve habitat connectivity. However, the emphasis on public safety is paramount and cannot be overstated. As a transportation agency, MassDOT first and foremost functions to provide safe and efficient transportation infrastructure for motorists, bicyclists, and pedestrians. Designers can use concepts from road ecology to help identify effective measures to reduce the rate of WVCs and their associated costs. It is also important to note that wildlife accommodations that reduce WVC-associated costs thereby offset costs of including these features into a highway project. A study published in 2022 by Washington State University examined the cost/benefits of wildlife crossing structures in Washington State and determined each crossing structure saved an estimated $235,000 to $443,000 annually, due to reduced costs of property damage, injury, and death. The research suggests that the cost of building these wildlife crossings will be outweighed by the structure’s benefits over time. A similar 2023 study in Utah projected a $15 million cost savings over the life of a wildlife overpass, more than double the cost of its construction.

When designing and prioritizing roadway wildlife accommodations, it is important to consider the needs of rare versus common wildlife species in addition to human safety. Studies have shown that mortality from vehicles is a threat to wildlife populations when population numbers are already low or when critical habitats occur near roadways. The survival of rare species who depend on habitats transected by roadways may depend on implementing effective accommodations. In Massachusetts, many state-listed reptiles and amphibians meet this definition, primarily because of a dependence on at least two distinct habitat types (i.e., uplands and wetlands) that are frequently separated by roads. For example, studies have shown that roads have substantial adverse effects on species, such as the State endangered Blanding’s turtle (Emydoidea blandingii), whose primary range is densely populated northeastern Massachusetts. Female Blanding’s turtles may travel up to a mile in search of a suitable nest site and are likely to cross at least one road to do so, exposing them to traffic mortality.

Designers should consider the following issues and use the decision tree in Figure 14‑1 when designing and prioritizing where to integrate wildlife accommodations into roadway projects.

Figure 14.1: Wildlife Accommodation Requirement Scenarios

Image description

Source: MassDOT, BioMap

14.2 Types of Effects

Vegetation management within the ROW adjacent to roadways creates habitat valuable to some forms of wildlife, and some structures to facilitate wildlife movement are already in place where wildlife can pass under roadways by using existing bridge and culvert structures. However, roadway impacts on wildlife are generally negative. Studies have shown that some species avoid roadways and adjacent areas because of increased noise, pollution, visual disturbance, and predators using roadways as corridors. Traffic speed and density also contribute to wildlife avoidance and barrier effects. Other types of effects are less obvious but are also detrimental to wildlife, including habitat loss, habitat fragmentation, altered habitat quality, population fragmentation, and disruption of processes that maintain regional populations. The following sections briefly describe the effects roadways can have on wildlife.

Vehicle-Caused Mortality

WVCs are a worldwide phenomenon that injure or kill millions of animals annually. Wildlife mortality from vehicles affects all types of species, from hoofed species (such as deer and moose) to winged species (such as songbirds and raptors) and smaller species (such as amphibians, reptiles, and invertebrates, including dragonflies and butterflies). Wildlife mortality from vehicles is more likely to affect species with large home ranges and those that must migrate to different habitats to complete their life cycle. Animals with large home ranges are likely to encounter roads in multiple locations as they travel across their habitat, especially in Massachusetts. With 900 people per square mile, Massachusetts is the third most densely-populated state in the country (behind New Jersey and Rhode Island). Public and private roads are knitted across habitats from the Berkshires to the coastal plain and connect the 351 municipalities across the Commonwealth.

Some long-lived wildlife species with low reproductive rates, such as turtles, are particularly vulnerable to population declines due to the loss of adults to road mortality. Also, populations with few individuals are more affected because of the relative importance each individual plays in maintaining a healthy population. Temporal and seasonal variations are also evident. More white-tailed deer are struck by cars at dawn and dusk than any other time of day, and moose collisions are most likely to occur in the spring and fall. Large amphibian migrations occur in early spring. Female turtles cross roadways to reach nesting areas in June.

The rate of WVC and wildlife mortality from vehicles is influenced by traffic volumes, traffic speed, roadway width, adjacent landscape, and wildlife behavior and physiology. To date, the literature presents conflicting information on traffic volumes, but most researchers agree that increasing traffic volumes pose greater threats to wildlife up to a certain critical point, at which wildlife avoid roads altogether. Research suggests that roads with less than 1,000 vehicles per day (vpd) may cause road avoidance in smaller species, but crossing movements will still occur frequently. Roads with greater than 10,000 vpd likely pose an impenetrable barrier to wildlife, deterring most wildlife from crossing and killing many that do attempt to cross.

Research indicates that some wildlife is affected more by traffic speed than volume. For example, one study concluded that rabbits and songbirds experienced higher mortality rates at speeds greater than 40 miles per hour (mph). In Pennsylvania, deer-vehicle collisions decreased when the speed limit was reduced. The surrounding context and roadway design features also influence mortality. For example, deer vehicle collisions in Pennsylvania were lower when there was a higher number of residences and buildings near roads, when there was a greater distance to wooded areas, and when the minimum sight distance was increased.

Habitat Loss

Habitat is lost when an area previously providing food, cover, shelter, or breeding habitat is developed, including roadway footprints. As with road mortality, different species have different responses to habitat loss. Species that are long lived with low reproductive rates, large home ranges, and low densities (such as many large carnivores), may suffer greater negative impacts associated with habitat loss.

Habitat Fragmentation

Fragmentation is defined as the division of large and continuous tracts of habitat into smaller patches. Habitat fragmentation results from all types of habitat conversion, including for agriculture, urbanization, transportation, or other ROW modifications. In general, fragmentation of habitat is viewed as detrimental when considering the original native, climax species composition and abundance, natural history, and relative ecological stability of unmanaged plant and animal populations. Habitat fragmentation has a variety of associated effects, which are described below.

Reduction in Patch Size

Fragmentation of large areas of forest, grassland, or wetland habitat is likely to reduce the number of species occupying those habitat patches. In part, this is because smaller patches cannot support enough individuals to maintain viable populations for all species likely to be found in large patches. In addition, there are many area-sensitive bird species that simply avoid smaller areas of otherwise suitable habitat.

Edge Effects

In fragmented habitats, there is a proportional increase of habitat edge. Habitat edge is the transitional zone from one habitat community to another, such as the zone between pasture and forest. Habitat edge generally signifies habitat that is more susceptible to edge effects, such as predation and parasitism. The species richness of these areas is often higher than that of either bordering habitat because edges contain species from both habitats. However, species that are more successful near edges may negatively affect forest interior species and contribute to indirect effects of fragmentation.

Edge effects include a range of beneficial and detrimental ecological consequences that are associated with habitat diversity, the most common of which are increased predation and parasitism. Predation effects nearer the edge are most likely attributable to larger predators, such as crows (Corvus brachyrhynchos), blue jays (Cyanocitta cristata), raccoons (Procyon lotor), and snakes, that tend to use and follow forest edges. In addition, brown-headed cowbirds (Molothrus ater) are commonly found in edge habitats, particularly in agricultural areas, and are nest parasites of many songbirds, laying their eggs in other birds’ nests. Edges may also allow invasive plants species to colonize newly-disturbed areas adjacent to roadways, which decreases habitat quality. In addition, indirect effects of transportation improvements, such as altered microclimates near edges, may further decrease suitability for the original occupants of a forest, such as butterflies, damselflies, and other insects.

Barrier Effects

Many species require more than one habitat type to successfully carry out breeding, feeding, or other required functions. The barrier effect that infrastructure creates can physically or psychologically restricts movements or migration within a corridor that wildlife is either unwilling or unable to cross. . Connectivity to other patches, or habitat types, in the landscape may be reduced by roads, constituting a barrier effect.

Isolation of populations due to the barrier effect of roads may lead to reduced genetic diversity. Researchers in Germany found that a bank vole (Clethrionomys glareolus) population separated by a highway experienced significant genetic variation, but not within populations separated by a county road. Barriers may also lead to reduced ability for individuals, such as young of the year, to colonize new areas and can also cause difficulties for reproducing adults to locate one another.

The permeability of a road (i.e., the degree to which it presents a barrier to wildlife) is influenced by the adjacent roadside habitat and the availability of locations where wildlife can safely cross the roadway. For example, a roadway with a wide cleared roadside will be relatively more impermeable to a forest dwelling species than a road with suitable forested habitat adjacent to the road. However, the cleared roadside may benefit other species by providing a visibility zone to drivers and wildlife attempting to cross.

Barrier effects may also result in species being unable to complete a portion of their life cycle. For example, mole salamanders (Ambystomidae) spend most of their lives in forested uplands and wetlands, breeding only in seasonal pools known as vernal pools. If an impermeable road separates the two habitats, the ability to successfully reproduce and maintain a population may be reduced or eliminated.

Population Fragmentation

Smaller, isolated populations of plant and animal species are more susceptible to genetic deterioration because of inbreeding, depression, and genetic drift, possibly resulting in extinction.

Altered Habitat Quality

Most of the effects roads have on habitat quality are negative, as the presence and use of roads results in removal of vegetation; introduction of invasive plants; changes to water quality, run-off, and infiltration; introduction of a variety of pollutants; and introduction of disturbance due to noise and activity. For example, reduced habitat quality has been documented for birds adjacent to high-volume roads, primarily from noise associated with passing vehicles that may interfere with the ability of breeding males to successfully establish territories and attract females. However, other research found no difference in the number of breeding birds adjacent to highways from numbers at a greater distance, presumably because the roadside and median provided acceptable breeding habitat.

Not all habitat modifications are negative. Beneficial habitat adjacent to roads can be created for amphibians in roadside ditches, perching sites for raptors, and corridors for various wildlife. Roadside habitat increases in value when roadsides and medians are planted with native species and mowed less frequently. Designers must carefully balance the habitat benefits of unmowed roadsides with the safety effects of such conditions. Creating an attractive habitat along a roadside can also have negative consequences for wildlife. Amphibians may attempt to breed in roadside ditches or detention ponds, where conditions are not suitable for successful reproduction. Wildlife attracted to roadside habitats or roadside food sources (such as plantings or carrion of road-killed animals) may be subject to higher mortality.

In addition to terrestrial habitats, transportation infrastructure also affects aquatic ecosystems, due to increased water runoff and alteration of runoff patterns. Increased runoff may increase erosion, causing decreased water quality through sedimentation and higher pollutant loading. Highway runoff may also affect vegetation composition and aquatic species, especially in areas with heavy traffic. For example, salt laden runoff from roads and highways can facilitate the invasion of Phragmites into wetlands. Appropriate drainage system design can help mitigate these impacts.

14.3 Types of Wildlife of Accommodation

There are three primary approaches to reducing or mitigating the effects that roadways have on wildlife, which are influencing human behavior, influencing wildlife behavior, and changing roadway design. As discussed below, the first two approaches have limited utility. Designing roadways to minimize impacts—primarily through adding structures that that allow for wildlife to safely cross roads—and directing animals to these crossing yields the greatest benefits, and these design-based approaches are discussed in the next Section of this document.

Influence Human Behavior

Techniques to mitigate the impacts that roadways have on wildlife by influencing human behavior focus on reducing WVCs, and these approaches have been shown to have limited success. Mitigation techniques that attempt to lower WVCs by altering human behavior include:

• Signage
• Animal detection technology
• Public education and awareness
• Roadway lighting
• Reduced speed limits

Signage

Installing wildlife crossing signs where traditional wildlife pathways intersect highways can alert drivers to potential encounters with wildlife. Although the ability of these signs to reduce vehicle collisions with animals has not been proven, they may heighten driver awareness of wildlife mortality problems. Variability in signage increases the possibility of motorist observance. For example, Maine placed signs along roads during high deer and moose activity periods and found that collision frequency was lower than in areas where signs were left in place year-round. In addition to seasonal signage, some states in northern New England have instituted “fatality signs.” These signs are updated regularly to reflect the current number of motorist fatalities from moose and deer collisions.

Public Education and Awareness

Public education can include educational videos distributed at driver education classes and distributing maps at rest areas, visitor centers, welcome centers along major roadways, and local Registries of Motor Vehicles that detail types of common crashes, likely causes, and ways to avoid being in a wildlife-related crash.

Reduced Speed Limits

Maine evaluated data through 1998 for moose and deer crashes and found that most crashes occur on roads with speed limits of 50 to 55 mph, indicating that many crashes are caused by drivers whose decision distance is greater than the distance that can be seen under headlight illumination.

Influence Wildlife Behavior

Mitigation techniques that attempt to alter wildlife behavior include:

• Habitat alteration
• Hazing
• Whistles
• Mirrors and reflectors

Devices such as high frequency whistles attached to vehicles, increased highway lighting, reflectors (e.g., those manufactured by Swareflex®) placed along highway shoulders, and hazing have been tested to scare wildlife, particularly deer, away from oncoming traffic. However, results of studies on the effectiveness of these techniques indicate they are ineffective in reducing WVCs and are not discussed further in this chapter.

Habitat Alteration

To reduce wildlife/roadway conflicts, habitat alteration can be employed to repel wildlife from roadsides and medians and provide motorists with adequate visibility to avoid hitting wildlife that venture too close to the roadway. Alteration can consist of removing vegetation along roadways and/or planting vegetation adjacent to roadways that is undesirable to wildlife. Additionally, mowing regimes could potentially be designed to reduce foraging opportunities that may attract wildlife to the roadside. Roadsides and medians are usually mowed for safety reasons, as untrimmed vegetation reduces visibility adjacent to roads and potentially increases risks to wildlife, pedestrians, and bicyclists due to reduced sight distances.

Washington State, among others, employs a three-tiered approach to roadside vegetation management. There are three zones adjacent to a road, and vegetation is cut at different rates and to different heights. The purpose of this is to allocate maintenance resources effectively, but it is also useful for ecological management.

14.4 Reducing Wildlife/Roadway Conflicts Through Design

Research suggests that the following general approaches can effectively address wildlife/roadway conflicts. To the extent possible, MassDOT will consider adopting these actions as part of roadway project design and maintenance. Most of MassDOT’s roadway design opportunities will apply to repairing and improving existing roads, rather than new roads. Most of these actions can be readily added to roadway repair and upgrade projects.

• Conduct landscape-based analyses to identify important “connectivity zones” for wildlife and prioritize these areas for mitigation.
• Evaluate road-stream crossings for their barrier effects and prioritize structures for replacement (see Massachusetts Stream Crossings Handbook).
• Perforate road corridors frequently with wildlife and water crossings structures to reduce the road barrier effect and habitat fragmentation.
• Depress roads and/or use soil berms and vegetation to reduce traffic disturbance and noise effects on wildlife and adjacent residential areas.
• Collect and consolidate traffic, including trucks, and channel it onto primary roads to reduce both noise and barrier effects on lower-classification roadways.
• Consider design features and fencing to keep wildlife off high-volume roadways.

Design features that can reduce wildlife/roadway conflicts are described and illustrated below.

Wildlife Crossing Structures

Crossing structures can move wildlife either over or under a roadway, with the goal of maintaining natural population movements and reducing roadkill. Several factors, such as location, hydrology, light, openness ratio (cross sectional area of a culvert divided by its length), and cover are important in designing successful wildlife crossing structures. Overall, crossing structures should maintain landscape connectivity rather than redirect wildlife movements. Therefore, they should be placed in known wildlife migration/travel routes.

Determining species distribution and corridors of movement and understanding target species biology is critical in designing effective wildlife crossing structures. A community/ecosystem approach rather than species specific approach has been found to be most effective in maintaining habitat connectivity and ecological functions. Research has demonstrated that location is a critical aspect of design, particularly for low mobility species (e.g., small mammals, reptiles, amphibians). Geographic Information Systems (GIS) analysis can be used to determine the most valuable habitat for wildlife and wildlife movement by characterizing landscape features such as vegetation, riparian corridors, development, and topography.

To maximize the benefits of providing roadway crossings for wildlife for low mobility species. crossings should not be more than 500 feet apart. Crossings can be placed closer to each other if cost and context permit. For wildlife with large home ranges [e.g., bobcat (Lynx rufus), deer, moose, fisher (Martes pennanti)], crossings should be placed no more than one mile apart. Closer is preferred, if possible. For long projects, spacing should be prioritized according to habitat suitability and future potential development. Adding a variety of crossing structure types to a project is recommended to meet the needs of different species and species groups.

Wildlife Underpasses

Wildlife underpasses can be large or small, depending on the target wildlife species. They can take the form of amphibian tunnels, eco-pipes, wildlife culverts, oversized stream culverts, and extended bridge structures.

Underpasses targeted for a specific species group should be located and designed to accommodate their behavior and habitat needs. For example, migrating amphibians are hesitant to enter tunnels with a microclimate that is significantly different from their surroundings. Therefore, amphibian underpasses should be designed to minimize differences from surrounding levels of light, air flow, and humidity. Concrete tunnels are preferred over steel or plastic. Culverts should be at least 2 feet by 2 feet, and should be grated to allow ambient light, air and moisture to enter and pass freely through the tunnel. MassDOT has already incorporated these types of underpasses into projects, including an amphibian tunnel constructed beneath Henry Street in Amherst, Massachusetts to minimize roadkill of spotted salamanders as they migrated to and from breeding sites (see Figure 14-2), and another larger, 10-foot wide tunnel under Route 57 in Agawam.

Figure 14-2: Wildlife Underpass – Amphibian and Reptile Tunnel

Source: Tamara Sayre; used with permission from S. Jackson, UMass Amherst

Eco-pipes are small, dry tunnels (1-foot to 1.3-foot diameter) used to facilitate movements of small and medium-sized mammals. They have been installed in the United Kingdom and the Netherlands and appear to be successfully used by badger (Meles meles) and otter (Lutra lutra). Wildlife culverts are similar to eco-pipes but are installed in conjunction with hydrological features. They are up to 4 feet wide and have raised dry ledges, or shelves, on one or both sides of the waterway that allow wildlife to cross under the road and adjacent to the river or stream. The shelves also ensure that the appropriate stream channel configuration is maintained, which prevents possible geomorphological streambank degradation. Dry drainage culverts have been used in Canada, the United States, Europe, and Australia. They are useful for small and medium-sized mammals, ungulates, and possibly reptiles. Dry drainage culverts can be constructed in uplands, particularly in areas of high-quality wildlife habitat or areas with nearby wetlands. Results of wildlife crossing monitoring highlighted the importance of dry drainage culverts for small mammal movement.

Oversized stream culverts or extended bridges are options during replacement culvert or bridge situations along waterways where target species include both upland wildlife and aquatic species (see Figure 14-3 and Massachusetts Stream Crossings Handbook). Extended bridges maintain terrestrial habitat connectivity by providing an unsubmerged area adjacent to the waterway. Abutments extend beyond water’s edge to provide a natural bank under the bridge—animals can cross under the bridge instead of over the road. Construction of a concrete shelf above the floodplain will encourage use by terrestrial species; care should be taken to not alter stream hydrology. Bankfull width must be maintained for the stream to continue to convey the appropriate water volume and bedload material (i.e., material transported by a stream).

Figure 14-3: Wildlife Crossings – Extended Bridge

Source: MassDOT

Wildlife Overpasses

Wildlife overpasses can be added to existing roadways, but do not piggyback onto existing roadway drainage features in the way that underpasses can; generally, they are standalone features built specifically and only for wildlife passage. Including passage options for people (hiking trails) or vehicles (roadways) severely limits their benefit and utility for wildlife.  Wildlife bridges over highways have been constructed in Canada and Europe with an excellent example constructed along I-70 Mountain Corridor in Colorado. They are generally only feasible and cost effective where substantial areas of high-quality wildlife habitat occur on both sides of the roadway and there are acute concerns for human safety and/or viability of wildlife populations. They are usually constructed at high points in the landscape over roadway to connect habitat, and naturalized with plantings of grasses, shrubs, and small trees.

Culvert Replacement and Stream Restoration

Replacing undersized culverts with bridges or “stream simulation” culverts can restore river and stream continuity and facilitate passage by fish and other aquatic organisms. Stream restoration may occur as part of a culvert replacement (to address scour or aggradation that may have occurred due to the undersized structure) or in other areas, such as eroding or previously riprapped banks or stream sections that were artificially straightened to accommodate a road or highway. The Massachusetts Stream Crossings Handbook contains discussion and guidance on stream simulation design, replacement structure alternatives, and stream crossing standards.

Modified Concrete Barriers 

Concrete barriers are concrete safety devices that are typically used on divided highways as a means of keeping two-way traffic separate or preventing access to a restricted area (e.g., during highway construction). When installed in the median, they may increase some wildlife mortality by trapping small- and medium-sized mammals. Concrete barriers have been modified (and are in use on Route 6A on Cape Cod and along sections of Route 24 and Route 3) so that “scuppers” allow for the passage of small species through the barrier and promote more efficient drainage. Concrete barriers can also be installed at the outer edges of a highway to keep wildlife off roadways.

Fencing

Fencing is a common practice used to keep wildlife off highways, but it must be regularly maintained to the highest standards to be successful. Gaps resulting from poor construction, erosion, or crawl holes dug by animals reduce efficacy, as wildlife will exploit fence gaps. For high-volume roadways, such as interstates, fencing should be considered as an exclusionary measure where WVCs with deer and moose are a safety concern. Exclusion fencing may also benefit small mammal populations by providing forage and cover habitat near highways. Additionally, for wildlife crossings (described below) to be successful, studies indicate that, in the areas adjacent to a crossing, the roadway must be fenced to direct animals to crossing structures and prevent them from crossing over the roadway instead. For deer, fencing should be at least 7 feet high (preferably 8 feet high) upright chain link “outrigger” fencing (sloped) to prevent deer from approaching close enough to jump over the fence.

For amphibians and reptiles, fencing can be constructed of silt fence, low-height chain link fence, concrete retaining wall, or other piped/bermed solutions. Installing silt fence is significantly less expensive than constructing a retaining wall but requires considerably more maintenance to be successful.

14.5 Summary

As described above, a variety of design options are available to incorporate wildlife accommodation into roadway repair and upgrade projects. Projects which include stream crossing and/or drainage and stormwater measures as part of reconstruction must also be consistent with guidance in the Massachusetts Stream Crossings Handbook.  When projects include stream crossings, the following measures should be considered:

• Culvert replacement – oversized and/or with a wildlife shelf
• Stream restoration
• Extended bridges

If projects do not include stream crossings, the following measures should be considered:

• Signage
• Public education and awareness
• Reduced speed limits
• Modified concrete barriers (on divided highways)
• Fencing
• Dry drainage culverts
• Amphibian tunnels

Existing Guidelines

In Massachusetts, there are published guidelines and manuals that focus on proper stream crossing installations, particularly culverts. Each is briefly described below.

Massachusetts Division of Ecological Restoration Stream Crossings Handbook

The Massachusetts Stream Crossings Handbook provides guidance on meeting the Stream Crossing Standards. Note that the Massachusetts Wetlands Protection Act (WPA; 310 CMR 10.00, June 2014) requires all new crossings to meet the Stream Crossing Standards and all replacement crossings to meet the standards to the maximum extent practicable.  

U.S. Army Corps of Engineers Programmatic General Permit Conditions

In April 2018, the U.S. Army Corps of Engineers (ACOE) reissued the Programmatic General Permit (PGP) for Massachusetts.

14.6 For Further Information

• Massachusetts Stream Crossings Handbook, MA Division of Ecological Restoration, 2012
• Linking Habitats and Reducing Roadkill, FHWA, 2002
• Massachusetts Wildlife Habitat Protection Guidelines for Inland Resource Areas, Massachusetts Department of Environmental Protection, 2006

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