The State We're In

Tunnel vision: helping wildlife cross the road

Feb 20, 2020

Why did the turtle cross the road? Probably to look for a place to lay her eggs.

The better question might be: Can she get to the other side? The answer: Only if she’s lucky.

New Jersey’s vast network of roads with high-speed traffic can be dangerous for small, slow-moving reptiles like turtles and snakes – and for amphibians like salamanders and frogs, and mammals of all sizes. Critters don’t do well with cars.

Fortunately, customized wildlife crossings are under way in several key places in this state we’re in.

For example, five “turtle tunnels” were completed in Bedminster Township, Somerset County, in 2015 – the first of their kind in the state. The tunnels go under busy River Road, which separates the North Branch of the Raritan River from hundreds of acres of natural area and parkland. Fencing to guide animals into the tunnels was part of the project.

The tunnels help wood turtles – a threatened species in New Jersey – move from hibernating areas in wetlands along the river to spring breeding grounds on the other side of the road.

According to follow-up studies by Montclair State University, the tunnels are also helping other species, including snakes, frogs, toads, salamanders, newts and box turtles. Even small mammals like raccoons, foxes, moles and voles are using them. Up to 150 animals per days have been spotted using the tunnels at the peak of spring migration.

The success of the Bedminster tunnels led to a similar project at the Assunpink Wildlife Management Area in western Monmouth County. Two tunnels now reconnect fragmented patches of wetland habitat, providing a safe way for animals to move between the wetland areas without touching pavement.

Other projects under way, but not yet built, include tunnels under Waterloo Road in Byram Township, Sussex County, near the Musconetcong River.  Every spring, thousands of frogs, toads and salamanders awaken from hibernation and cross the road to breed in vernal ponds.

“It’s by far the largest number of animals that we know of (crossing a road) in New Jersey. It’s really extraordinary,” said Brian Zarate, a biologist with the state’s Endangered and Nongame Species Program.

For years, dedicated volunteers have helped amphibians cross Waterloo Road during the busiest migration nights. But volunteers can’t always be on hand when warm rains trigger a mass migration. Tunnels are considered the best permanent solution.

Bedminster, Assunpink and Waterloo are all classified as priority sites for critter crossings by a statewide project called “Connecting Habitat Across New Jersey.”

“Animals need to be able to move through the landscape to find food, shelter, mates, and other resources,” according to the project’s guidance document. “Without that ability to move, healthy populations simply cannot persist over the long term. Here in New Jersey, wildlife are up against steady urbanization, a dense network of roads, and now a changing climate, all of which put the connectedness of our habitats and wildlife populations in jeopardy.”

The goal of Connecting Habitat Across New Jersey is to make the state’s landscape and roadways safer for wildlife.

Installing tunnels under roadways can be expensive, so some projects use existing drainage culverts under highways. Motion-activated cameras at a sampling of culverts showed that animals already use them to avoid roads and traffic. A well-known shot shows a bobcat emerging from a culvert in Sussex County several years ago.

The problem, said Zarate, is that some animals don’t like to get their feet wet, so they’ll avoid culverts with water. One solution is to provide elevated areas, or “shelves,” within culverts. In one successful project along the Atlantic City Expressway, rock-filled wire baskets known as gabions were placed in the culvert and topped with plywood and mulch.

The oldest and best known New Jersey wildlife crossings are the bridges built during the construction of Interstate 78 in Union County the 1980s. The bridges look like ordinary highway overpasses, but they’re covered with trees and bushes instead of asphalt.

The wildlife overpasses were designed in response to plans for I-78 to bisect the Watchung Reservation, nearly 2,000 acres of natural parkland. Although the highway was eventually rerouted closer to the reservation’s northern border to reduce impacts on the park, the overpasses were still built.

“That’s a really interesting project to us,” said Zarate, noting that they were the first wildlife overpasses in the United States. However, he said, there are “some fairly glaring errors in design,” such placing them too close to local roadways that are crossed by animals.

While there’s evidence that the I-78 overpasses are used by raccoons, foxes, deer, skunks, possums and squirrels, Zarate said they probably wouldn’t be built in the same locations today. Similar overpasses in the western U.S. are built only where they connect undeveloped pieces of land, he said.

New Jersey’s efforts to provide safe road crossings for wildlife – especially our rare and endangered species – are exemplary and a wonderful model!

To learn more about Connecting Habitat Across New Jersey, go to The website includes an interactive map where you can click to see “road wildlife mitigation projects.”

And for information on preserving New Jersey’s land and natural resources, visit the New Jersey Conservation Foundation website at or contact me at



About the Authors

Alison Mitchell

Co-Executive Director

John S. Watson, Jr.

Co-Executive Director

Tom Gilbert

Co-Executive Director, 2022-2023

Michele S. Byers

Executive Director, 1999-2021

View their full bios here.


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