U.S. Route 46 Rockfall Protection Fence

Improving Public Safety along Rockfall Prone Highway
Knowlton, New Jersey

The U.S. Route 46 Rockfall Protection Fence, the first of its kind in design and scale, will improve public safety by preventing rockfall onto U.S. Route 46. The $15.3 million fence spans between mileposts 1.4 and 2.4 in Knowlton, New Jersey. We collaborated with IH Engineers to analyze alternatives to address rockfall through the one-mile corridor.


mile corridor of rockfall protection

We performed geotechnical and geological investigations to establish the design criteria of the fence. Based on the subsurface conditions, proximity to U.S. Route 46, and economic analysis, we recommended drilled shafts for the foundation type that would support the steel fence posts. The team created a custom designed protection fence because the typical prefabricated rockfall catch fences were not suitable to protect against the magnitude of the rockfall. This custom designed fence is the first of its kind to be engineered and constructed by the New Jersey Department of Transportation and is intended to be a template for future projects with the same design conditions and magnitude of rockfall.


New Jersey Department of Transportation


New Jersey’s Leading Infrastructure Award

New Jersey Alliance for Action

Square Footage

4-foot wide rockfall catchment


$15.3 million


  • Engineering
  • Geospatial, Mapping and Survey
  • Planning, Consulting and Advisory


  • Transportation


  • Northeast