By Barbara A. Preston | June 21, 2025
Just say the words "Griggstown Causeway" to a Montgomery or Franklin Township driver and be prepared for an earful. The road, also known as Route 632, is frequently closed when heavy rains cause the Millstone River to flood — which leads to major traffic jams in both towns, as well as Rocky Hill and as far south as Princeton.
The quaint, single-lane truss bridge over the Millstone is the scene of everything from road rage, as drivers from each side meet in the middle and refuse to back down, to traffic accidents. Recently, an 18-wheeler truck tried to cross, which has a posted weight limit of 5 tons (10,000 pounds).
The Griggstown Causeway Bridge in Montgomery Township, NJ. How could such a pretty, country bridge be a driver's nightmare?
Photo by Barbara A. Preston.
The weight restriction applies more to the to the causeway itself. The bridge actually is designed to handle truck traffic with no weight restrictions, however, the posting is for the causeway, which has hairpin turns making it nearly impossible for oversized vehicles to turn onto River Road in Montgomery, or onto Canal Road from the causeway.
Montgomery Township elected officials and staff members have advocated for significant improvements to address these safety concerns, according to Township Administrator Lori Savron. Somerset County officials are now studying the Griggstown Causeway, the bridge, and its surrounding area.
A map of the area to be studied.
The causeway connects River Road (CR 533) in Montgomery Township to Canal Road in Franklin Township and crosses the Millstone River, D&R Canal Park, and the Delaware and Raritan (D&R) Canal.
The study area includes the roadway network around the Causeway, including the following intersections:
River Road (CR 533) and Griggstown Causeway (CR 632)
Canal Road and Griggstown Causeway (CR 632)
Canal Road (CR 632) and Bunker Hill Road (CR 632)
Somerset County Bridge No. F0302, the one-lane truss structure that crosses the Millstone River.
Somerset County will host an in-person public information session on Tuesday, July 1, from 6:30 pm to 8 pm to update the community on the Griggstown Causeway (CR 632) Concept Development Study, which impacts both Montgomery and Franklin Townships. >> Click here to read the meeting notice.
When the Millstone River floods, the causeway and bridge can be closed for days.
Photo by Barbara A. Preston.
The meeting will cover the project’s goals and the Preliminary Preferred Alternative (PPA). Residents, business owners, and officials will have the opportunity to meet with engineers and consultants to ask questions and share feedback. The one-lane Griggstown bridge—Montgomery Township’s sole crossing over the Millstone River.
Date: Tuesday, July 1, 2025
Time: Doors open at 6:30 PM
Presentation: 7 PM
Q&A to follow
Location: County Administration Building, Commissioners Meeting Room, Third Floor
20 Grove Street, Somerville, NJ
Parking: Bernie Field Parking Deck (>>click here for directions.)
68 East High Street, Somerville, NJ
Park in the deck (Levels 2-6); Administration Building entrance is via the GREEN (2nd) level of the deck.
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To sign up for Somerset County Safety Alerts, including county road closures, go to: https://www.co.somerset.nj.us/about/emergency-alerts.
Below is a link to the National Weather Service (NWS) Gauge located at the Millstone River at Griggstown. The Griggstown Causeway is typically closed to traffic when the gauge reaches approximately 9 feet. Use of the NWS link is provided as guidance only. Timing of a road closure and reopening varies. Click here to view: https://water.weather.gov/ahps2/hydrograph.php?gage=gtnn4&wfo=phi
