Alexander Road is closing for nearly six months, and officials are predicting traffic tie-ups for the Princeton area.

Alexander Street/Road in Princeton and West Windsor will be closed and detoured beginning on Wednesday, November 6, for concurrent Mercer County and NJ Department of Transportation bridge replacement projects. The detour route will use Washington Road, Faculty Road, and Route 1.

There are two separate bridge replacement projects involving three bridges near each other.

The NJDOT project will replace the bridge over the D&R Canal between Princeton and West Windsor, which was built in 1948 and is in poor condition.

The Mercer County project will replace two structures: the bridge over the Stony Brook and the Bridge over Alexander Creek, which are north of the D&R Canal.

To minimize the duration of the closure of Alexander Street/Alexander Road, all three structures will be replaced simultaneously. Both NJDOT and Mercer County say they are employing Accelerated Bridge Construction techniques for their respective bridge replacements, which should reduce the required closure time of Alexander Street. Conventional bridge construction would require approximately 9-12 months to complete. These projects are expected to be completed in less than six months.

Mercer County and NJDOT say they coordinated with regulatory agencies such as the New Jersey Department of Environmental Protection, NJDEP State Historic Preservation Office, D&R Canal State Park, D&R Canal Commission, NJ Water Supply Authority and stakeholders, such as West Windsor, Princeton, and Princeton University.

Construction schedules were largely driven by environmental restrictions. The projects are expected to be completed in the spring of 2020, with the detour removed by April 20, 2020.

Officials have given different timeframes for the project: The Town of Princeton said the project was scheduled to take four and a half months, while NJDOT gave a more pessimistic six-month estimate. During the closure Alexander Street/Alexander Road will be closed and detoured using the same detour listed above.

For the NJDOT Alexander Road Bridge over the D&R Canal, the towpath along the canal will be open during construction except during temporary closures for the safety of path users and construction personnel. However, pedestrians will not be able to access Alexander Road due to safety considerations as these areas will be active construction zones.

Commuters are encouraged to learn the multiple alternate driving routes and public transportation options that are available, and be prepared to try several options in the first days and weeks of the closure to find the route or mode of travel that best meets their needs while minimizing inconvenience. In addition, NJDOT is working to optimize traffic signal timing on Route 1 to assist with addressing traffic congestion where possible.

To mitigate congestion during this project, NJDOT has been working with local officials, employers, and commuters to promote several strategies including joining a carpool or vanpool, adjusting travel times to leave before or after the peak morning and evening travel periods, or to telecommute or work at other sites that employers may have available. NJDOT also recommends that commuters consider using mass transit.

Motorists will be encouraged to use alternate parallel routes, such as Route 27, Princeton Pike, and Route 206 if possible during the closure. Other routes that may be considered include Quakerbridge Road, Elm Road, Washington Road, Harrison Street, Witherspoon Street, and River Road.

The existing bridge over the D&R Canal consists of a three-span, simply supported, timber stringer-type bridge with a timber deck overlaid with asphalt. There is a six-foot-wide timber sidewalk on each side with continuous, rolled steel beams below. The existing structure features one travel lane in each direction and no shoulders.

The new bridge will be a single-span consisting of a beam-supported concrete deck on reinforced concrete abutments. The outer edge of the structure and concrete wingwalls will feature a wood facade. Bridge railings and guiderail will meet current standards and the design is respectful of the historic nature of the D&R Canal and surrounding area. The new roadway will consist of two 12-foot lanes, two five-foot shoulders and two five-foot wide timber sidewalks with concrete curbs.

The existing truss bridge over the Stony Brook was installed in 1989 as a temporary replacement to the structure in place at the time. Construction of a permanent bridge has now become a priority as the truss bridge has begun to deteriorate and the width is not adequate to accommodate bus and truck traffic.

The county says bridge railings and guiderails will meet current standards and the design is respectful of the historic nature of the D&R Canal and surrounding area.

The bridge just north of Basin Street over Alexander Creek also will be replaced due to deteriorated structural conditions. Both bridges will be built with the same roadway configuration as the new D&R Canal Bridge being constructed by NJDOT.

To assist motorist in choosing an alternative route, NJDOT will provide 11 message boards with travel times to and from Princeton via a variety of alternate routes. The boards will be located on Route 1, I-295, Route 206, Princeton Pike, Alexander Street and near the Princeton Junction train station. Real-time information on traffic conditions is always online at

For information on alternative travel options, ride sharing, telecommuting, and flex hours, visit the Mercer County Transportation Management Association at

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