The Tappan Zee Bridge forms part of I-287, a critical transportation corridor immediately north of Manhattan that links New York City to New Jersey and beyond. As the region’s primary east-west crossing, the route has been a catalyst for regional development since the 1950s.

Arup helped New York State plan the regeneration of the 30-mile thruway linking New Jersey to Westchester County, with the future development of the metropolitan area north of New York heavily dependent on the outcome of this project. 

The bridge carries approximately 135,000 vehicles a day, with traffic far exceeding the flow anticipated when the bridge first opened in 1956.

The first major transportation design/build project in New York State

There were several options under consideration for the future of the Thruway, including rehabilitating the current bridge, replacing it either with or without new commuter rail and/or bus rapid transit, or creating new tunnels under the Hudson River. 

Comprehensive analysis for a major thoroughfare

We took a wide perspective of the risks and benefits of the options available, investigating multiple aspects of the corridor. Our research included vulnerability, environmental concerns, risk and security analysis. To reach a conclusion on the best way forward for New York State, we used a wide variety of our core services. 

These included transportation planning, bridge and tunnel design, civil, structural, mechanical, electrical, geotechnical, highway, rail and seismic engineering, security, cost, fire/life safety consulting and transaction advice. 

We took responsibility for bridge inspection and testing, fatigue and seismic analyses, vulnerability and risk assessments, security, and rehabilitation cost estimation.

This comprehensive threat and risk assessment covered natural, accidental and deliberate threats. We calculated the probability and consequence of each threat to prioritise risks, then identified structural, operational and security countermeasures. 

Our security design team provided a security audit to identify pre-engineering design requirements (such as fencing and lighting) for both electronic and physical security. To make our findings clear, we facilitated a risk comparison exercise with the client and developed a risk/cost decision model.

Building consensus to build support

As project engineering support consultants, we also collaborated with stakeholders and the wider public to help achieve consensus for the way forward. Providing information on technical issues, we facilitated an extensive outreach effort, including meetings and workshops with local stakeholders and interest groups. 

The data gained from this process allowed our team to develop the preliminary design and output specifications for the draft environmental impact statement.

Technical advisory support for procurement

Arup provided integrated technical advisory support during the procurement process, incorporating constructability reviews with qualitative and quantitative assessments of the key project risks and mitigants. We advised on the development of a design-build procurement structure which we tailored to the owner’s resources and objectives, then managed the process to deliver commercial and technical expertise on a wide range of tasks, such as the establishment of an evaluation plan and selection criteria. This fast-tracked procurement resulted in New York State awarding us the contract just nine months after the RFQ release. 

Building a legacy in New York State

The client has been extremely pleased with our performance and contribution throughout the project. As Karen Rae of the New York State Governor’s office said in early 2012, “The team has worked hard to understand the goals and provide new solutions… this will be a legacy among projects in the US.”