The existing Arroyo Bridge is part of State Route 134 (the Ventura Freeway) at the western edge of Pasadena, California.  The bridge crosses the Arroyo Seco half of a mile from the mouth of the proposed 710 extension at the intersection of the 134 and the 210. Unlike the adjacent iconic Colorado Bridge, the Arroyo Bridge is a utilitarian highway designed to carry 10 lanes of vehicular traffic over the scenic Arroyo Seco landscape below.

The current condition of the 134 is at odds with its context, polluting the surrounding neighborhoods with noise and vehicle emissions and simultaneously eroding the Arroyo landscape  between the San Gabriel Mountains to the north and the Los Angeles River to the south.  The bridge spans over both natural and built spaces including the Arroyo Seco Hiking Trail, Lower Arroyo Park, the historic La Casita Del Arroyo, and the former Desiderio Army Reserve Center that is being transformed into new parkland and Habitat for Humanity homes.

This area is a year-round resource for residents and visitors but the design of the existing bridge prioritizes traffic efficiency at the expense of the health of the delicate ecosystem of the valley corridor below.  But what if we ask more of the Arroyo Bridge without compromising the integrity of the existing infrastructural efficiency?  What if the bridge became an experiential and aesthetic asset for residents and visitors? What if we demand that the bridge do more?


In 2015 MMA set out to rethink the Arroyo Bridge as a beneficial, living link across the city.  Instead of dividing the urban landscape, the bridge would fulfill a new vision of an infrastructural multiculture to support community building, mitigate environmental deterioration, and improve the architectural experience for motorists and pedestrians.

The Arroyo Bridge project imagines an “environmental machine” designed to enhance rather than replace the existing freeway.  We envision a design solution that celebrates the experience of driving over the Arroyo Seco while sustainably integrating the freeway into its immediate context.  Working in partnership with Arup Los Angeles to develop elements of this new infrastructural overlay, the project includes:

  • A design to celebrate the experience of driving over the Arroyo Seco while sustainably integrating the freeway into its immediate context.
  • Acoustically insulated walls added to the bridge to alleviate environmentally degrading noise with transparent panels at driver height to preserve views to the Colorado Bridge to the south and the Rose Bowl to the north.
  • An overhead canopy of photovoltaic panels and porous concrete ‘lungs’ that utilize photocatalytic concrete to filter automotive emissions from cars on the bridge to improve overall air quality.
  • Green walls to drape the exterior of the added structure irrigated exclusively by storm water captured from the bridge canopy.
  • Rainwater collection and storage connected to the Pasadena water supply during droughts or used to recharge the Arroyo Seco riverbed.


As an approach to infrastructure, these types of enhancements are not specific to the 134, but are expandable to other freeways. Future partnerships among transportation agencies, local municipalities, and state agencies could be formed to rethinking the fundamental role of infrastructure in the city.  These collaborations could lead to long-term environmental, social, and cultural improvement strategies.

A symbiotic relationship between regional and local needs, infrastructural design could become both an investment in local education and a conduit for environmental change. For example, the energy produced by the Arroyo Bridge could be fed into the Pasadena Department of Water and Power; the energy cost savings could in turn be directed to the Pasadena Unified School District, specifically the six elementary and high schools within two miles of the bridge.  This is just one instance of how we might implement this strategy as a prototypical condition for infrastructural redevelopment.

The Arroyo Bridge project anticipates a change in how the city can relate to its freeways and requires infrastructure to perform better for its context. By supplementing the vehicular network, a vision for the future of freeways embraces existing connectivity with newfound environmental sensitivity.

TYPE / Innovative Infrastructure Research
LOCATION / Pasadena, California
STATUS / Research Completed 2016
ROLE / Design Architect
PROJECT PARTNERS / Arup Los Angeles, Engineering