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Our transportation system and the communities that depend on it are facing serious challenges. People are stuck in traffic consuming oil, polluting the air, and wasting time. Our transportation infrastructure is aging and inadequate under the weight of increasing travel demand. Our auto-dominant transportation system becomes inefficient and ineffective during peak hours and emergencies—the times when it is needed most. Public transit is often too slow and limited in coverage to attract automobile users.

Working for the National Academies of Science, Dr. Ferrell has devleoped a new paradigm for planning, designing, building and operating multimodal corridors—freeways and high-capacity transit lines running parallel in the same travel corridors (hereafter called “multimodal corridors”). The new paradigm emphasizes building transit lines and supporting pedestrian and bicycle facilities with the following goals:

Enhancing corridor transportation capacity and performance without adding freeway capacity, by building and operating transit lines (including bus rapid transit, light rail, heavy rail and commuter rail).

Building and operating successful transit systems in multimodal corridors that attract high transit ridership and encourage livability and environmental sustainability.

Transforming a corridor’s land uses and activities to a more transit-oriented pattern.


The old paradigm developed transit lines to compete directly with their freeway neighbors for long-haul corridor trips and as a congestion reliever service. New paradigm multimodal corridors provide market segmentation—distinct, separated, and optimized travel markets for each mode—between the transit line and freeway.

Market-segmentation between transit and freeway is achieved using the following guiding principles and techniques:

Market-Segmented Transit and Freeway Designs (Multimodal Coordination): Station spacings and interchange spacings along each facility are designed to give each mode an advantage either in long-haul or short-haul corridor trips.  The new paradigm multimodal corridor offers the opportunity for each mode to thrive and potentially increases the total carrying capacity of the corridor.

Market-Segmented Urban Form Patterns: The new paradigm multimodal corridor encourages the development of separated, distinct land use and urban design environments for each mode within the same corridor. Transit station areas should have high-density, mixed-use, pedestrian-oriented land uses and urban design characteristics. Freeway interchange locations should have lower-density, separated uses with street designs conducive to smooth traffic operations and freeway access.

Market-Specific Station Access: Auto-oriented (called here, park-and-ride access) multimodal corridors focus on providing freeway-competitive transit speeds and prioritize auto and bus access to their stations. Transit-oriented multimodal corridors focus on maximizing transit line access to corridor land uses via nonauto modes while discouraging auto access.

Market Segmentation through Constrained Freeway Capacity: While often politically unpalatable, a number of multimodal corridors have developed divided travel markets by constraining the capacity of the freeway. Putting a low ceiling on the carrying capacity of the freeway gives the transit line an operational advantage, particularly for long-haul corridor trips.

Coordinated and Distinct Intermodal Operations:
The new paradigm incorporates two approaches to maximize interoperability between the transit line, the freeway facility, feeder bus lines, and pedestrian and bicycle facilities.

Intermodal Connections Limited to Key Locations: The new paradigm corridor encourages intermodal transfer stations—where park-and-ride lots, bus transfer facilities, nearby freeway interchange ramps, and cross-corridor pedestrian and bicycle route facilities encourage intermodal transfers—to be built at end-of-the-line (terminal) locations and key midline locations.

Intermodal Intelligent Transportation Systems: Intermodal transfers between freeway and transit can be facilitated and encouraged by real-time traveler information systems that provide information on corridor traffic conditions (congestion and incidents), transit schedule and schedule adherence, comparative corridor travel times (freeway versus transit), and station and destination parking availability and costs.


Based on our TCRP H-36 research (see the Project Work section of this website), CFA is currently defining the next stages of this research and associated tool development. We are pursuing the following initiatives:

Building the Evidence

CFA is currently developing the next phase of this research to help us understand the intricacies of how multiomdal coordination, market-segmented urban form patterns, market-specific station access, and other corridor factors affect mode choice, trip generation, and other travel behaviors.

Tools Development

Based on the research described above, CFA is currently defining a set of design, planning, and engineering tools that will help analysts create cost-effective and community-enhancing multimodal corridors.