The Answer for I-35 is Understanding a Different Geometry

Written by Sinclair Black FAIA

The numerous failures of the U.S. urban freeways are by now clearly documented. From the racially motivated location decisions of the 1950s all the way to present-day bogus modeling projections. The failures continue in the complete absence of any attempt to meaningfully address environmental concerns, including air pollution, noise pollution, and climate change. Even “safety concerns” are used as an excuse to widen all roads, but there is never any evidence of achieved safety, only wider roads with cars traveling at increased speeds and continued unacceptably high rates of deaths and serious injuries on highways. This is outdated geometry required by federal policy and engineers that prioritize speed over human life.

This outdated geometry includes total isolation of the highway in order to maintain high speeds, super long high-speed ramps, and frontage roads. This is clearly the formula DOT uses, which works ONLY for car traffic with total disregard for the city and its citizens.

Imagine a different geometry that buries the main lanes and the frontage roads and transforms the land consumed by the frontage roads to create a boulevard directly on the cap in the same footprint. By doing this, two kinds of truly safe access are created:

  1. The boulevard used for short, local trips, creates a typical city experience.
  2. The portal ramps are used to enter and exit below ground. The shorter ramps reduce speeds overall by using lower speed collector-distributor (CD) lanes and create a safe entry/exit experience.

To fully understand “THE BARRIER EFFECT” one only needs to look at the existing highway system and notice the number of layers of barriers:

  1. The long high-speed ramps that cut the city off from any east/west connections.
  2. The frontage roads are also a significant barrier, even where there are no ramps.
  3. The highway itself is a barrier, whether it is elevated or depressed.

There are 7 simple changes to geometry that need to happen in order to achieve safety, prosperity, and a great quality of life within the corridor:

  1. Sink the main high-speed lanes and cap the sunken highway to mitigate damage to the city and control pollution.
  2. Combine collector-distributor lanes and portal ramps to ensure safe access from the corridor into the city (instead of frontage roads).
  3. Ensure direct access to East/West destination streets with portal ramps.
  4. Use collector-distributor lanes, at lower speeds, to allow traffic to emerge onto East/West city streets a block away from the boulevard edge, where all of the value is created.
  5. Intentionally employ this new geometry, which creates a separation between local access and long- commutes.
  6. Recognize that the boulevard represents one form of safe access and the portal ramps another.
  7. Establish a design-based development commission to oversee all future re-development of the entire corridor funded by Tax Increment Financing (TIF) and by private investment.

These simple, logical geometric changes preserve the vast economic potential of the corridor. Without these logical geometric design choices, we face a wide range of missed opportunities.

This op-ed can be downloaded here.