Transforming freeways into high-performing multi-modal corridors:

For decades, government’s knee-jerk response to the problem of congestion on America’s freeways was to build more lanes. Unfortunately, a phenomenon known as induced demand perpetuates an unending cycle of road widening, exemplified vividly by Houston's 26-lane Katy Freeway (pictured below).

Initially expanded in the early 2000s to ease congestion, the addition of more lanes led to increased traffic volume as drivers adapted to reach newly developed suburban areas. This surge overwhelmed the widened road, leading to renewed congestion. In response, authorities undertook further expansions, bringing more cars onto the highway, perpetuating a costly cycle of road widening. This shows induced demand's insidious nature; by accommodating increased traffic, new freeway lanes stimulate more driving, exacerbating urban sprawl but not actually “solving” the problem of congestion that was the initial impetus for adding lanes.

In some parts of the US, transportation planners learned about induced demand as early as the 1980s and 1990s, and for the most part, put the brakes on building new freeways. They came to realize that money spent reducing demand for roads and encouraging the use of alternative travel modes such as transit, walking and biking was a better investment than attempting to satisfy the endless public demand for new pavement.

Planners in other parts of the nation, however, responding to pressure from suburban residents and their elected representatives, continued to “build baby build” in a futile attempt to stay ahead of ever-growing demand for freeway road space. As federal money for large-scale freeway expansions dried up, many regions turned to public-private partnerships and tolling to fund new capacity for cars and trucks. Often such projects included high-occupancy and/or tolled lanes alongside general-purpose lanes for the stated purpose of reducing congestion.

Although such “managed” lanes, including HOV (High Occupancy Vehicle) and HOT (High Occupancy Toll) lanes may blunt the worst aspects of peak-hour congestion, they have not resolved the problem of freeway traffic congestion.

Here’s why: Whenever highway capacity is increased, even if the added capacity is tolled, the “price” paid by travelers in regular lanes in terms of travel time declines as some traffic shifts to the new lanes. When the price of auto travel decreases, demand increases, following the law of supply and demand. Additionally, the eligibility criteria for HOV lanes, requiring a minimum number of occupants in a vehicle, may not be practical or feasible for some commuters. Moreover, HOT (high-occupancy toll) lanes require the physical separation of lanes and costly flyovers so that drivers in the managed lanes can access freeway exit ramps. Overall, while HOV and HOT lanes offer partial solutions to congestion, they are not comprehensive enough to entirely alleviate the problem, especially in areas with high demand for road infrastructure.

Congestion pricing schemes like the program that’s about to launch in the New York region have proven successful at reducing freeway traffic in Singapore, Stockholm and Oslo. With all lanes variably tolled, such programs are more affordable to implement than HOT lanes. Because they eliminate free travel in (non-tolled) general purpose lanes, such schemes may be a tougher sell politically, particularly in fast-growing suburban areas.

SmartGO board member, Michael Replogle, and a group of allies have come up with a promising new approach to repurposing America’s congested freeway corridors. It’s called IC4M (Integrated Congestion and Multi-Modal Mobility Management). Building on a patchwork of existing and partially implemented managed-lane efforts across the US, IC4M takes a “complete-streets” approach to freeways by providing transit on the same or parallel routes and offering real monetary incentives for taking transit, carpooling, biking and traveling during low-demand periods.

We invite you to learn more about IC4M by reviewing the deck below and exploring the resources at the bottom of this page.

Additional Resources:

A great video from Vox explaining induced demand using the example of Houston’s Katy Freeway; “How Highways Make Traffic Worse”

Another video explaining induced demand from the acclaimed Not Just Bikes series by Jason Slaughter; “More Lanes are (Still) a Bad Thing”

An empirical demonstration of the effectiveness of managed lanes; “The Doug MacDonald Challenge - Rice and Traffic Congestion”

Michael Replogle’s narrated presentation on IC4M/Hotter Lanes (January, 2024; begins at 24:40) as an alternative to the possible expansion of I-495 and I-270 in the Maryland suburbs of Washington, DC

SmartGO’s NexTDM program summarized; This behavioral program is a key component of the IC4M program.

Integrated Corridor Management (ICM), an initiative of USDOT started in 2006, sought “to improve the movement of people and goods along metropolitan corridors through a multimodal, integrated transportation management approach.” Over time, the program helped to relieve episodic congestion from crisis events (such as an overturned truck blocking all lanes) but did little to reduce everyday traffic. An article from the March/April 2008 issue of Public Roads explains the concept.

Next Gen Policy’s report makes a strong statement about the need to limit VMT (vehicle miles traveled) growth; “California at a Crossroads - Unleashing Climate Progress in Transportation Planning.”

Precedent employing some features of IC4M: