Increasing Highway Capacity Unlikely to Relieve Traffic Congestion

[andy3175]

Found article from the National Center for Sustainable Transportation called "Increasing Highway Capacity Unlikely to Relieve Traffic Congestion." It appears on Caltrans' webpage.
http://www.dot.ca.gov/research/docs/10-12-2015-NCST_Brief_InducedTravel_CS6_v3.pdf

Reducing traffic congestion is often proposed as a solution for improving fuel efficiency and reducing greenhouse gas (GHG) emissions. Traffic congestion has traditionally been addressed by adding additional roadway capacity via constructing entirely new roadways, adding additional lanes to existing roadways, or upgrading existing highways to controlled-access freeways. Numerous studies have examined the effectiveness of this approach and
consistently show that adding capacity to roadways fails to alleviate congestion for long because it actually increases vehicle miles traveled (VMT).

An increase in VMT attributable to increases in roadway capacity where congestion is present is called "induced travel" . The basic economic principles of supply and demand explain this phenomenon: adding capacity decreases travel time, in effect lowering the "price"  of driving; and when prices go down, the quantity of driving goes up.

Induced travel counteracts the effectiveness of capacity expansion as a strategy for alleviating traffic congestion and offsets in part or in whole reductions in GHG emissions that would result from reduced congestion.

Commentary:
http://www.sfweekly.com/thesnitch/2015/11/18/caltrans-admits-more-roads-mean-more-traffic-and-your-commute-will-be-hell-for-all-eternity

Last month, Caltrans linked to a policy brief that sought to address whether more highways means less traffic congestion. Needless to say, the brief didn't go viral, but it's piquing curiosity as word gets out. Most state Departments of Transportation endorse the idea that building more roads spurs "economic benefits"  and relieves traffic, but California, as it often does, bucks that trend.

In fact, reducing road capacity tends to bring economic benefits without worsening traffic. The brief specifically calls out an example from San Francisco: "the removal of elevated freeway segments coupled with improvements to the at-grade Embarcadero and Octavia Boulevards,"  which revitalized the area while also relieving traffic.

According to the brief, much of the traffic on new roads is itself new. Some drivers ditch their old, slower routes for the new ones, while others are apparently cruising for the hell of it. After all, the "price"  of driving is lower when the state hacks out new highways.

[vtk]

I think people are drawing conclusions from these induced demand findings which are far broader than what the research actually supports. http://vidthekid.info/vspace/pt.php?bid=40

[The Ghostbuster]

If the increased capacity isn't congestion priced, it probably will eventually fill up, since demand will likely still outpace supply.

[Rothman]

If the increased capacity isn't congestion priced, it probably will eventually fill up, since demand will likely still outpace supply.

That's dependent on the area maintaining a level of growth, which is hardly guaranteed.

[The Ghostbuster]

I was refering to the most congested areas in an area's road system.