Transportation planners know building more car capacity causes more driving. Growing evidence shows the amount of miles driven, not congestion, is the major factor in greenhouse-gas emissions and vehicle crashes. Indeed, California has mandated VMT analyses for its environmental analyses and discounts congestion delay as an environmental measure.
Here's what really happens when we widen a congested road. In the short term:
- some drivers who avoided the congestion by using parallel roads will use it,
- some drivers who delayed their trip will no longer delay their trip, and
- some drivers who skipped their trip completely will now make it.
In the long term:
- some drivers will travel farther for trips or live farther away, and
- some cyclists, walkers, transit users will drive; some will need to buy a car.
As has been proved time and again, road widening does not relieve congestion — it just raises the number of vehicle miles traveled, a phenomenon known as "induced demand." The model's underestimation of induced demand for widening I-5 in the Rose Quarter — hidden in the environmental assessment's appendix — is 5,770,395 more vehicles miles traveled annually by 2045 in the immediate area, and there will more outside this area.
The Oregon Transportation Commission will ultimately decide whether the I-5 project goes forward without a full Environmental Impact Statement. Unfortunately, the OTC just hired a director who believes in the "alternative facts" that widening roads relieves congestion and is good for the climate and crash rates. The writing is on the wall.