Photo by Mrs. Gemstone on Flickr.

Virginians have debated widening I-66 for many years, but preliminary results of a VDOT study show that I-66 commuters could get the same benefits and save hundreds of millions by just converting existing lanes to HOT lanes instead. Drivers and transit riders alike would also benefit from turning the shoulder of US-50 into a dedicated bus lane.

VDOT is close to completing its “multimodal” study of the I-66 corridor inside the Beltway. The study team looked at a wide variety of options, from Metro to buses to adding lanes to Transportation Demand Management (TDM) strategies like better rider information and dynamic ridesharing.

The full study isn’t out yet, but VDOT has released information on four “packages” of improvements they modeled:

  1. Make both lanes of I-66 free for buses and HOV-3 at all times, and toll single-passenger vehicles (SOV) and HOV-2 at all times.
  2. Add a 3rd lane to I-66. Make all 3 free for buses and HOV-3, tolled for SOV and HOV-2 at all times.
  3. Add a 3rd lane to I-66 to be HOV-2 in the reverse peak. In the peak direction (eastbound mornings, westbound evenings), keep all lanes HOV-3. Off-peak, leave all lanes open to anyone (as they are today).
  4. Make the shoulder of US-50 into a bus lane. Add express bus service to downtown DC from places along the I-66 and Dulles corridors.


All of these assume that Virginia has finished all of the projects in the existing Constrained Long-Range Plan (CLRP). That includes the so-called “spot improvements” that widen I-66 in select places, and also converting I-66 to HOV-3.

Packages 1 and 2, the HOT lane options, both would help SOV and HOV-2 drivers and hurt HOV-3 drivers, compared to the default of having I-66 be HOV-3 only. But there’s not a whole lot of difference between the two. According to the model, having the extra lane would slightly harm transit and speed drivers by about 2%, at a cost of $310-685 million.

Package 1 (convert existing lanes to HOT lanes):

Package 2 (add 3rd lane, convert all to HOT lanes):

Package 3 induces more driving but doesn’t do much to change travel times for anyone. Package 4, the US-50 bus lanes, would improve travel times on transit by 7%, and drivers benefit by a very small amount. The presentation says that a number of people switch from rail to bus because the buses improve, which should also help with crowding on Metro.
Package 3 (add HOV lane):

Package 4 (bus lane on US-50):

The packages also factor in projects like better bicycle and pedestrian facilities, TDM programs, Integrated Corridor Management (ICM) like digital signs and ramp meters, added bus service and more.These graphs are all a tiny bit confusing because VDOT assumed as the “baseline” that I-66 has changed from the current HOV-2 to HOV-3, and that they’ve already widened in some places with “spot improvements.”It would have been more helpful for laypeople if we could also compare each alternative to what would happen if VDOT didn’t build the “spot improvements” and didn’t change to HOV-3. In fact, an initial impetus for this study was to find out whether the spot improvements are a good idea in the first place, or whether other options would work better.VDOT will release the study, including more details and its recommendations, in June. It seems unlikely that they would recommend widening I-66 given these results. A combination of options 1 and 4 seems like it could deliver real improvements to both drivers and transit riders without spending a lot of money on complex, unpopular, and minimally helpful highway widening projects.Residents can provide comments to VDOT by emailing info@i66multimodalstudy.com.Update: The original version of this post showed incorrect graphs for packages 2 and 3. The graphs have been corrected to match those from the VDOT presentation.

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David Alpert is the founder of Greater Greater Washington and its board president. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.