February 12


Top Seven Benefits of Converting One-Way Couplets to Two-Way Streets

By Mike Spack

February 12, 2015

1 way to 2 way street, benefits of, conversion, couplets, one way to two way street

Based on this summary of academic work by Dr. John Gilderbloom, converting one way streets to two-way streets improves the livability in neighborhoods by:

  1. Reducing Crime
  2. Reducing Collisions
  3. Increasing Property Values
  4. Increasing Business Revenue/Taxes
  5. Increasing Bicycling Traffic
  6. Increasing Pedestrian Traffic
  7. Increasing Vehicle Circulation

Dr. Gilderbloom’s research is consistent with Minneapolis’ experience of converting the Hennepin Avenue/1st Avenue couplet to two-way flow (read here).  Minneapolis traffic engineering staff was very skeptical of the conversion because they thought traffic flow would be significantly degraded by the conversion to two-way.  To their credit, I’ve heard them say they were mistaken and traffic flow was not noticeably hampered by the conversion and the benefits to safety, circulation and bike flow have made the conversion a success.

I believe there is still a place for one way couplets in Central Business Districts, but many of the one-way couplets in our cities should be converted to two-way operations.  Traffic modeling should be done of future operations when conversion projects are considered, but the evidence seems to point to the conversions almost always being a good idea.

Mike Spack Bio

  • .Dear Mike,

    Thanks for the information on the 7 benefits for converting one-way street into two-way street.

    I agreed to all the benefits from this conversion as the case in Hong Kong. But, can you further elaborate how this conversion can reduce crime? Thanks


  • Reducing crime was a finding of the underlying academic work. I imagine that is a byproduct of having a stronger neighborhood along the street.

  • You attribute all of these benefits to the conversion of one-way to two-way, but in fact they have little if nothing to do with one-way or two-way. The benefits you and others are seeing come from the design: reduced the speed limit (and/or design the reduces driver’s tendency to speed), as well as major investments in amenities and streetscape. That’s what encourages private investment. The underlying presumption of all who claim two-way is better than one-way is that one-way streets are inherently “fast and furious” to quote from Dr. Gilderbloom. But the natural speed drivers will gravitate to has virtually nothing to do with one-way or two-way. It is a function of lane widths, on-street parking, visibility, posted speed limit, visual cues, and density of multi-modal activity.

    In fact, one-ways with frequent signals have a major advantage over two-ways in getting drivers to adhere to the posted speed limit – the fact that they’re easy to synchronize. If a two-way street is posted 35 mph, many drivers will drive 40-45 knowing they’re unlikely to get a ticket. But a one-way posted at 35 can get drivers to average exactly 35, because when they see signals turning green “like falling dominoes” set to 35 mph, they quickly discern there is no advantage to driving faster than 35.

    Is it true that many older couplets are fast and furious? Sure – just as many two-way streets created by yester-year’s traffic engineers are fast and furious. But to compare an old, decaying couplet which is still fast to a converted two-way which is now slower and had major amenity investments is like comparing apples and oranges. What if they had made a similarly major streetscape investment around the couplet framework, and created a design which would require drivers to slow down? Good chance these seven benefits would have also been realized.

    Couplets have higher vehicle capacity, but that need not mean they are “auto-oriented.” There are hundreds of examples in high-density downtowns where low-speed couplets blend in well with everything else. While I am clearly a fan of couplets, (search my “Top 10 Advantages of one-way couplets at http://www.MetroAnalytics.com), I am certain that in many cases converting back to two-way will not be a problem and could be the right thing to do. Such cases include dying downtowns where one street is a historic Main Street, and the other has never developed much commercial. In cases like that it could be good for add volume and visibility back to Main Street with a two-way. But it is a mistake to assume that conversions are “almost always being a good idea” as you seem to conclude. In corridors with high traffic volumes, or where the community has hopes of intensifying development, conversion could be a costly mistake. I suppose you could argue it makes the area more “walkable” because the resulting congestion makes it impossible to get anywhere unless you walk. But there are better ways to create walkability that do a good job of integrating vehicles rather than penalizing them. Private investment thrives when all modes are working well.

  • {"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}
    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

    Get these blog posts sent to your email! Sign up below.