Guest post: Kurt Nordback on Bike and Walking Under/over-passes: Separate but Equal

Last week I reported favorably on the new underpass being finished in Boulder. Here is another take on under/over-passes, in general, by Kurt Nordback (, a software engineer who also likes to think about urban design and transportation policy.


PICT1209.JPGTransportation engineers like to solve traffic problems using engineering solutions, meaning building things out of concrete and steel. That’s in their training and in their nature. In general, they prefer the “hard” approach of physical structures to “soft” solutions based on psychology and subtleties of human behavior.

In the US, for the past 50 years or so that has worked well, thanks to two factors: flush transportation budgets with plenty of room for expensive construction, and policy that equated “transportation” with “motor vehicles”. There’s psychology involved in engineering roadways for cars, to be sure; but cars are hard objects and they respond well to hard solutions.

So when roads intersect, the natural engineering response is to want to separate them vertically, eliminating both “delay” and any chance of T-bone crashes. When roads intersect bike-ped paths, engineers want to physically separate the cars from the people. Thus are born underpasses and bridges.

This separation of modes dates to the early stages of Modernist planning philosophy. Pedestrian underpasses were built in an early “Garden City”, Radburn, NJ, tellingly dubbed the “Town for the Motor Age”. Subsequent suburban developments across the country, inspired by Modernist ideas, also built underpasses or bridges, often with stairs or ramps to get people from their natural ground level to a level where they wouldn’t interfere with the roads.

Which brings us to the doctrine of “separate but equal”, which was used for decades to justify separate and unequal facilities for whites and blacks. The analogy only goes so far — there’s a categorical difference between unequal treatment based on skin color and unequal treatment based on modal choice — but, within its limits, it’s instructive. At any grade-separated crossing, cars go nice and straight, staying pretty much at ground level. People, whether as pedestrians or bicyclists, go up or down stairs or ramps, and around loops or curlicues. Cars get to go fast; people are hidden below ground or up high. The engineers justify this in terms of cost — it’s cheaper to build a big ramping loop for bikes than for cars — but that doesn’t change the fact that the treatment is unequal.

In 1954, the US Supreme Court finally saw through the lie of “separate but equal” in its decision in Brown v. Board of Education. Coincidentally, just three years earlier Jane Jacobs had published her critique of Modernist planning, The Death and Life of Great American Cities. Jacobs did not speak to underpasses, but her embrace of robust urbanism and design that engages people in the active street life of the city leave little doubt as to how she would view them. The urban planner Jan Gehl, who follows in Jacobs’ footsteps 50 years later, has this to say about underpasses in his influential and insightful book, Cities for People: “Seen in the perspective of current visions of inviting people to walk and bicycle more in cities, clearly pedestrian underpasses and bridges can only be solutions in those special cases where major highways must be crossed. Solutions must be found for all other roads and streets that allow pedestrians and bicycles to stay on street level and cross with dignity…. Today the world is full of abandoned pedestrian underpasses and bridges. They belong to a certain time and a certain philosophy.”

Underpasses and bridges disengage pedestrians from the urban sphere, and hide them from the view of motorists. They are appropriate in certain circumstances, such as where an interurban path crosses an interstate highway, and also along greenway corridors, where path users are already intentionally disconnected from the city around them. But where they’re used just to get non-motorists across a city street, they are symptomatic of a less-than-wholehearted embrace of multimodalism, a clinging to the failed precepts of Modernism. The engineer may object that there’s no safe way for pedestrians to cross a high-speed road in the city, but the real question should be: what is a high-speed road doing in the city?

Moreover, the enormous cost of an underpass, in a time of declining transportation budgets, means forgoing lots of other, cheaper facilities. Boulder is in the midst of construction of an underpass costing $3-4 million, as part of a larger $7.4 million project. That much money could build a lot of sidewalks, refurbish a lot of bus shelters, plant a lot of street trees.

The better alternatives to grade-separated crossings are traffic-calming, road diets, reconnecting the street grid, allowing full movement at every intersection, and putting sidewalks on every street.

The Town for the Motor Age ushered in underpasses as a transportation tool; Cities for People deprecates them. The contrast is stark, and the conclusion is clear: though underpasses and bridges are nominally for pedestrians and bikes, their design comes out of an auto-oriented Modernist mindset. They are separate, but not equal, and urban design is best served by changing that mindset.



Cycling on busy roads and concentrated auto exhaust

I received the following email inquiry this morning:


Mr Krizek,

Some have questioned the wisdom of promoting bike use on roadways especially very busy ones or at busiest times because of the health hazards of heavy breathing in concentrated auto exhaust.
What can you say about that?

Here is a response, fresh off the press from the book recently edited by John Parkin of the UK:

Kevin J. Krizek (2012). Cycling, Urban Form and Cities: What Do We Know and How Should We Respond? Cycling and Sustainability; Transport and Sustainability, Volume 1. John Parkin, editor. Chapter 5; 111-130. Emerald Group Publishing, UK.

…from page 121

“Some recent research on cycling aims to better understand unintended consequences linked with increased exposure to air pollution (Panis, 2011; Zuurbier et al., 2010). Despite the many virtues of cities for cycling, including relatively high land use densities, a drawback to cycle use is related to air quality and this becomes more important when the activity in question requires significant amounts of oxygen intake. Air pollution can affect the respiratory system because of the deep draw down of air into the lungs and may even lead to heart rate variability (Weichenthal et al., 2011). Of particular concern are ultrafine particulates. Hazards from air pollution are extremely localized and require close proximity (a very few metres), which is just the position of cycle traffic in relation to localized air pollution problems caused by motor traffic. Various treatments have been proposed such as separating cycle traffic from motor traffic by more than the requisite distance, allowing and encouraging bicycles to wait for a traffic signal green light in front of the queue of motor traffic (in so-called bicycle boxes or behind so-called advanced stop lines, which also then have the advantage that they allow cycle traffic a head start before motor traffic accelerates from a stop), or, through appropriate area wide traffic management to create a tiered system of routes with cycle traffic and motor traffic encouraged to use adjacent parallel routes. Overall, however, the evidence suggests that there are potential consequences to cycling in urban areas dominated by motor traffic that need to be addressed in order to avert the potential for cycling in cities being increasingly associated with health risks (Zuurbier et al., 2010).”

Uptick in cycling research

Over the past few years, I’ve mentioned how there seems to be more than a general uptick in cycling-related “activity” out there. More coverage in the NY Times; more cities paying attention to cycling; more sales for bikes that allow us to get around town; more politicians mentioning bicycling as a platform; and, more academics studying elements of cycling. The list can go on.

These activities–and the corresponding uptick in academia–are reflected in the recent article in Pacific Standard. 


Plan Boulder County Presentation

This coming Monday, I will be speaking at Plan Boulder County.

How Green is Boulder’s Land Use Transportation System?

30 Jul 2012, 7:00 PM – 9:00 PM. Location: Shine, 2027 13th Street

A Report on the State of the Community and Future Challenges – Kevin J. Krizek
Kevin J. Krizek is Professor of Planning and Design at the University of Colorado Boulder where he also wears a variety of other hats, including:

-Director of CU Sustainability Research and Education;
-Senior Transportation Fellow for the Environmental Center;
-Co-Director, Active Communities/Transportation Research Group;
-Founding co-editor of the Journal of Transport and Land Use.

His research and teaching interests integrate transportation and land use. Krizek has been the Principal Investigator for close to $3 million of externally funded research; much of this activity focuses on transit, walking and bicycling. All of it aims to shape national policies on land use/transportation and advance local and regional planning efforts that further sustainable infrastructure. For example, the Design for Health project (; US APA’s National Planning Excellence Award for Best Practice) developed health impact assessments, research briefs and other tools for planners to assess policies. A report recently released by Kaiser Permanente documents a research and outreach project to identify a set of robust, consensus indicators for measuring Active Transportation in Colorado.

Krizek moved to Boulder in 2007 after serving on the faculty at the University of Minnesota in the Twin Cities. He lives on the Hill with his wife and 6 year old son and blogs at

Biking in London as an Olympic Sport

The 2012 summer Olympics are less than a week away. Read here to learn about and why London’s cycling culture bikesharing scheme might be comparable to an Olympic sport. According to the author, “nowhere else is a cycling culture so cutthroat, vicious, reckless, hostile, and violently competitive as London’s.”

Boulder’s lavish new Broadway Bike/Ped Underpass

Intersections are the source of more than half of all conflicts between motorized and non-motorized modes. We know that most non-motorized users really appreciate facilities that are separated from cars. But separate facilities—particularly those that are grade separated—requires space and money.

Boulder, Colorado has a strong tradition for coming up with the funding for these underpasses. In the city’s 25 square miles, they just finished constructing another adjacent to the University of Colorado Boulder Campus. The city has over 80 underpasses (I think) and this one is close to their most expensive. It came in at $7.4 million with $3.4 million in federal transportation funds. The local match for this project was composed of funding from five agencies.

As an owner of property less than 2 blocks away—and one who formerly crossed this intersection multiple times per day—I cannot help to be pleased. I no longer need to wait at the onerous light and have my child come anywhere close to the somewhat fast moving auto traffic on Broadway.


Bikesharing in Toronto

Having read and heard for years about bikesharing systems worldwide, I figured it was time to finally try it firsthand. I rented a BIXI while at the Conference of the International Association of Travel Behavior Research in Toronto.

The stations are convenient, though more are always welcome. The bikes are heavy (not surprising). It is liberating to use a vehicle for transport and not have to be concerned about what to do with when you are done.

Here are some other reactions, thoughts, and/or suggestions:

-Is there a systematic rationale for the location of the cargo rack? I see that most systems have the racks on the front; I assume this is because the riders want to have a constant eye on their belongings. However, when transporting heavier or larger cargo (e.g., a loaded backpack), this creates some instability when it comes to steering; furthermore, the size of the rack seems a bit limiting.

-It might be nice to equip the bikes with maps of return stations, particularly for those users without smart phones or knowledge of the locations for all the stations? I found myself circling several blocks trying to locate such.

-Downtown Toronto is far from a welcoming environment for cycling—an environment made even worse owing to the tracks from the streetcars. I am really surprised by the number of cyclists that do ride in the downtown area—a phenomena that is a combination of hearty Canadians and drivers who are largely respectful.

-As expected, the bikes are tanks. I guess they need to be but it kind of limits the overall fun on being on a bicycle.

-I understand that Montreal’s BIXI system is still reluctant to release their data. Interesting.

Copenhagen Bike Highways

I am in Toronto at the 13th Meeting of the International Association of Travel Behavior Research. The delegation is almost 250 people strong and extremely international. It is interesting to hear the tenor of planning and research efforts worldwide. It is always fun to hear the European’s impression of the transport-land use culture in North America.

In conversing with Danish colleagues, I relayed how the bicycling culture in the US has really taken off in the past few years. I queried the degree to which there is an analog in Denmark (i.e., while their cycling culture is very strong, have they also noticed more than a general uptick in use and attention). The answer is yes—even the Danes are enjoying considerable increased attention to cycling.

What is the current focus of their planning aims? More bicycle highways, as the type recently publicized in the NYTimes via text and video.

North American bikesharing (one word) report released

A new and very “up-to-date” report is out on bikesharing systems in North America, Susan Shaheen (of car sharing fame) was the PI.

The Mineta Transportation Institute ( has released a peer-reviewed research report, Public Bikesharing in North America: Early Operator and User Understanding. It documents the state of public bikesharing in the U.S. and Canada, including key factors such as essential attributes and business models; economics and insurance issues.

The best contribution of the report (other than being thorough, recent, and having many different forms of data–including surveys, interviews, etc.) is that they spend time looking at the funding and financing of these systems. Almost all of the systems receive sponsorship; most are non-profits. And, they are expensive. es; evolution of IT-based bikesharing; impact of bikesharing on walking, bicycling, public transit, and exercise; and other key factors. It also offers public policy recommendations. Principal investigator was Susan Shaheen, PhD, with Elliot Martin, PhD, Adam Cohen, and Rachel Finson. The free 138-page report is available for download at

Also, of the almost 30 systems that are reported in mainland North America prior to June 2012, it is stunning that none are west of Boulder (outside of Golden, BC)–the absence (for now) is particularly noticed in progressive hotbeds like Vancouver, Seattle, Portland, San Francisco (thought some of these places are still trying to figure out the helmet issue and others are planned).