As part of an interesting FIVE part series focusing on different considerations in the paths that people take for travel (i.e., why is it not always the shortest?), the Transportationist discusses our bicycle route choice experiment.
In 1991 the City of Münster (Germany) aimed to raise support for the city’s spending on bicycling infrastructure. The press office of the city made a poster comprised of three panels. Each panel’s background displayed Münster’s Prinzipalmarkt, the cobblestoned main street in town; what differed in each panel was what filled the Prinzipalmarkt. The first depicted what the street looked like if 72 people were transported by car; the second, by bus; the third by bike. The main point was that bicycling is an extremely efficient way to use limited transport space in cities.
Twenty years later, Indian-based organization, Earthian, posted the figure to Facebook. It quickly went viral. The graphic has since been used prominently in presentations worldwide to advance the arguments that bicycling is a strategic means of transport; bicycling can help reduce traffic congestion. In theory, it makes sense. And, the “reduced congestion” argument is one of the more prevalent ones in the advocate’s arsenal. It carries water for places with exceptionally high cycling use or for specific corridors. The argument, however, is fatally flawed when applied to larger units of geography.
The source of the substitution
The implicit assumption in the reduced congestion argument is that there is a substitution effect between a cycling trip and a vehicle trip. If true, it is helpful to consider the source of the substitution and its magnitude. For example, using mode share figures based on the US, a starting point suggests bicycling would draw from other modes in proportion to their current mode shares. Bicyclists would therefore draw roughly 85 percent of their market from driving trips (solo or with others), 10 percent from walking trips, and the remaining from transit or other. If most converters would come from existing transit users, a reasonably safe assumption but a population whose travel comprises a meager two percent of travel (again, in the US), then these numbers are relatively small. Tapping into the mindset of converting auto users presents a greater challenge.
The magnitude of the substitution
Understanding the magnitude of the substitution effect is difficult mainly because it is based on a counterfactual condition (e.g., if Booth would not have killed Lincoln, then…). There are two ways to think about it. One can start with a fixed number of vehicle trips and assume a share of those trips that are replaced by bicycling. Alternatively, one can consider the number of bicycle trips and estimate the share of these trips that replace driving. The two analysis strategies are not comparable.
Our own work found a wide range using the later approach, ranging between 25 and 68 percent of bike trips claiming to substitute for car trips. This suggests that half of the existing bike trips, were they not by bicycle, would be by car. Such rates of substitution, I presume, vary wildly across the globe. Then think about places where cycling comprises more than half of all trips: Groningen (the Netherlands), Münster (Germany) or Copenhagen (Denmark). It is hard to conceive of the character of these iconic bike-friendly cities if most trips were by car. Most bike trips substitute and the congestion savings is remarkable. But outside of these select settings, it is hard to know. In the rest of the world, if the logic is applied to a particular corridor, the congestion savings argument might have a noticeable impact.
Vehicular travel is not fixed
For most cities, there is a there is an inherent fatal flaw with the foundations of the above logic. These flaws become apparent when congestion is considered on a larger scale or for places that are growing (the birth rates in the above mentioned towns are not exactly skyrocketing). The foundation assumes a fixed demand for travel, and vehicular travel in particular. Prevailing trends of population growth and auto ownership suggest otherwise. Coupled with what is generally known about travel behavior, and driver behavior more specifically, these factors paint a meager picture for cycling’s ability to address congestion.
Traffic congestion is a problem is that is both old and complex. Rome struggled with it, resulting in Caesar simply issuing a ban on carts and chariots back in the day. Things aren’t that easy in most cities and more recent thinking has focused on its source and solutions. A good portion of that thinking is framed around issues of capacity: building more roads or widening existing roads and what is referred to as the effects of induced demand. Any form of relief provided for drivers, the story goes, will quickly be gobbled up. Drivers will defect to the corridor where the relief is offered. Other drivers, previously sleeping in and starting their commute at 9:30 will join the 8:00 am rage. Still others who were previously carpooling or using transit, learning that their route is as bad as it used to be, will switch to driving. Add traffic from the inevitable new development down the street and any immediate gains become a wash.
A key outcome from most of this thinking has been coined the “Iron Law of Congestion,” suggesting that once congestion has reared its ugly head in a city, there is little the city can do get rid of it. Congestion is largely an inescapable condition in all large and growing metropolitan areas across the world.
The same logic applies to gains from getting more people on bikes; it might provide temporary respite which would be gobbled. Suppose a community cycling initiative can leverage the previously explained phenomena to the fullest. Transit users and car users alike convert to bike travel for most trips. Getting more people on bikes might mean less people driving cars; it might mean temporary relief in the previously congested corridor. But using the Iron Law and considered across the region, the effects on congestion would be futile.
Congestion is less about capacity
But that’s not all. Driver behavior is also a culprit to congestion. Tom Vanderbilt’s book, Traffic, climbed its way to become a top ten best seller on the New York Times list in August 2008. It is the only book focused on transport that has claimed such a coveted spot. One of Vanderbilt’s principle claims is that traffic congestion has more to do with driver behavior than capacity issues. Drivers switch lanes, rubberneck, merge too early or overcompensate when braking—all relatively small flaws in driving behavior—but in the aggregate, they have a major impact on congestion.
Such driver errors and their consequences on congestion will diminish over time; automated vehicles will likely clean up such mishaps. However, this stream of thought suggests congestion has less to do with overall capacity in general. Even further evidence of the importance of the operations of a system in terms of congestion comes from New York City’ recent experience. Over the past years, the city has been aggressively reallocating select street space for cyclists and pedestrians, thereby decreasing overall vehicular capacity. Analyzing taxi cab logs, however, the Bloomberg administration contends that travel speeds have remained steady despite such decreased real estate—an outcome that is largely attributed to improvements to the city’s traffic signal system.
Cycling’s limits to reduce congestion is perhaps best understood when the argument is taken to an extreme. Scaling up to large and quickly growing cities, the latent demand ready to consume any relief to existing congestion is overpowering. Projections from the United Nations paint a picture of adding more than one million people to the earth every five days for the next dozen years. Admittedly, the majority of this growth will be absorbed in cities of developing countries and its impact being unequally distributed and perhaps even barely felt in Europe. But with rising incomes generally across the globe, the more than 60 million cars that are produced each year (more than 100 new cars every minute) will likely find willing drivers. The primary drivers to congestion (pun intended) are more powerful than anything that bicycling can realistically impact over the next decade or two, globally speaking.
There might be good reasons to spur bicycling and build more facilities to do it. The congestion relief might be felt locally. Aiming to reduce congestion on a regional level, however, is one of the least reliable rationales for doing so. Cyclists are better off making hay from other, more reliable arguments.
 Transport econometricians refer to this as the principle of Independence from Irrelevant Alternatives (IIA)
 Summary of Travel Trends: 2009 National Household Travel Survey, http://nhts.ornl.gov/2009/pub/stt.pdf
 Piatkowski, Dan, Kevin J. Krizek, and Susan Handy (2013). Accounting for the Short Term Substitution Effects of Walking and Cycling in Sustainable Transportation. Working paper available from the Active Communities / Transport (ACT) Research Group.
 Most of the original research is attributed to David Lewis [(1977), Estimating the influence of public policy on road traffic levels in greater London. J. Transport Econ. Policy, 11, pp. 155–168] and Martin Mogridge [(1990),Travel in towns: jam yesterday, jam today and jam tomorrow? Macmillan Press, London].
 Anthony Downs is largely credited with popularizing some of predominant thinking, starting with his 1992 book, Stuck in Traffic: Coping with Peak-Hour Traffic Congestion (1992), The Brookings Institution: Washington, DC. The concept is better explained in his updated work a decade later, Still Stuck in Traffic (2004), The Brookings Institution: Washington D.C.
 See, for example, http://www.nytimes.com/2013/09/05/nyregion/in-bloombergs-city-of-bike-lanes-data-show-cabs-gain-a-little-speed.html or other reports such as the “Green Light for Midtown Evaluation” (January 2010), from: http://www.nyc.gov/html/dot/downloads/pdf/broadway_report_final2010_web.pdf
 Population Division, United Nations, Department of Economic and Social Affairs. World Population Prospects: The 2012 Revision.
 Figures provided by the International Organization of Motor Vehicle Manufacturers, see: http://www.oica.net/wp-content/uploads/2013/09/total-production-2013.pdf
This past weekend I visited the “the Eternal City,” Roma, Italy. The Romans thought that no matter what happened to the world, no matter how many other empires might rise and fall, their city would be everlasting. Most cities have ups and downs; their transportation corridors, usually, are another story; most have eternal lives. Once a transportation corridor is cemented (pun partially intended), it has a staying power rivaled by few inventions or fabrications in the world. Some of original paths worn by the Etruscans outside my apartment in Bologna today continue to serve as main conduits of economic activity for the region. Gravity has determined the outcome of most original Roman structures, but their roads are also still widespread throughout parts of Europe, Africa and Asia. Even the canals in northern Europe, built by the Roman empire for irrigation, later helped the British pioneer the industrial revolution; these canals y are still carrying barges, albeit leisure ones. The transportation function along any corridors rarely exists in its original form. Technologies change. Types of economic activities change. Fashions change. This largely explains why you don’t see many donkeys filling the streets in Israel anymore. Outside of the nostalgic horse and carriage for tourists and weddings in Paris, there are not many of them on the streets either. The streetcars employed in hundreds of cities across the US have been torn up for car only use.
The transportation future of cities will continue to be surface-based, with cars and existing roads playing prominent roles. But over time, the nature and character of select corridors change to better serve the needs and demands for other modes. More overall space will be made available for bikes—a contentious topic but one whose writing is largely on the wall. A sticking point is where to find the space for this change, a proposition that will require altering the nature of many transportation corridors in cities.
With urban areas built up, cities largely have four options before them to find more space. They can: (a) extend in another dimension, aerially or subterranean, (b) find new right-of-way space, (c) widen existing right-of-way space. These first three options are either technologically difficult, involve displacing people (rarely a good idea) or are prohibitively expensive.
A fourth option requires cities to reconfigure existing space by altering the use patterns along it. Changing the nature of the transportation services along a corridor. In most cases, this option involves scaling back car use in one way or another. This is analogous to taking candy away from a child (taking space away from cars). And, its trouble points are primarily political (not financial or logistical as identified in the prior solutions).
Many corridors in urban areas already have initiatives that are rethinking the role that the car has played in the past half-century. These initiatives range from charging for or banning car use during certain times, reducing capacity by removing a travel lane, reducing capacity by reducing speed (via narrower travel lanes), removing on-street parking or all together, turning a street over to other modes. These are all steps in the same direction. Cycling’s ability to realize these gains rests in its ability to better leverage these types of initiatives by downsizing existing facilities and gently expanding alternative networks. But not all roads. Just select ones.
Where is the low hanging fruit and what criteria can help cities reinvent corridors for cycling?
- Communities first need to identify stretches of road that have “proven” themselves from a cycling perspective. These places might connect key origin-destination pairs. They might be currently serving cyclists who are experiencing hardship conditions. Then there are two synergistic interventions.
- The second step is scaling back car use. Addressing the fact that high vehicular speeds are the largest culprit to unfriendly bike environments is key. Harnessing cars to speeds below 40 km/h is necessary. If a community accompany such speed limits with reductions in the widths of vehicular travel lanes–or even the removal of some of them—all the better. (Pushing such a proposal through the political process likely involves a gentle nod to address how alternative corridors might be able to better absorb some mild enhancements to vehicular capacity via intersection design, signal timing, or on-street parking modifications.)
- Building up cycling facilities. Designated cycling corridors, at a minimum, deserve on-street delineation of cycling routes. This might start with a marked lane, a buffered lane (with paint), a raised path, or even physical barriers from adjacent traffic. Furthermore, intersection treatments go a long way.
Transportation corridors have amazing staying power. Cities can and should work with their existing bones to further cycling; they don’t necessarily need to search endlessly for new corridors. But there is nothing to suggest that the existing roads cannot be downsized for car use or more generally, have their purpose altered along select routes.
Some of the most robust research, internationally, of the health benefits derived from switching car use to other modes is coming out of the Centre for Research in Environmental Epidemiology (CREAL) in Barcelona. They have looked at the impacts of Barcelona’s bike-sharing system in the past. Their latest work is more generally about the benefits of public transport and bike. Yes, they are working with future scenarios. Yes, there are lots of assumptions embedded. But the framework and the identification of key outcomes and specific measures is good to see.
Replacing car trips by increasing bike and public transport in the
greater Barcelona metropolitan area: A health impact assessment study
Volume 49, 15 November 2012, Pages 100–109
Rojas et al.
Estimate the health risks and benefits of mode shifts from car to cycling and public transport in the metropolitan area of Barcelona,Spain.
We conducted a health impact assessment (HIA), creating 8 different scenarios on the replacement of short and long car trips, by public transport or/and bike. The primary outcome measure was all-cause
mortality and change in life expectancy related to two different assessments: A) the exposure of travellers to physical activity, air pollution to particulate matter < 2.5 μm (PM2.5), and road traffic fatality; and B) the exposure of general population to PM2.5, modelling by Barcelona Air-Dispersion Model. The secondary outcome was a change in emissions of carbon dioxide.
The annual health impact of a shift of 40% of the car trips, starting and ending in Barcelona City, to cycling (n = 141,690) would be for the travellers who shift modes 1.15 additional deaths from air pollution, 0.17 additional deaths from road traffic fatality and 67.46 deaths avoided from physical activity resulting in a total of 66.12 deaths avoided. Fewer deaths would be avoided annually if half of the replaced trips were shifted to public transport (43.76 deaths). The annual health impact in the Barcelona City general population (n = 1,630,494) of the 40% reduction in car trips would be 10.03 deaths avoided due to the reduction of 0.64% in exposure to PM2.5. The deaths (including travellers and general population) avoided in Barcelona City therefore would be 76.15 annually. Further health benefits would
be obtained with a shift of 40% of the car trips from the Greater Barcelona Metropolitan which either start or end in Barcelona City to public transport (40.15 deaths avoided) or public transport and
cycling (98.50 deaths avoided).The carbon dioxide reduction for shifting from car to other modes of transport (bike and public transport) in Barcelona metropolitan area was estimated to be 203,251
t/CO2 emissions per year.
Interventions to reduce car use and increase cycling and the use of public transport in metropolitan areas, like Barcelona, can produce health benefits for travellers and for the general population of the
city. Also these interventions help to reduce green house gas emissions.
- We assess the health impacts of replacing car trips by bicycle or public transport.
- Replacement of the car trips reduces mortality in travellers who shift the mode.
- Replacement of the car trips also reduces mortality in residents of urban areas.
- Replacement of car trips can reduce the emissions of CO2.
Until someone can convince me that we have more consistently administered and robust measures of cycling walking–at least for comparative purposes and for the entire US–we continue to rely on the ACS.
Based on the summary from Wendell Cox, from ’10 til ’11, bicycling and walking each increased 0.03. Bicycling is now at 0.56%; walking is at 2.82%.
Most communities around the US celebrate bike to work day and week in May. The idea is to celebrate and promote the whole concept and get more people on-board. In Colorado, the Front Range communities wait until the 4th Wednesday in June. It is quite a celebration with the Regional Council (DRCOG) playing an active role. There are over 45 breakfast stations in city of Boulder alone–that’s almost 2 stations per square mile of town.
The whole idea, it seems, is to get people to “register” for the event and thereby “pledge” to do more of it–almost 1,800 of them across the Front Range. I’m not sure I fully follow the wisdom of such, but it seems harmless. Relative to previous years, it seemed that attendance was a bit down in Boulder, likely owing to the obsessive heat for several consecutive days prior and the onset of pretty dramatic forest fires.
The ACT Research Group will be partnering with DRCOG analyzing some of the survey results. Some positive university press has already been generated. Our central research question is going to focus on those who do it this day but not the rest of the day–drilling down into the strength and duration of the “lag effect” of such an intervention. Supposedly 30% were first time participants.
One of the best scenes from the movie, “It’s a Wonderful Life” is when George is flirting with Mary after the dance:
(Mary Hatch Bailey): I’ll take it! Then what?
(George): Well, then you can swallow it, and it’ll all dissolve see, and the moonbeams would shoot out of your fingers and your toes and the ends of your hair… am I talking too much?
(George): You want me to kiss her, huh?
(Man on Porch): Ah, youth is wasted on the wrong people!
(Clarence): One man’s life touches so many others, when he’s not there it leaves an awfully big hole.
A new report released by the CoPIRG Foundation demonstrates that Coloradans and Americans have been driving less since the middle of last decade. The report, Transportation and the New Generation: Why Young People are Driving Less and What it Means for Transportation Policy, shows that young people in particular are decreasing the amount they drive and increasing their use of transportation alternatives