Friday, October 31, 2008

New Bicycle Research

As this entry from the Center for Transportation Studies CTS Research E-News: October 2008 notes, Fay Cleaveland and I have completed our work on the relationship between new bicycle facilities and bicycle commute share. The abstract is below, and the full report can be found here

A 2005 study by Barnes, Thompson, and Krizek examined how the addition of bicycling facilities during the 1990s influenced localized bicycle commuting rates in the Twin Cities. They found that new facilities had a small but consistent and statistically significant impact on increased rates of bicycle commuting in areas immediately surrounding these facilities. This study expands on these findings by applying the same methodology to six other cities that experienced new facility construction during the 1990s. The purpose is to determine whether results from the Twin Cities are consistent elsewhere and to identify possible contextual factors influencing facilities' impact on bicycle commuting rates in a given city. We conclude that the "build it and they will come" theory is not universally applicable; context factors are an important element in determining the effectiveness of new commuting facilities. Among the key factors we identified were the level of publicity surrounding new facilities, the utility of routes to commuters, and the overall connectivity of the city's bicycling network. This evidence will aid in the evaluation of bicycle facility investment as a congestion reduction strategy.

Thursday, October 30, 2008

Car-sharing - now providing green power to the grid!

Well, the folks at HOURCAR have taken Carsharing to a whole new level.

Research, such as ours, has shown that carsharing can lead to more efficient travel choices. However, HOURCAR now is pushing that efficiency to the home, by running plug-in hybrid cars in its fleet that get their charge from photovoltaic solar panels. When the cars are not in use, they contribute power BACK to the grid.

The economic ramifications of this becoming the norm boggle my mind. We now have a prototype transportation technology system that not only will greatly reduce our need for gasonline - and the gas tax revenues that go with it, but also our reliance on the power grid. How will this loss of revenue impact transportation and power utilities as we know them? (well, congestion pricing could help!)

But, for the same reasons the environmental benefits are almost equally mind-boggling.

In the coming months, we'll be adding to this conversation with a new report on HOURCAR's impact on travel behavior and auto ownership in the Twin Cities, including presentation of the findings at the Transportation Research Board annual meeting in January!

Tuesday, October 28, 2008

Bicycle Awareness

It's been a while since I mentioned anything about bikes - and that seems to be putting me in the minority! Indeed, before the temperature and gas prices dropped, it seemed more and more people were getting on their bikes. Unfortunately, it also seemed that more were getting hurt or even killed, too.

Minneapolis Mayor recently commented on these trends, noting in an e-mail update that, in Minneapolis, "there’s been a downward trend in traffic crashes since the late 1990s including in the number of reported bike-vehicle accidents. From 1993 to 1999, the average number of bicycle crashes was 334 per year. Since 2000, the average has dropped 269 per year, a 20 percent decline."

The Mayor attributes this decline in crashes, and high rate of bicycling, in part, to increased facilities for bicycling.

He MIGHT be on to something. Research by Gary Barnes and Kevin Krizek found that there was a notable increase in bike rates on new facilities in Minneapolis in the 1990's. However, a forthcoming study Fay Cleaveland and I recently completed indicates that "if you build it, they will come" is not necessarily true.

While publication of the latter study is forthcoming, a couple events will be taking place here at the Humphrey Institute on this very topic (details below). Hope you can join us!

TODAY!, October 29, 2008, 12:30 to 1:30 pm, Associate Dean Greg Lindsey will give a talk in room 184 on "The Built Environment and Physical Activity: Models of Urban Trail Use." Professor Lindsey is Associate Dean of the Humphrey Institute and specializes in environmental planning, policy, and management at the state and local levels. His current projects involve analyses of activity patterns on urban greenways and the effects of greenways in urban communities.

Then, on Friday, November 14, in room 215 at 9:00, Bike Walk Twin Cities and U of M Department of Computer Science researchers Reid Priedhorsky and Loren Terveen for "How Cities and Regions Can Plan & Map
Together: A Geowiki Solution for Instantly Sharing Planning Information" This will be a demonstration of the first Twin Cities geowiki, called "cyclopath" (you can view cyclopath at View Cyclopath at Please RSVP by 11/7/2008 to David at

Play with visualization

Earlier this month, we hosted some very interesting presentations on the potential for visualization technologies to enhance public participation. The slides from that presentation are posted here here

Then, earlier this week, Planetizen showed how a different visualization technology could be applied to the Presidential campaign.

The technology driving the PlaNETizen post was Many Eyes, which shows how all sorts of data can be put into visual format. Check it out. My left brain and right brain have not gotten along so well for a long time!

Thursday, October 23, 2008

University Launches Rural Safety Partnership with Isanti County

Oberstar CERS panel.jpg
The Center for Excellence in Rural Safety (CERS) has launched a new local partnership with Isanti County to reduce traffic deaths and serious injuries. Congressman James Oberstar, who has been a key leader in efforts to improve safety in the area and also initiated CERS in the federal surface transportation law in 2005, was on hand for the launch. CERS Research Director Tom Horan, demonstrated Safe Road Maps/Minnesota, a new feature of the successful web mapping tool that has drawn enormous national interest.

The partnership is the first of its kind and represents a new approach to bringing the policy, technical and outreach expertise of the University of Minnesota to support state and local government in tackling high fatality rates in rural areas. Road fatalities remain high in the U.S. with over 42,000 deaths a year, with a disproportionate share, about twice the urban rate, occurring in rural areas. Isanti County has a Toward Zero Deaths (TZD) program that engages local leaders and institutions in developing and carrying out strategies to reduce road fatalities.

Dehn Oberstar Bollenbeck.jpgOf particular note is the work of Judge James Dehn, who has taken on the problem of driving under the influence of alcohol by working with bars to tackle the problem of DUIs with a Safe Cab program. The Safe Cab program is a collaboration of bar owners and managers, law enforcement, the local taxi company, sponsors and liquor businesses to provide free rides home or at significantly reduced cost for patrons at participating bars. The program is funded privately by the bars and liquor establishments, sponsors and donations. According to Judge James Dehn of the 10th District Court, the number of DUI cases, tracked in his courtroom from January 1, 2008 through July 30, 2008 is down by 42 percent compared to the same period in 2007.

See articles:
County joins national effort promoting safety on rural roads
County chosen as pilot site to promote safety
Safe Cab program demand up, DUI cases in Isanti County down

Monday, October 13, 2008

Should a mileage tax replace the gas tax?

Steve Berg recently posted an article on "Should a mileage tax replace the gas tax?" on following the Humphrey Institute's roundtable on the German model of distance-based transportation finance.

Berg captured a primary argument for the mileage-based tax: "A stagnant tax rate on gasoline isn't the only problem. As fuel prices rise, people drive less, buy less gas and pay less tax. The move to fuel-efficient cars, including hybrids, also lessens the revenue flow." At the same time, national studies have shown that we are significantly under-investing in transportation infrastructure in the U.S. A national commission shows the U.S. "spending about $225 billion a year on maintaining and building roads, transit, rail lines and other surface projects. Governments currently are spending about $90 billion. In other words, the country must find a way to increase its infrastructure investment by 2œ times in order to catch up."

Sunday, October 12, 2008

A Freeway Congestion Pricing Paradox

Patrick DeCorla-Souza, an expert on congestion pricing with the Federal Highway Administration (FHWA), explains how congestion pricing can actually increase the volume of traffic during peak periods as well as reduce congestion.

(with apologies to Chao Chen and Pravin Varaiya, who wrote an article with a similar title “The Freeway Congestion Paradox� in 2002)

A primary goal of congestion pricing of entire roadways (all lanes) is to reduce vehicle use during peak hours in order to reduce congestion. Congestion pricing of roadways into the central areas of London, Stockholm and Singapore has demonstrated the ability of pricing to reduce excessive traffic and thereby alleviate congestion.

Therefore, it is not difficult for transportation professionals to accept that congestion pricing of a freeway (all lanes) could have a similar effect – reducing both traffic volumes and congestion during peak hours. However, this discussion attempts to explain a seeming paradox – that congestion pricing, if well designed and combined with active traffic management, could actually increase traffic volumes served on a freeway during peak periods (in addition to person throughput).

Let’s consider a freeway with the following vehicular demand (i.e., vehicles arriving) at a bottleneck location during the morning peak period, expressed as vehicles per lane (vpl):

5am to 6 am 1400
6 am to 7 am 2200
7am to 8am 2400
8am to 9 am 2200 (plus 400 queued)
9 am to 10am 1400 (plus 600 queued)
Total 9600

With a low demand of 1400 vehicles per lane per hour, traffic flows freely from 5 to 6am, exceeding 60 mph. In the next hour, demand reaches the sustainable capacity of 2200 vehicles per lane per hour (based on TRB’s Highway Capacity Manual), and traffic flows more slowly averaging 45 to 50 mph. Demand reaches 2400 vehicles per lane over the next hour (7 to 8 am) causing the flow of traffic to break down and speeds to be erratic. With this breakdown in flow, throughput through the bottleneck drops to 2000 vehicles per lane per hour. (This is consistent with the approximately 10 percent drop in throughput observed at bottleneck locations when flow breaks down). Consequently a queue of 400 vehicles per lane (vpl) is formed at the bottleneck by the end of this hour. Demand during the next hour (8 to 9 am) drops to 2200 vehicles per lane. But since traffic flow is now in the breakdown condition, throughput is still 2000 vehicles per lane per hour. Therefore, at the end of this hour, the queue length increases from 400 vpl to 600 vpl. In the final hour of the morning peak period (9 to 10 am), demand drops to 1400 vpl. Thus, by the end of this hour, the 600 vpl queue is cleared, at the lowered throughput rate of 2000 vpl.

Now let us consider the same bottleneck with a well-designed congestion pricing strategy designed to maximize vehicle throughput by combining it with active traffic management, including ramp metering. Active traffic management and pricing complement one another, for the following reasons:
· Demand varies significantly from day to day for a variety of reasons. However, on a priced freeway, prices must be pre-scheduled (rather than set dynamically) since the entire freeway is being priced. Drivers will need to know the toll rates before they leave their origins, rather than on the trip, since they will not have a choice once they are on the freeway. Therefore, if pricing is deployed by itself, prices would have to be set high enough to keep demand much below the sustainable capacity level. If pricing is deployed with active traffic management, however, ramp metering could be used to hold excess demand at on-ramps if and when this may cause traffic flow to break down, and speed harmonization could be used to delay the breakdown of traffic flow.
· Ramp metering by itself has limited applicability for severely congested freeway systems, because queues at on-ramps can get too long and disrupt traffic flow on the surface street system. But since pricing encourages some drivers to travel at other times, on other modes or on other routes, the total number of vehicles queuing at on-ramps would be reduced, making it easier to deploy ramp metering effectively. (Note: Fairness issues relating to longer queues at ramp meters in inner cities are easily addressed – toll credits may be provided based on the amount of time spent in the queue).
· Speed harmonization, by itself, is capable of delaying the breakdown of traffic flow. But when combined with pricing, excessive demand can be curbed, thus potentially allowing speed harmonization to keep traffic flowing throughout the peak period.

Thus, active traffic management must be a key part of the overall freeway congestion pricing strategy, in order to prevent the breakdown of traffic flow and maximize vehicle throughput. Revenues from pricing may be used to pay for investment in active traffic management infrastructure and operations. Gantries used for lane control and speed harmonization may also be used to mount electronic toll readers and enforcement cameras. As a metropolitan area grows and travel demand increases, toll rates will increase to balance demand and supply, providing the extra revenue needed for additional investment in highway or transit capacity through the bottleneck. The overall strategy will create a “FAST� system that will be:
· Flexible enough to respond to varying levels of demand throughout the peak period
· Actively-managed to prevent breakdown of traffic flow and maximize safety
· Sustainable financially through the longer term future as a metro area grows
· Throughput-maximizing

Now let’s consider the same freeway discussed above, with the “FAST� approach. With graduated variable tolls between 6am and 9am, the FAST approach can keep traffic at the level of sustainable capacity, and may result in the following shifts in vehicular demand (i.e., arrivals) at a bottleneck location during the morning peak period, expressed as vehicles per lane (vpl):

5am to 6 am 1500 (increased by 100)
6 am to 7 am 2200 (same)
7am to 8am 2200 (reduced by 200)
8am to 9 am 2200 (same)
9 am to 10am 1500 (increased by 100)
Total 9600

In reality, some vehicles may shift to alternative toll-free routes to avoid the toll, while others who previously used the alternative toll-free routes may shift to the freeway to take advantage of the travel time savings and reliability of service. Traffic may increase by 100 vpl from 5 to 6am, since some travelers may shift to avoid the tolls beginning at 6am. In the next hour, demand is kept at the sustainable capacity of 2200 vehicles per lane per hour, because the 100 vpl demand that shifts to the earlier hour is replaced by 100 vpl shifting from the 7 to 8 am hour to get a lower toll rate. Demand is reduced to the sustainable capacity of 2200 vehicles per lane over the next hour (7 to 8 am) because 100 vpl shift to the earlier 6 to 7 am hour and another 100 vpl shift to the later 8 to 9am hour to get a lower toll rate. Demand during the next hour (8 to 9 am) stays at 2200 vehicles per lane (the sustainable capacity), because the 100 vpl that shift from the earlier hour to this hour are balanced by 100 vpl that shift from this hour to the 9 to 10am hour to avoid paying tolls. Consequently, the total demand in the 9 to 10am hour increases to 1500 vpl.

The reader will note that total vehicle “throughput� as presented above for the 5-hour morning peak period is 9600 vpl for each case. This assumes that there will be no mode shifts and no route shifts. I acknowledge that these are not realistic assumptions. Depending on the nature of the corridor and available transit and ridesharing options, one could expect a further reduction in vehicular demand of 100 to 1000 vpl over the 5- hour period, which would be replaced by “new� vehicles that are either diverted from some other route or time of travel, or are completely new “induced� trips. Person throughput in the corridor may thus be expected to increase.

The big question is – what will happen in the 9 to 10 am hour, during which travel is toll-free and which carries only 1500 vpl vs. 2000 vpl in the base case without pricing. Will the spare capacity, available toll-free, result in new trips or from trips being diverted from some other route or time of travel? Since the 9 to 10 am hour was congested and in breakdown flow condition in the base case, one can assume that alternative toll-free routes would be at least as congested during that hour. If these toll-free routes still remain congested (since they are not priced), could we expect some travelers from these alternative routes to shift to our priced bottleneck route to take advantage of the toll-free service in the 9 to 10am hour?

If you believe that some drivers will divert to the freeway, you will now see the paradox: Congestion Pricing Can Reduce Vehicular Travel Demand While At the Same Time Increasing Vehicle Throughput Through the Freeway Bottleneck

A paper describing other ways in which congestion pricing and active traffic management work together is available at:

Patrick DeCorla-Souza, AICP,
Federal Highway Administration,
Washington, DC,
Phone: 202-366-4076;

Wednesday, October 8, 2008

Technology for planners: going beyond maps and post-its

Inspired by the enthusiasm of Yingling Fan we recently hosted Dr. Ted Grossardt from the University of Kentucky Transportation Center. His expertise is in Structured Public Involvement, which is a protocol for using technology to greatly enhance the quality of public involvement processes in planning. In his presentation, he discussed how he and his colleagues have achieved useful feedback through enhanced modeling techniques (using fuzzy modeling) and computer-aided visualization technologies. More information on his work is included below.

In addition, he has graciously agreed to share his presentation slides here

A fundamental problem of most public infrastructure planning and design projects is how to usefully and efficiently engage the public in the appropriate aspects of the process. Well-meaning but lengthy meeting processes exclude citizens with limited time budgets, while rapid, short processes limit the quality and quantity of overall public input and reduce its usefulness to professionals. In both cases, as well, various subsets of the public can legitimately claim process injustices and challenge planning and design outcomes. As the questions become more complex, the challenges to effective public involvement multiply, and professionals are caught in a choice among bad solutions.

Structured Public Involvement is a protocol that combines the use of innovative dialogic techniques, technological tools for representation and feedback, and quantitative tools for capturing and modeling public responses. CommunityViz® is used as the visualization tool to help residents better understand the differences between potential land development patterns, an audience response system was used to gather their preferences in real time, and Fuzzy Knowledge Builder® was used post process to model the complex interplay of development pattern properties that were most preferred and least preferred by citizens. The development patterns vary by percent mixture of housing types, percent mixture of land use types, percent given over to green space, the ratio of sidewalk to total paved area, and the connectivity of the road network. These five parameters were chosen as the most useful and fundamental measures of differences between development patterns, and citizens’ preferences were derived based on them. Public input for this town was successfully gathered and modeled and the resulting preference patterns made available to city planners for use in updating their comprehensive plan.

This protocol is notable in that it exhibits high process transparency and public satisfaction with the process.

Relevant References:

Bailey, K, Grossardt, T. and Pride-Wells, M. 2007. Community Design of a Light Rail Transit-Oriented District using CAVE (Casewise Visual Evaluation). Socio Economic Planning Sciences 41(3): 235-254

Nelessen, A. 1994. Visions for a New American Dream: Process, Principles and an Ordinance to Plan and Design Small Communities. American Planning Association Press, Chicago and Washington D.C.

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