Surface Transportation Innovations Newsletter

Surface Transportation Innovations # 40

Topics include: a new solution for HOV occupancy enforcement; edgeless cities; arterial underpasses; intermittent bus lanes in Lisbon; more on the trucks-tolls debate; and other news.

In this issue:

A New Approach to Enforcing HOV Occupancy

The dirty little secret of many HOV lane programs is how poorly enforced the occupancy requirement is. We’ve all had the experience of driving alongside an HOV lane and seeing what appear to be single-occupant vehicles driving along as if they were entitled to be there. Counting heads is an iffy proposition for highway patrols, especially with heavily tinted glass, small children who may not be visible, or people in back seats.

This problem becomes far more acute when HOV lanes are converted to HOT lanes. Every vehicle in the lane illegally represents both a loss of toll revenue and a reduction in demand-management capability via the variable-pricing regime. As HOT lanes become more common, we’re going to need more-robust enforcement mechanisms than highway patrol officers attempting to count heads.

So I commend to you a report that recently crossed my desk. It’s part of a larger report on the expansion of the I-15 managed lanes in San Diego, prepared for SANDAG by HNTB, with the inelegant title of “Task 2.2.2, Enforcement Concepts and Technologies Report.” ( Its purpose was to “identify technologies and methods that could be used in the development of advanced vehicle occupancy detection” for the I-15 managed lanes (which are being expanded from two lanes to four, and from eight miles to 20 miles).

Unlike many planned HOT lanes, the current I-15 project has enough space to offer an “enforcement zone” partway along its length, at which head counts can more easily be made. But space constraints (and multiple ingress and egress points) will not permit that luxury on the expanded project. And even with the current enforcement zone plus “special enforcement” by patrol cars, the violation rates “have recently been closer to 15 percent of total average daily traffic” in the managed lanes-which is unacceptably high.

So the report systematically reviews a variety of actual and proposed technologies, including mobile enforcement transponders (as used on the I-394 HOT lanes in Minneapolis), infrared occupancy detection (being tested in Scotland), the use of smart-cards inserted into an on-board unit, and even in-vehicle occupancy sensors. None of these technologies can eliminate manual enforcement, and some suffer from serious cost and/or privacy problems.

Where the report makes a breakthrough is in suggesting a change in methods and procedures. One key idea is to require all managed-lane users to have transponders, whether HOV or paying. This could be combined with a requirement that HOV users be pre-registered, with their license plates entered into a database of authorized users. (This is starting to be done in Florida and Texas to enable non-transponder users to pay their tolls via license-plate billing-so-called video tolling.) But the report still calls for backup, manual enforcement.

Let me take this one step further. Recall that the original idea of HOV lanes was to reward those who reduced the number of peak-period vehicles by carpooling. So as part of the shift from HOV to HOT, we could refocus the carpools-go-free aspect on commuter trip reduction by allowing only employer-sponsored carpools to use HOT lanes at no charge (or a reduced rate). The local ride-sharing agency could issue transponders to participating employers, who would issue them only to carpool groups which they (the employers) certified as legitimate, regular carpools. Those transponder ID numbers would be identified in the billing/enforcement software as authorized free or discount users.

Hence, on-road enforcement would be entirely electronic: there is either a valid transponder or there isn’t, and in the latter case, there is a toll violation. The ride-share agency would need to periodically audit participating employers to be sure the authorized carpools were still active. Whenever a carpool was found to be defunct, the employer would retrieve the transponder, and the tolling software would delete that ID number from the authorized carpool list.

Given that some studies have found that between one-third and two-thirds of all current carpools are actually fam-pools, and that many HOV lanes also have violation rates between 10 and 20%, this redefinition of carpools would dramatically reduce the number of vehicles using the HOT lane without paying. So not only would enforcement costs drop significantly, but net toll revenue would also increase.

I have long argued that vanpools and buses (super-high-occupancy vehicles) should be the only vehicles authorized to use HOT lanes at no charge. But in places where the carpool aspect is considered very important, refocusing the HOV privilege on employer-sponsored carpools would be a major step toward more cost-effective transportation.

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Edgeless Cities and Rail Transit

Much of the debate about urban land use and mass transit is driven by misconceptions. All too many elected officials (and a declining fraction of transportation planners) still have the mental model of the mono-centric city-a single huge downtown where the majority of jobs are, able to be served effectively by radial transit lines from the suburbs. Think New York and Chicago-or more accurately Manhattan and the Loop.

One of the first popular challenges to this mono-centric view was Joel Garreau’s 1991 book Edge City, which identified the growing phenomenon of large-scale office and retail developments in the suburbs. More recently, Robert Lang of Virginia Tech provided a more sophisticated look with his 2003 book Edgeless Cities. Lang found that a large and growing fraction of commercial development actually exists in smaller and more scattered forms across the whole urbanized area. And that pattern, of course, makes transit (and especially rail transit) a far more difficult proposition.

Lang and two colleagues recently published (via the National Center for Real Estate Research) a further analysis, which I commend to your attention. “Beyond Edgeless Cities: Office Geography in the New Metropolis” presents the results of analyzing 13 large urban office markets, using a geographical information system (GIS). They describe what they call the new suburban metropolis, which is urban in function but not in form. “Many suburbs now have essentially all the elements that make a place urban,” but arrayed in a form that differs considerably from the mono-centric model. The new metropolis “is mostly low-to-mid density, automobile dependent, and dispersed.”

The new analysis finds that edgeless cities account for almost 40% of the total office space in those areas, while their downtowns averaged 33% and their edge cities just 14%. The balance fell into “urban envelopes” (5.2%), “corridors” (3.8%), and “secondary downtowns” (1.2%). You can download the report at

The most fascinating aspect of the report is not the averages but the differences among these large urban areas. Atlanta and Miami have the smallest fraction of office space downtown, at just 6.7% and 8.7% respectively. The edge-city champions are Houston (33.3% edge-city space), Detroit (27.1%), and Washington, DC (23.3%). And the metro areas with the largest fraction of their office space in edgeless cities are Miami (72.1%), Detroit (54.1%), Philadelphia (54.3%), and Denver (50.8%).

The final sections of the report discuss policy implications. Citing a 1977 study by Pushkarev and Zupan which found that 8,000 people per square mile was the minimum threshold for rail transit, Lang and colleagues parsed their data to determine the amount of edgeless city office space located in neighborhoods with at least that much density. Atlanta had zero, and another seven had only single-digit percentages. The most promising were Los Angeles (36.7%), San Francisco (27.8%), and Miami (13.8%). Those portions of those metro areas were suggested as feasible candidates for rail transit-and all three of them do have various rail projects in being and others under way.

Note: the Boris Pushkarev and Jeffrey Zupan book is Public Transportation and Land Use Policy: Indiana University Press, 1977.

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Underpasses at Arterial Intersections

A lot of research on congestion focuses on urban freeways. But arterials (multi-lane divided roadways) carry a sizeable amount of urban traffic, and are also subject to serious congestion. Traffic signal synchronization in the peak direction can help, but has its own limitations. It has the advantage of being relatively cheap, but provides significant improvements in flow only on arterials with strongly directional flow-you can’t have rolling greens simultaneously in opposite directions.

One approach that has not gotten enough attention is grade separation at intersections-creating an underpass to let through traffic on one arterial pass beneath the other one. That’s more versatile than signal synchronization, since it provides continuous flow in both directions on the route using the underpass. But with limited budgets, city and state DOTs have been reluctant to use this approach.

That’s why a 2003 paper by Gregory Dehnert and Panos Prevedouros of the University of Hawaii is worth knowing about. They analyzed a lower-cost version of the idea: the low clearance underpass. Instead of building it to provide the standard 16-foot clearance height, they proposed just eight feet. That permits all current cars, SUVs, and vans to use it, with a one-foot margin of safety. Trucks and buses (10% of the total, in their study) would have to use surface-level through lanes.

The costs of the low-clearance underpass would be lower, because of less excavation and material, a shorter length (39% less, with the same 5% grade), and less need for additional right of way acquisition. Using data from the Hawaii DOT, they estimated the construction cost to be 38% less-not counting any savings from reduced right of way.

Selecting a congested arterial in Honolulu, they modeled the addition of four such underpasses, using a traffic simulation model of the whole roadway network. They found a 7% reduction in AM travel time in the corridor, and a 16% reduction during the PM peak. When they estimated the value of the time savings over the course of a year, they estimate that the underpasses would pay for themselves over a two to five year period.

Taking a closer look at their assumptions in this calculation, I find it to be very, very conservative. Personal travel time is valued at just $7.80/hour, truck traffic at $19/hour, and savings were counted for only 250 days/year and for only two peak hours per day. With more realistic assumptions, the break-even period would be even less than the 2-5 years they estimated.

Note: This paper was published in ITE Journal, Vol. 74, pp. 36-47, March 2004. If you are not an ITE member, you can get a copy from Prevedouros:

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How About Intermittent Bus Lanes?

Bus Rapid Transit is a very promising approach to better transit service at low cost. In Los Angeles, the Metro Rapid service introduced on congested Wilshire Blvd. proved so successful that it’s been expanded to 16 other arterials. Transit planners are justifiably proud, but would really love to be able to run the service on exclusive bus lanes, instead of in regular mixed-flow lanes. Trouble is, taking away a whole lane each way on crowded arterials like Wilshire and Ventura Boulevards would add hugely to congestion, while wasting much of the bus lane capacity.

That’s why I was intrigued with a presentation at last month’s Transportation Research Board annual meeting by Jose Viegas of the Instituto Superior Tecnico in Lisbon, Portugal. The title of the presentation (which is on the TRB annual meeting CD-ROM) is “The Intermittent Bus Lane System: Demonstration in Lisbon.”

Viegas introduced the concept of an intermittent bus lane (IBL) 10 years ago, and his paper reports on the first demonstration project, in Lisbon, which he and his colleagues designed. The basic idea is that the lane functions as a regular traffic lane when a bus is not present. As a bus approaches a section of the lane (a block or two), the lane’s status changes and usage is limited to bus-only. Obviously, making this work depends on technology for monitoring bus locations in real-time and for alerting drivers (via lane-lighting and variable message signs) about the changing lane status.

The demonstration project took place on a half-mile avenue near the main university area in Lisbon, at the edge of the central business district. It ran for six months, beginning in September 2005. During peak hours, bus speeds were 45-60% higher than without the IBL, with a daily average speed increase of 15-25%. Surveys of motorists showed good acceptance; the IBL was perceived as fair sharing of limited roadway space. Viegas told us they are about to launch a second demonstration, in a more complex location, this time including photo enforcement.

Assuming that further demonstrations show additional positive results, Viegas will have introduced an important new tool for the transit tool box. IBL is not the answer for all bus routes; an arterial like LA’s Wilshire Blvd. may have too much bus service to make it practical there. But for many cities and many arterials with 5 to 10 buses per hour, the IBL looks like a way to provide many of the benefits of an exclusive bus lane without the huge negative impacts on traffic of totally removing that lane from general service.

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Trucks and Tolling: the Drama Continues

On the same day (Feb. 9th) that Govs. Rendell of Pennsylvania and Daniels of Indiana spoke eloquently about the transportation benefits from leasing their respective toll roads at a White House transportation summit for state legislators, a trucking industry coalition held a DC news conference to denounce toll road leasing. They charged that such moves burden taxpayers and could have negative impacts on safety, security and motorists. The American Trucking Associations statement even called for the goal of a toll-free national highway system. Ten days later I faced off, briefly, with ATA president Bill Graves on this subject, on CNBC.

It’s unfortunate that things have come to this pass, because there is much to be gained by truckers and shippers from increased use of toll finance and public-private partnerships. As I’ve been pointing out recently at conferences, the current fuel tax/trust fund model is terrible at targeting new-capacity investment to projects that will yield the highest rate of return. Instead of replacing the freight-critical Gerald Desmond Bridge serving the Port of Long Beach, the feds fund a Bridge to Nowhere in Alaska. The system systematically shifts funds from high-growth states like California, Texas, and Florida to low-growth states. It’s no wonder the rate of return on highway investment has declined to the low single digits in recent years.

Fortunately, other thinkers are starting to make the tolls/goods-movement connection. Both Transportation Secretary Mary Peters and Undersecretary Jeff Shane have talked up the potential of toll truck lanes. At a Jan. 24th hearing before the House Transportation & Infrastructure Committee, Shane pointed out that freight transportation is projected to grow even faster than passenger transportation, and we face a severe capacity crunch, based on business as usual funding mechanisms. Transportation consultant Alan Pisarski suggested that “There may be rewards in finally separating cars from trucks in major corridors.” And when it comes to paying for them, “We should be happy to build the roads the truckers need, and they should be happy to pay for them.”

Some interesting work along these lines is being carried out by the American Road & Transportation Builders Association under the name Critical Commerce Corridors. It’s conceived as a 25-year plan to develop additional goods-movement infrastructure capacity in key corridors, with dedicated user-fee funding. ARTBA is talking with other major groups that have a stake in keeping our logistics system running smoothly, such as the National Association of Manufacturers, National Industrial Transportation league, and the National Retail Federation.

The trucking groups don’t seem to realize that the leasing of a few high-profile toll roads is just a small part of a much larger and more important phenomenon: the infusion of global capital into a capital-starved U.S. highway system. The multi-billion-dollar new toll road projects that keep being announced in Texas are a foretaste of what we can look forward to if we create a comparably friendly investment climate in other states.

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News Notes

Limitations of Hydrogen BMW. Like many of you, I’d love to see the widespread use of emission-free motor vehicles. So I was intrigued by BMW’s announcement last fall of a hydrogen-powered luxury sedan. Then I read the fine print. First, the H2 fuel tank weighs 369 pounds and takes up half the space in the trunk. And because the liquefied H2 slowly turns into a gas, a half-full tank will completely boil off in nine days. Because the car can only go 125 miles on its hydrogen fuel supply, it also has a gasoline engine and gas tank, good for another 300 miles. Clearly, this project is not ready for prime time. (Source: MIT’s Technology Review, January/February 2007)

Governors Support Funding Options. An excellent new issue brief from the National Governor’s Association, released earlier this month, summarizes “State Policy Options for Funding Transportation.” It gives a good overview of the shortcomings of the status quo, and then reviews a series of options: tax-based, toll and pricing options, debt financing, and asset leases, among others. Yes, asset leases, as in “lease the Pennsylvania Turnpike.” No populist demagoguery here-just hard-headed practical advice. The Indiana Toll Road case is presented as a brief case study. Go to:

Correction re Earmarks. In Issue No. 39, I drew upon a Wall Street Journal front-page story on congressional earmarks in transportation funding laws, using its example of the proposed wildlife bridge across a Colorado highway. Proponents of the bridge sent me a news release noting that the funding for this particular project comes from the Public Lands Highway Discretionary Program, and that this money does not reallocate funds that Colorado DOT would otherwise spend on higher-priority projects. I’m happy to set the record straight.

Poll Shows Strong Congestion Concern. A Harris Poll released Feb. 22, 2007 found that 37% of U.S. adults say that traffic congestion is a serious problem in their community. And of two-thirds of that 37% say it is not being addressed-which they are probably right. Reason’s Mobility Project last year found that nearly all the urban area long-term transportation plans we reviewed did not focus on reducing traffic congestion as a major goal, and that most of those that included a projection of year-2030 congestion showed it as being significantly higher than current levels. It’s good to see that people are increasingly catching on that not much is being done about the problem. One remedy most people do not support, however, is London-type congestion pricing. In response to the poll’s questi on (which called it a congestion tax), 66% were opposed, most of them strongly. Only 22% said they would support it.

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