Herbert Mohring


Herb Mohring

Lee Munnich passes on news that famed transportation economist, Herb Mohring, passed away on June 4. His biography in wikipedia is below:

Herbert Mohring: "Herbert Mohring was a transportation economist who taught at the University of Minnesota from 1961-1994. He received his Ph.D. from Massachusetts Institute of Technology in 1959.

He is widely known for his identification of what was dubbed the Mohring effect of increasing returns in public transportation (see: Mohring (1972) for details).

Mohring and Harwitz (1962) also showed that the revenues from the first-best congestion tax exactly cover the construction costs of highways when highways possess constant returns to scale.

Important Works

  • Mohring, Herbert, Optimization and Scale Economies in Urban Bus Transportation, American Economic Review 62, no. 4 (September 1972): 591-604.

  • Mohring, Herbert, The Peak Load Problem with Increasing Returns and Pricing Constraints, American Economic Review 60, no. 4 (September 1970): 693-705.

  • Mohring, H. and Harwitz, M., Highway Benefits: An Analytical Framework, Ch 2, pp 57–90. (1962)"

Much of his widely cited scholarly work can be accessed here.

A review of a paper extending Mohring's work: Cost recovery from congestion tolls with random capacity and demand and risk aversion by Robin Lindsey was given at the session in honor of Herb Mohring International Transport Economics Conference. June 16, 2009.

A policy presentation by Herb's friend David Lewis presented at the same session: America's Traffic Congestion Problem: Toward a Framework for Nationwide Reform.

Update 6/15/2012: Obituary published in Star Tribune.


I got to know Herb Mohring in the 1990s as he was ending his career with the University of Minnesota's Department of Economics but still conducting research with one of his PhD students on equity impacts of congestion pricing and how they could be addressed with the significant value created by reducing congestion through efficient pricing. Herb's early work on congestion pricing in the 1960s helped lay the theoretical groundwork for congestion pricing, and Herb inspired me to tackle the more practical political and institutional issues in implementing congestion pricing. No small fete as we all learned.

Herb and I traveled to Singapore for a conference on congestion pricing in 1994, where we saw the successful downtown congestion pricing scheme that had worked since 1974 and also observed early tests of the electronic road pricing (ERP) system that replaced their window tag system. Herb was an honored speaker at the conference that included transport economists from around the world.

Herb spoke at regional congestion pricing workshops we organized with the FHWA and MnDOT in the late 1990s. While Herb's economic lectures frequently went above the heads of the transportation practitioners who attended, it was always exciting to have a founding father of congestion pricing at these events. And of course, Herb was always charming and fun to be with when he wasn't talking economics.

At one of the regional workshops, Herb made the statement that he didn't expect to see congestion pricing implemented in the U.S. in his lifetime. I took this as a challenge and set out to do my part to bring congestion pricing to the U.S. during Herb Mohring's lifetime. While the MnPASS lanes on I-394 and I-35W are perhaps modest applications of congestion pricing, I feel I have done my part to respond to the "Mohring Challenge" and prove Herb wrong.

I was happy to work with David Levinson in organizing a tribute to Herb Mohring at the 2009 International Transport Economics Conference in Minneapolis. David Lewis, Robin Lindsey, and Erik Verhoef all spoke about Herb Mohring's contributions to transport economics. I am sad at the loss of my dear friend and colleague Herb Mohring.

By Herbert Mohring

Every adult American has had the unpleasant experience of being stuck in a traffic jam. Our
highways seem, at times, to be caught in a dreadful gridlock. Demand for new highways is
constantly growing and the search is on for ways of meeting this demand. While the
Minneapolis-St. Paul area is not yet as congested as, say Southern California, our traffic
problems do seem to be getting worse. What, if anything, can we or should we do about this
problem? A favorite of modern day urban planners is to provide alternative modes of
transportation such as buses or light rail systems. Such systems require very substantial subsidies
with fares typically accounting for less than a quarter of operating expenses. In spite of
substantial investments in alternative modes of transportation, public transportation use continues
to decline in the United States.

Congestion on roadways is an inevitable consequence of the way we charge travelers. In
choosing when and how to travel, every road user takes into account the delays they expect, but
nobody considers the delays they impose on others. It is entirely rational and sensible for each
user to ignore costs imposed on others. But these costs can be sizable. Think of a congested
highway in which cars are traveling bumper to bumper. If we add a car in the middle, we delay
all the cars behind that car by the time required for a single car to travel one car length. This is a
small cost for each delayed car but it is borne by every automobile that is delayed. In fact, we
can roughly estimate the costs imposed on others by adding a single automobile to a congested
roadway. This cost is the product of the number of automobiles behind the added automobile
and the time required to travel a single car length. Say we think of adding an automobile in the
middle of the pack. The time that that automobile takes to reach its destination is the is the
product of the number of cans ahead of it and the amount of time to travel one car length. So, the
cumulative delay imposed on others is exactly equal to the travel time of a typical automobile.

Each traveler takes into account the time required to travel for himself or herself but rationally
ignores the equal time cost imposed on others. The solution is to confront people with the true
costs of travel in congested time periods. Tolls are an obvious way of confronting people with
the time costs. With modern technology, it is possible to use transponders to make collection
easy. A possible way of solving the congestion problem is to buy tolls at peak times of travel on
specified lanes of highways or even the entire highway. It is important the tolls be higher for
peak times travel than for non-peak time travel in order to induce people to change their travel
times to do so. It might even make sense to, in the toll revenues, to subsidize non-peak time
travel! Alternatively, toll revenues could be used to subsidize buses or other forms of mass
transit. Such subsidies are preferable to our current use of sales and property tax revenues to
subsidize mass transit.

Congestion charges do invite heated (and often misinformed) debate. Sometimes they are
regarded as unfairly taxing people who simply need to travel at peak time. This criticism is not
particularly well-founded. The whole point of congestion charges is to make travel easier for
those who simply need to travel at peak times. So, much of the tolls paid by such individuals is
returned to them in the form of quicker and easier commutes.

Professor Herbert Mohring of the University of Minnesota has done much of the pioneering work
in figuring out how large tolls should be. His best estimate is that an optimal toll on Interstate
35W would be of the rate of 20 cents per mile or about $2.00 to $3.00 for travel from the
southern suburbs to Minneapolis. This is not a particularly onerous charge (it is less than the cost
of parking in much of Minneapolis) and would go a long way to solving our congestion problem.
(Some of his research can be found in a paper titled “Congestion” which appeared in pp. 181-
222 of Jose A Gomez-Ibanez, William B. Tye, and Clifford Winston, Essays in Transportation
Economics and Policy: A Handbook in Honor of John R. Meyer, Washington, DC: Brookings,

David Levinson

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This page contains a single entry by David Levinson published on June 6, 2012 8:42 AM.

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