Dr. Mark McDonald: Postmortem Analysis of the Let’s Move Nashville Plan’s Train Wreck

by Dr. Mark McDonald, Professor of the Practice of Civil Engineering at Lipscomb University


There is no doubt after the transit referendum that the proposed master plan was found to be a train wreck by almost two of three voters. This is a most unfortunate situation, as the window of time to manage Nashville’s rapid growth is shrinking and if not managed competently, Nashville will pay dearly for it. In this article I will provide my insight as to why the plan failed, what I think is good and bad about the result, and where I believe Nashville should go from here.

Let’s first of all establish a few baseline facts. Nashville’s surface streets in the urban core are approaching gridlock at peak hours. Nashville’s interstates are operating regularly at level of service F at peak times, when most of our citizens need the network to be reliable and efficient. Our primary arterials are operating at capacity, and we will have a very large number of people moving to middle Tennessee in the next 20 years. Our city’s infrastructure is totally unprepared to handle this population explosion, and to make matters worse, the additional motorists expected on our highways will require traffic to slow further for drivers to maintain safe spacing. The arrival rate will go up at bottlenecks, the service rate will go down at bottlenecks, and the transportation system will fail to serve its needed function in the coming years. Any analysis of traffic data found on Google Maps easily confirms the truth that Nashville is facing a serious transportation crisis in the coming years.

This impending crisis will be fueled by a network of major problems. First, 80 to 100 people will be moving to Nashville every day, with a wide distribution of income. Second, these people must find a place to live in a housing market where demand far exceeds supply. Third, the places in middle Tennessee with homes that are affordable are often outside of Davidson County. Fourth, many will work in Nashville but will not be able to afford to live near their place of employment and must commute. Fifth, Nashville has a hub and spoke structure to its transportation network, and people often find themselves choosing housing options as close to the interstates as possible, placing them far away from the urban core. Sixth, families with children often choose to live outside the reach of Metro Nashville Public Schools. These dynamics are creating sprawl that is out of control and a perfect storm for Nashville’s transportation system.

Nashville is not alone in facing rapid urban growth. Cities worldwide have been dealing with these problems, and the very best strategy for dealing with rapid urbanization is to place infrastructure and development in socially desirable locations before people show up. Of course, doing so requires careful attention to issues in equity, as gentrification disrupts neighborhoods and often leaves the economically disadvantaged most vulnerable to being forced out of their neighborhoods.

So why would a comprehensive transit plan that will provide sorely needed capacity fall flat at the ballot box? A number of poor decisions were made that turned the plan for light rail into a train wreck. Let’s list at least a few of them.

1. The public lost trust in Megan Barry, and for good reason. This plan was synonymous with the Mayor and many likely saw the transit referendum as a chance to express public outrage over her egregious actions. I think that this created the Achilles Heel that made life easy for the no tax side. This one issue alone ran the plan off the rails.

2. Light rail and the tunnel were too expensive for most Nashvillians to swallow. While Nashvillians would have still had an overall tax burden far less than the vast majority of Americans even if the plan passed, many moved to Nashville because of its low tax rates. Regardless of the need or merit, most Nashvillians thought of these as too expensive.

3. More attention should have been paid to autonomous vehicle (AV) technology. Autonomous vehicles have the capacity to do great things. They will solve problems of access and egress, but they will not likely shift the balance of traffic demand. It is highly questionable whether the public, who is addicted to their cars, would be willing to adopt the AV mode of transit. If people don’t give up use of their personal vehicles then AV’s solve absolutely nothing. People are addicted to independence and trip chaining. People prefer not to sit in taxi cabs the whole city sits in. There will be much more public resistance to adoption of AV’s.

However, AV’s will likely be an essential part of a successful total transportation system, and should be integrated in the overall scheme of operations.

4. More use of dedicated infrastructure BRT should have been made. While AV’s are likely to become an essential part of the transit plan, and the right fleet composition of AV’s will help improve operations, BRT can be quickly implemented. BRT should have dedicated lanes, as it will not be competitive without the dedicated infrastructure. However, certain types of AV’s can possibly become part of the flow in BRT lanes (especially MTA operates AV’s), and in time, the vehicles used in the express lane will have higher degrees of automation regardless of size and capacity.

5. Marketing for the plan was incompetent. The pro transit side did not make the case to the public of why transit creates enormous external benefits and why those traveling by their personal vehicle benefit from a transit system. When a few drivers switch modes on roadways operating near capacity, every other user still driving their own vehicle have significant reductions in travel time. As such transit systems need not pay for themselves at the farebox. Their existence is justified on the basis of the external benefits they provide society.

6. Nashvillians are unhappy with the consequences of not having to pay the social costs of their own travel activities, but refuse to pay even part of the social costs of their travel activities, either in the form of paying for additional infrastructure capacity or in congestion pricing (which is currently legislatively impractical).

7. Dark money. This was a factor on both sides. While Andy Martin of No Tax 4 Tracks believes that the dark money on his side was justified because it saved the taxpayers money, I feel that the dark money on the other side was equally justified on the merits of increased capacity of the system which would have provided sorely needed capacity and travel time reliability.

While I wish dark money was not a part of this referendum I do think it hurt the pro transit side more as the potential for conflicts of interest was far greater on the pro transit side.

8. A poor choice of election date. The referendum date in all likelihood drew those who wereunhappy with the plan at an over represented rate. The general election would have likely seen a larger turnout and a tighter margin.

So what’s bad about the results? First of all, there is no capacity to be added to the network in the near future. Second, Nashville is losing control over its growth and has less ability to make smarter growth happen. Third of all, time is wasted when decisive action is needed to control sprawl.

But is there a silver lining? I should say so. Nashville largely rejected light rail and a tunnel, but other cheaper and effective measures can be implemented much sooner than 2032. The big question is what the measures to implement. In my opinion, they should be:

1. Building neighborhood transit centers. These centers facilitate the transition of the bus network from a hub and spoke system to a system with greater connectivity as well as providing comfortable and safe spaces for transfers.

2. Increasing the number of cross town routes. Travelers should not have to transfer at Music City Central to make a trip on the same side of town on a different street. The lack of tangential lines and the requirement to transfer at the central hub also makes the bus infeasible for many trips.

3. Expansion of bus service, especially on heavily traveled corridors. In many parts of Davidson County, bus service is so infrequent that the bus is not a viable mode of transportation. To get more people to choose socially responsible modes of travel, the mode must be a viable one. This is axiomatic.

4. Development of dedicated BRT lanes in key corridors, especially the corridors where light rail was proposed. This is likely to run into resistance from the no tax side, because it will likely require a good deal of money to implement. However, the expense will be nowhere near the amount that would be required with light rail). The driving public will likely complain that precious road space is given to transit. However, the public must also realize that in less than 20 years their driving habits will be unsustainable with current infrastructure. A tipping point is coming where traveling in a single occupancy vehicle is so difficult that it would be better to use BRT. At that point a BRT and perhaps a combined BRT and high occupancy autonomous vehicle lane will be needed to manage the overflow and provide reasonable and reliable travel times.

5. Paying close attention to the infrastructure needs of AV’s and meeting them to the greatest extent possible, and choosing implementation policies that encourage travelers to make socially responsible decisions.

6. Make every effort to densify residences and provide mixed land use along important corridors.

Nashville can solve this impending crisis. It will require a less ambitious transit master plan that integrates sensible concepts for access and egress with cost effective measures to increase passenger throughput on its busiest corridors. It must be poised to take advantage of AV’s when they become commonplace. Nashville must have the will to make developers develop socially responsible housing along important mobility corridors to prevent sprawl.

It isn’t going to be free. It will cost money. It will require people to modify their behavior and use modes of transportation they haven’t used before. Fortunately, past experience shows that people are flexible if they have options. When a portion of the upper deck of the San Francisco Bay Bridge collapsed in the Loma Prieta Earthquake of 1989, the BART tunnel under the San Francisco Bay was fortunately left undamaged. The BART trains ran very full as people switched modes under extreme conditions. As travelers find congestion to be increasingly painful, many will eventually switch modes to transit if it is a reasonable alternative in Nashville.

Any realistic solution won’t fix all congestion problems, but the pain of traffic congestion should be used to steer users toward a transit option with enough capacity to handle the overflow demand. But the costs of not expanding the capacity of our transportation system will, in a few years time, be enormous, and I believe that Nashvillians will come to see that a major capacity upgrade is absolutely necessary.

I sincerely hope the realization doesn’t come too late.

– – –

Dr. Mark McDonald is a Professor of the Practice of Civil Engineering at Lipscomb University where he has taught a wide array of courses in Civil Engineering, including Transportation Engineering, Structural Engineering, Civil Engineering Materials, Engineering Economy, and Senior Design. He holds the Bachelor of Civil Engineering (2003, Summa Cum Laude and University Honors Scholar) from Auburn University, the MSCE (2004) from the University of California at Berkeley, and the Ph.D. (2008) in Civil Engineering from Vanderbilt University, where he served three years as an Assistant Professor before choosing to focus his career on engineering education. Dr. McDonald is a former Dwight D. Eisenhower Transportation Fellow and a former NSF IGERT Fellow in Reliability and Risk Engineering. He has published over 40 peer reviewed research papers in structural reliability, pavements and materials, transportation systems analysis, and the optimization of Civil Engineering systems.










Related posts

8 Thoughts to “Dr. Mark McDonald: Postmortem Analysis of the Let’s Move Nashville Plan’s Train Wreck”

  1. 83ragtop50

    Good try, but past experiences in other rapidly growing cities have proven that government is unable to provide a solution to the unbridled and outrageous growth rate that the tax hungry politicians promote. Just let nature take its course by allowing the pain of commuting initiate alternatives such as (1) telecommuting; (2) the development of satellite business centers and (3) the actual decline of the number of people moving to Nashville. What has worked to some degree in a few cities is the double-decking of major freeways (such as I-25 and I-65) with the upper deck being allocated for through traffic. The only thing I see in the article that has proven successful elsewhere is the increase in express bus service from outlining communities service by “park and ride” parking lots. I figure the next thing we taxpayers will hear (again) is that a toll road authority with taxing powers is needed to expand the number of roadways without raising taxes excessively. Public be aware that this is nothing more than a wolf in sheep’s clothing. Taxpayers pay for the construction of toll roads with bonds, then pay a typically outrageous tolls to use them then pay for never ending maintenance. Oh, and the construction of “free” highways will greatly diminish to force commuters to use the toll roads. Only the good ole boy highway contractors win in that scenario.

    1. Mark McDonald

      I am in agreement that the double decker concept will be a very important part of solving the problems Nashville faces. Part of the purpose of an interstate is queue storage, and that is provided with a double decker interstate system.

      As for your argument about sprawl, experience with almost every other major urban center in the years following public school integration shows that enabling urban sprawl wreaked havoc on transportation systems and exacerbated the problems. A significant number of home based work trips will be made to the central business district, and there is no way around it. Refusal to keep sprawl in check will wreak havoc on Davidson County.

      The largest complaint I have with the alternative ideas presented by the no tax side is that they do not take mode choice behaviors of individual users into consideration. High occupancy AV’s could well fail to attract a large enough mode share to even remotely make a dent in the problem.

      In my article I also mention the importance of mixed land use. It will be crucial to keep people from having to use the transportation system in the first place, but even demand side management won’t be adequate. Certainly not in 20 years when most corridors are at or over capacity operations.

      One thing is for certain. While the people of Nashville may reject public expenditures to provide solutions to the traffic problems the city faces, is certain that the people of Nashville will suffer the natural consequences of failure to act to manage the impending problems. If Nashville continues to make its bed, it will continue to have to lie in it.

      1. 83ragtop50

        Mr. McDonald, Thank you for a thoughtful response. I have lived through unsupportable growth elsewhere. Roads become clogged, garbage service is strained beyond the breaking point, etc. The politicians keep raising taxes with little impact despite the skyrocketing tax base. I continue to see AV’s promoted without consideration of the fact that this technology is still in its infancy. Everyone is ignoring the fact that AV’s are not failsafe and could even be hacked and controlled by those would cause innocent people harm. Naysayers would disagree but all one has to do is look at the attacks on the internet. The computers on some current regular production cars have already been hacked just to prove that it can be done. If it has a computer it can be hacked.

        Mixed use is fine for those who care to live in the environment. But I personally do not consider it a desirable environment. after having been exposed to it on various occasions. “Affordable” housing is a pipe dream with the explosive growth of Nashville. Forcing property owners who rent or desire to sell to do so to keep or increase “affordable” housing is at best coercion and at worst a form of socialism.

        1. Mark McDonald

          AV’s have some significant hurdles to be overcome before they should be thought of as a feasible solution. They aren’t likely to be the panacea the No Tax side made them out to be. AV’s will be a tough sell to a driving addicted population, as evidenced by the unwillingness of drivers to form carpools with people they know when the HOV lane offers them significant time savings. We currently have violation rates of upwards of 85 percent in our current HOV lane corridors. AV’s also have major issues related to pedestrian safety as well as ethical dilemmas related to decision making when facing almost certain crashes. In other words, if any maneuver the AV takes will present the choice of killing a schoolchild, a surgeon, a single mother of four, or number of people on an MTA bus, what should we program a vehicle to do?

          While I generally prefer market solutions to most social problems, transportation systems don’t typically do well under a laissez-faire approach. Often a transportation authority can institute controls that result in better equilibrium flows than drivers left to their own devices would experience. One well known case is the Braess Paradox, where the closure of links in a network can actually improve travel times for all users in the network.

          Another such paradox is Smith’s Paradox. This paradox is best illustrated by considering green time splits at a major and minor street in a network. Suppose minor street demand pressure increases relative to the major street. Optimal signal control principles indicate that green time should be allocated such that the volume to capacity rates are equal on all approaches. However, giving more time to the minor street will encourage more use of the minor street as users adjust. This would further incentivize users to take the minor street.

          The moral of the story is that in either case the transportation authority needs to design the system to encourage users to do what is best for the system overall, and the benefit of a few should not happen at the expense of the many.

          The same inference could be drawn with respect to BRT and/or high occupancy AV lanes. That lane will have enormous capacity because of the type of vehicle that uses it. Users may prefer to take their own vehicle, but Smith’s paradox warns that we should not cater to the automobile demand, especially when the links are under capacity. If the system can become easily accessed by paratransit, then it becomes a viable “link” in a transportation “supernetwork”. It is then the right thing to do to reward those using the BRT system with faster travel times and to protect the link from use by general traffic. Is this likely to be popular? Probably not. Will it be effective? Absolutely.

          With regard to development along the corridors, the city has the power to enforce zoning. This is because the government can resolve many disputes that arise from competing land uses. This may seem socialistic, but keep in mind that in America, our government is of the people, by the people, and for the people. If the people are upset with the decisions of government, then those in power are voted out of power. In a socialistic government, that isn’t the case.

          Many transportation problems are problems people cannot solve themselves because often the equilibrium that results is a highly undesirable one and the outcome that can result when external forces are applied can be far superior. Yes, that sounds socialistic, but in America it isn’t a socialistic position as our government is and should be accountable to the governed.

          1. 83ragtop50

            I have read in multiple places that studies show that the introduction of HOV lanes actually decreases the volume of traffic because of the reduction in the number of lanes allocated to the typically more heavily used “regular” lanes. Do you have any statistics to support the advantage of HOV lanes?

            Regarding zoning – the problem with correcting poor decisions made by those in power (who always believe they know best) is that the damage is done before they can be thrown out. I would much prefer local jurisdictions such as home owners associations and deed restrictions by developers to the overreaching of a central zoning body. Then the covenants actually are by the people directly affected.

          2. Mark McDonald

            HOV lanes are highly variable in terms of their result, some being highly successful and others total failures. A lot of the result depends on the level of enforcement as well as the willingness of the public to actually form carpools. Also, left lane exits can be very helpful to incentivize usage. Nashville has been highly reluctant to form carpools and to respect HOV lane restrictions, and law enforcement is not eager to enforce HOV violations as it is a fairly dangerous and difficult duty.

            Of course it will appear that traffic is reduced if the number of mixed flow lanes are reduced, but that would result from operations occurring at a lower speed and therefore a lower rate of flow at a denser point on the fundamental diagram. In other words, it would be like a fast food restaurant where a cashier goes on break right when eight buses of hungry high school band members, cheerleaders, and football players show up after a football game. The arrival rate will be very high but the service rate not nearly as fast. As for statistics, I can tell you that in a typical day at peak hour, some HOV lanes are nearly empty as long as the GP lanes are relatively freely flowing, but under heavy congestion the operations closely mirror operations in the GP lanes, but often at a slightly higher speed. It’s highly variable across and from spot to spot on I-65, I-40, and I-24. However, it should be noted that HOV lanes need only half the flow of a MF lane to achieve the same throughput of passengers as a GP lane.

            Nashville will ultimately reach a tipping point, and when it does, the pain will ultimately force individuals to adjust in multiple ways.

            With regard to zoning, citizens left unchecked can also do great damage. Good city planning places the infrastructure to support a city’s growth in places that allow the growth in ways that minimize problems and create maximal opportunities, and places it before the growth happens.

            Politicians can also do great damage. That’s why it is important to elect competent and transparent individuals and hold them accountable after election, and not only at election time.

  2. Steve L.

    And I believe that tax money spent needs to be well spent looking at the future. The solution to this problem is not to spend huge sums of money to improve travel routes into the city. Rather the solution should be to create metro business development centers at the edges of the city allowing citizens to stay away from those areas of congestion. The equivalent of “Shopping Malls” for commercial/banking/legal businesses. Ask folks why they are traveling into the city (what jobs they have and conducting what kind of business) and then provide those services away from the center of the city. Be innovative. Create new community centers that are easier on the environment and attractive to new residents.

    1. Mark McDonald


      What you are suggesting is going to be necessitated by traffic conditions. However, a transportation system that provides an unacceptable level of service is not acceptable. It’s a big problem with a need for a lot of strategies to solve it.

      Some strategies should be demand side, some should be supply side, and some of them should be technology driven. But it is highly unlikely that focusing exclusively on only one of these three will provide a good result.