Squeezing More Capacity from Existing Roads and Highways

focus4by James A. Bacon

Thanks to tax increases enacted in 2102, Virginia has roughly $800 million more to spend each year on transportation projects. But that money won’t stretch very far if we use it all to build more lane-miles of roads and highways. An alternative approach is to invest in making our existing assets operate more efficiently. “The Innovative DOT,” a handbook for stretching public transportation dollars in an era of government austerity, provides a half dozen strategies for doing so.

The Virginia Department of Transportation is pursuing some of these ideas, especially the use of technology to eke extra capacity from overloaded interstates, but the state’s newly appointed Secretary of Transportation, Aubrey Layne, would be well advised to review them all to see which might be pursued more aggressively. Key ideas from the chapter, “Transportation System Efficiency,” include:

Reform Level of Service.  A rigid focus on Level of Service (LoS), a measure of roadway congestion, can lead to overbuilding. Transportation departments typically base their LoS rating on the period of peak travel delay, which may be bad for only one or two hours per day, or on specific roadway segments not typical of the entire corridor. DoTs should consider payback — how much congestion relief is achieved per dollar spent? Also, they should broaden their focus beyond vehicle capacity, to include walking, biking and mass transit. Finally, they need to consider context. Some places are congested for a reason — they are centers of economic activity. Increasing the volume and speed of traffic sometimes can make those places less desirable.

Context Sensitive Solutions. DoTs often design projects to the highest specifications in the highway design manual, which can make them unnecessarily expensive to build and maintain. Worse, over-engineered roads can lead to increased volume and speed of traffic where it is totally inappropriate, such as commercial districts that need a pedestrian-friendly infrastructure to prosper. It would be helpful here to make Chuck Marohn’s distinction between streets (designed for local access by cars, pedestrians, buses and bikes) and roads (designed for high-speed travel between distant points). Often DoT “improvements” create what he calls “stroads,” or street-road hybrids which perform neither function well.

Street connectivity. Roughly half of all trips made in the United States are three miles or shorter; 28% are one mile or less. But the prevailing development pattern since World War II has been to build disconnected subdivision pods or shopping-center pods off major corridors. Because of non-existent connectivity between adjacent pods, drivers funnel onto already-overcrowded connector roads and arterials even to make short trips. As a condition for accepting subdivision streets into the public road system, local governments should consider requiring minimal standards of connectivity with other developments. “The Innovative DOT” specifically notes connectivity reforms in Virginia implemented during the Kaine administration and partially reversed during the McDonnell years.

Access management. DoTs allow their roads — including, here in Virgninia, state highways — to fall into ruin by failing to limit access by neighboring property owners. As the manual observes, “A road can become a victim of its own desirability, as an ever-increasing number of private driveways and entrances to commercial establishments dot the highway. The increasing number of turning movements and vehicles entering a high-speed roadway leads to increases in crashes and congestion and premature calls for adding travel lanes to reduce traffic patterns.” The pattern in Virginia, epitomized by U.S. 29 north of Charlottesville but a problem everywhere, has been to add travel lanes and, then, when that option gets too expensive, to build bypasses. The solution, suggests the manual, is to establish an access management plan for a corridor that sets standards for accessing the road. Virginia has established such a plan to prevent the further ruination of U.S. 29, but I am not certain how well it is enforced.

Transportation Demand Management. Transportation Demand Management (TDM) attempts to alleviate congestion by focusing on the demand side of the equation, reducing demand for scarce roadway capacity by urging people to walk, bike, telecommute, carpool, van pool, ride mass transit and adopt flexible work hours. These efforts can be complemented through dynamic road pricing for roads, parking and transit, which raise the cost for driving solo during hours of peak demand. As it happens, Virginians need look no farther than Arlington County to see one of the nation’s most sophisticated TDM programs at work.

System management. System management solutions encompass an array of technology-oriented solutions to increase roadway capacity, such as traffic light synchronization, signage that alerts motorists to traffic conditions, rapid incident response to clear traffic accidents and ramp meters that control the rate at which vehicles enter a highway during periods of peak demand. This is an area where Virginia excels. The state has five state-of-the-art traffic management centers, it has installed traffic signage on all major highways, and it is investing heavily in technology upgrades to Interstate 66.

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8 responses to “Squeezing More Capacity from Existing Roads and Highways”

  1. TDM, transportation demand management, can be incredibly effective in reducing the “need” for additional highway capacity, greenhouse emissions, congestion while increasing public health and decreasing the need to subsidize transit.

    In Perth, Australia and it’s suburbs which has had an “aggressive-passive” TDM program, called TravelSmart, since 1997, annually — the state government reports, they are decreasing VKT (like Vehicle Miles Traveled, except with Kilometers) 13 percent, increasing transit boardings 4.4 million, and adding 7 million hours of physical fitness while saving citizens some $25 million ANNUALLY. Each year, the area of 1.6 million people produce 88 million fewer tons of carbon dioxide in driving some 30 million fewer kilometers.

    Unlike virtually — and perhaps ALL — American TDM, Perth focuses on getting people to try alternative transportation for any trip, not JUST the commute trip. Once people feel comfortable with biking,, walking, transit or carpooling for less crucial trips they gradually become willing to try that all-important work trip WHILE becoming advocates for alternative transportation. Siince they also usually discover personal money — and surprisingly time — savings, they provide transportation researchers with rich understanding of how/why people get from here to there in any transportation mode.

    1. That’s fine for Perth, AU… but a completely different built environment than anywhere in Virginia. Walking or biking to most employment in NoVa would be kind of suicidal, no?

  2. Thought this was interesting:

    If VDOT is allowing localities to maintain their own secondary roads does this include any engineering/design control? Also wondering if Arlington’s TDM needed to be vetted by the state, or was it just something they did on their own.

  3. There are different flavors of devolution that include maintenance only – using VDOT or not to design, construction and operation (like traffic signals) – but it has to be done to VDOT standards – which are def facto national engineering standards – AASHTO.

    you can see the county standards for Va here:


    also… national and state roads that go through counties remain the responsibility of VDOT which employ things like access management and TDM,

    on the subdivision connectivity – that would (I think) end up being the county preference if they took over their own secondary and subdivision roads with the state still determining access standards if the subdivision and secondary streets connect to a National (US signed) or State (Primary signed) road.

    but VDOT’s job is to preserve and protect the functional utility of the roads – to move traffic. They do not decide land-use but they have to deal with the consequences of land-use and they are more and more asserting themselves on these issues.

    The VDOT folks who maintain and operate the roads are a very different group that those that plan new roads… they work quite differently in fact.

    On the LOS – JimB nailed it. LOS and it’s cousin V/C (volume capacity ratio) are instantaneous measures not broader measures.

    for instance, you can have two roads rated LOS F and one of them experiences LOS F – upside-down V/C (a ratio greater than 1 – i.e. volume greater than capacity..congestion) – one experience that condition 30 minutes a day and another for 2 hours a day.

    but both roads can end up being characterized as LOS F.

    a good example would be a road with a side entrance from a school or a big plant… normally – it’s LOS B or C but a “peak” hour, the road “fails” at LOS F… “fail” not meaning permanent deadlock but rather a temporary condition often seen as having to wait for multiple light changes to get through the light.

    the other thing – at peak hour – regionally – just “fixing” one road does not help the other roads. If you have LOS F conditions over a wide area – like you would at peak hour.. fixing any one part of it does not “fix” the regional peak hour congestion. In fact fixing one part and making it flow better might just move that traffic to the next bottleneck – faster.

    I’m a critic of VDOT especially on new/proposed roads but I’m also an admirer/proponent of VDOT in terms of the maintenance/operations division. I think they do a pretty good job of maintaining and operating the roads… overall.. compared to other State DOTs, they tend to be among the leaders in efficiency and asset management.

    1. billsblots Avatar

      “The VDOT folks who maintain and operate the roads are a very different group that those that plan new roads… they work quite differently in fact. I’m also an admirer/proponent of VDOT in terms of the maintenance/operations division.”

      Indeed it’s as if they come from two different worlds, they are different cultures.

  4. The Tysons landowners and Fairfax County have made what I believe to be a very good decision on TDM. Virtually every commercial landowner in Tysons has a TDM obligation of sorts. This includes both properties rezoned under the new plan or under the old 94 plan. Through the efforts of Tytran and the Tysons Partnership, the landowners worked with the County and will generally consolidate their TDM operations through Tytran on a unified basis.

    So, instead of operating say 50 distinct TDM efforts, Tysons will operate a unified TDM plan. Resources can be pooled to achieve more efficient and effective solutions. While Tysons will continue to be a traffic monster (and a bigger one to boot), it should have a very good TDM program.

  5. billsblots Avatar

    Slightly related, more so to an article I commented on a few days ago, ( https://www.baconsrebellion.com/2014/01/coming-up-cars-and-traffic-lights-that-communicate.html ) the National Highway Safety Transportation Administration (NHSTA) has officially endorsed the Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) concept in a news conference yesterday. This has been a huge and lengthy international process between governments and auto manufacturers for more than 14 years. I commented on the potential fly in the ointment in the form of expansion of next-gen wi-fi into the frequency spectrum dedicated to V2V communications and its potential devastating effects on the whole system.

    FCC Chairman Tom Wheeler recently told Congressman Dingell (D-MI) “… the FCC would not allow additional WiFi if it interfered with the intelligent transportation systems (ITS) Dingell (and Michigan automakers) are concerned about.”

    As well as immediate alerts of collision-avoidance nature, this would provide real time traffic information that can be used for smarter traffic signal systems, incrementally increasing the volume of traffic that can move smoothly.


    1. I too have been following the latest news on talking cars… especially since billsblots had touched on it earlier and I’d be appreciative if you educate me a little more about the conflict between WiFI and talking cars… truly….

      is there really a potential problem.. say on a road near commercial businesses that have WiFi … and “bleed over” to cars?

      The other thing I noticed .. had overlooked.. was the fact that these connected cars are going to be not only broadcasting but broadcasting – potentially a lot of data – about each car…. perhaps specific to each car… which I’m wondering if people are going to be any more comfortable with that they might be with a “broadcasting” GPS unit…

      I see this as a potential sleeper issue with the public who might see/hear “connected cars” in the news but not immediately recognize the potential privacy impacts.

      what say you billsblots?

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