Time to Overhaul Traffic Engineering Guidelines

focus5by James A. Bacon

Employees of the Virginia Department of Transportation, like most transportation departments, see themselves as being in the profession of building roads for cars. The challenge is to move the highest volume of cars as rapidly as possible through a given number of lanes. Designing roads for the convenience of pedestrians, bikers and transit riders is typically an after-thought. Let someone else worry about sidewalks and bus stops.

VDOT could accomplish great good if it tweaked its mission. Instead of focusing primarily designing streets and roads for cars, it should design roads and streets for everyone. In a word, it should design Complete Streets.

That slight change of mission could accomplish wonders to improve mobility and access in Virginia. That’s not to say it will be easy. A streets-for-everyone approach would require adopting different design guidelines detailing lane widths, curb radii, intersection design, pedestrian crossings, on-street parking and a whole lot more. Perhaps even harder, it would require a change in culture and outlook: acknowledging that in some locations, it may be necessary to sacrifice automobile volume and speed to accommodate other modes, knowing that the payoff is fewer cars on the road.

Smart Growth America’s “The Innovative DOT” manual makes the case that fiscally strapped state transportation departments can stretch their dollars by approaching old problems in new ways. The chapter, “Improving Options for Mobility and Access,” discusses how to promote Complete Streets, mass transit and bicycle-pedestrian travel as an alternative to the automobile.

The first step, I would argue, is to understand the distinction between “roads” and “streets,” as delineated by Strong Town’s Charles Marohn. Roads provide mobility, primarily for vehicles, over long distances — between cities and towns, across metropolitan areas. These should be designed for maximum speed and traffic flow. The problem, the manual explains, is that traffic engineers have tended to apply the same kind of thinking to streets, where the emphasis is on access. Streets are where people get our of their cars to work, shop, dine out, conduct business… and, if they live nearby, even to walk home. Blurring the distinction creates street-road hybrids, or stroads, that fail to fulfill either function well.

When traffic engineers apply “road” standards to “streets,” they tend to do some unfortunate things. They create wider lanes so cars can drive faster. But wider lanes eliminates space that could be dedicated to bicycles, bus stops and on-street parking; they also create greater distances for pedestrians to cross when they walk across the street. Engineers tend to blunt their street corners with larger curb radii so cars can take corners at higher speeds. That makes intersections even wider for pedestrians. And faster car speeds scares non-cars off the streets. DOTs should adopt “context sensitive solutions” that apply guidelines that are appropriate to the urban context.

Designing Complete Streets is only part of what’s needed. In preserving the distinction between roads and streets, DOTs also should be more aggressive about access management — curtailing access to state highways, for instance, by subdivisions, shopping centers and other property owners along the road. Highways should be highways, not main streets, as they have become in every metropolitan area across Virginia. Appreciating the different functions of roads and streets and applying appropriate design standards to each could go a long way to creating more livable communities and solving our transportation problems.

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8 responses to “Time to Overhaul Traffic Engineering Guidelines

  1. There’s a bit of a problem with their narrative especially in Va where every city and town controls most it’s streets – not VDOT, except for the US signed and State signed roads.

    Even then there are issues.

    Take US29 in Charlottesville – get rid of the proposed bypass and then look at the original US 29 and try to think of it in terms of ped/bike friendly.

    The subtle question is – WHO does US-29 through Charlottesville “belong” to – Charottesville or the State/VDOT?

    What was/is the original purpose of US 29?

    was it built and designed as a city street or a US road to move traffic to other parts of Virginia?

    but leave that aside for the moment – and look at the other streets in Charlottesville – and ask yourself who they “belong” to and who has responsibility for the arterial and collectors that are not US or State “signed” ?

    so every city and town in Va is responsible for their non-US/State signed streets and it is within their purview to prioritize bike/ped friendly if they so wish.

  2. The key hinge in the whole story is “change of culture”. I have been fortunate to visit Orange County, CA half a dozen times in the last few years for personal and work related trips. Most of the County has the appearance of being built in the last ten years. It hasn’t been, but some of it has. Driving through Irvine on many boulevards and streets one observes the beauty of a planned city. Beginning with houses on one side, you see a wide buffer of grass until the sidewalk, then another smaller buffer of grass, the curb, a bike lane, two or three lanes for vehicle traffic, a narrow grass strip with palm trees spaced every 20 feet or so, several lanes of traffic for the opposite direction, a bike lane, curb and narrow grass strip, sidewalk, wide grassy area, and then more homes. You think you’ve somehow been time warped. Depressingly you realize every place in America could have looked like this, less the palm trees, but instead look like Hull Street Road and its off shoots in Chesterfield County. Uuhhhhgggleeee!

    Beautiful! Someone not only thought ahead, but the designs of the urban planners are supported by the residents. Virginians overwhelmingly would not have wanted bike lanes built into the transportation swathe and considered them a waste of money. I would love to see them, somewhere, as I am scared to death to bike among Virginia drivers on almost all public roads. Luckily I’m a mile from a County park and can get there to bike a few miles with little car traffic.

    Multi-mode transportation and such “bizarre” concepts as pre-planned bike lanes have not fit into Virginia culture. One senses a slight shift and stirring of change, but few of us will be around to experience the end product of such thinking.

  3. another reform ….

    “Level Of Service D” Road engineers are trained to design for “Level Of Service D”. Like the grading scale in school, this is not a good grade, much less a worthy goal to shoot for. Level Of Service D means on average over a 24 hour period the traffic flows. (I am sure an engineer can quote the exact definition.) That means, in rush hour it can be total gridlock and at midnight, abandoned. This is an average for the day not the performance desired when we are actually using the roads rather than having nightmares about them. They design for failure. No wonder the roads are not functioning for us.

    • IF you want LOS A or B, it’s gonna cost you like the devil!

      how much unused pavement should we have – outside of rush hour?

      the other metric they use is V/C ratio. that’s Volume divided by capacity.

      when Volume exceeds capacity – the road is said to “fail” but “fail” does not mean the road ceases to exist… it just means you may have to wait through a light once or twice. …

      but congestion has a way of working itself out.. in a manner similar to tolls in that people who have the option will avoid congestion or tolls – and it’s more people that we think.

      very, very few people have absolutely no choice but to drive in the maw of rush hour – every day. it’s a choice of things like driving solo.. or not time shifting or heck.. just going out for Pizza at the worst time!

  4. Agree, the solution is not necessarily more pavement .. .that is what VDOT does though which is the point of the article. All the things you said are spot on. I have witnessed this VDOT “pave it over” thinking process first hand. In traffic network models they add future projected volume and, surprise, you get “red” (failed sections of the network). The solution? Just add lanes until the red goes away, and rely on roads that are not even approved or built yet. This I have witnessed first hand.

    • Important to realize that in 46 other states and in all of Virginia’s cities and towns and 2 Va counties – that the locality calls the shots on the local roads.

      The roads the cities and towns have less control over that do go through their jurisdictions are US signed roads and Virginia Primary roads.

      Both these kinds of roads were built originally to move traffic THROUGH the area to other cities – roads that originally were designed to function like interstates and still function as ways to get around the State when there is not an Interstate.

      So these are roads like U.S. 29, or 17, or US 1 or similar and VDOT’s mission is to keep these roads flowing as much as possible and when they don’t it creates a major block on a road that is supposed to convey people from one town to another …like US 29 in Charlottesville that is driving the impetus for a bypass to recover the utility of the original US 29 in moving traffic external to Charlottesville – traffic that originates outside of Charlottesville that is just to get to locations on the other side of Charlottesville by using US 29 through Charlottesville – U.S. 29 was built original for that purpose but then co-opted by Charlottesville as a local commercial venue.

      This was and is not uncommon. It’s evolves that way quite a lot but if the original road is no longer usable as a road “through” town that serves people trying to get “through” down .. then it usually motivates a bypass to return that utility, to rehabilitate that function.

      Think about the other places we travel that now have bypasses…and a good example is Lynchburg where US 29 used to go through Lynchburg City but became usable as a “through” road which basically cut people north and south of Lynchburg who needed to get through Lynchburg to get to their destinations.

      That’s why I asked earlier – for roads like US 29 – who built the original road and for what purpose and US-signed and Va Primary roads were never built to be city-streets with bike/ped, etc but rather thoroughfares for folks who did not live in that city – but were trying to get THROUGH the city.

      So.. a lot of road history has been lost or was never known to start with – with respect to US signed and Va Primary roads.

      http://en.wikipedia.org/wiki/United_States_Numbered_Highways

  5. I object to the opening line of today’s “Time to Overhaul Traffic Engineering Guidelines” indicating that “[e]mployees of Virginia Department of Transportation, like most transportation departments, see themselves as being in the profession of building roads for cars.” My sixth grade English teacher, Ms. Cordell-Robinson, who instructed me in the dangers of broad categorization, and I remind you of this precaution.

    As I am sure you know, VDOT policy enshrines bicycle and pedestrian accommodation as prescribed in our “Policy for Integrating Bicycle and Pedestrian Accommodations” adopted by the Commonwealth Transportation Board in 2004 and as further detailed in Section A-5 of our Road Design Manual. VDOT has developed a substantial amount of bicycle and pedestrian infrastructure under this policy.

    I note that this policy developed during Senator Warner’s administration. Whereas Senator Warner is an avid cyclist and enthusiastically promoted bicycle and pedestrian accommodation in his administration, perhaps the constituents of our current governor need to provide him with some additional encouragement on this matter. Your sponsor’s former associate in the deputy secretary role is ideally positioned to assist with this.

    Thank you for your continued interest in our transportation infrastructure.


    Thomas S. Miller, P. E.
    Assistant District Structure and Bridge Engineer

  6. Pingback: Complete Streets News – February 2014 | Smart Growth America

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