is a traffic grade of f good enough for reston-final

7/28/2019 Is a Traffic Grade of F Good Enough for Reston-Final

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Is a traffic grade of F good enough for Reston?

Monday evening the Countys Department of Transportation (DOT) staff presented to the

Master Plan Task Force its latest analysis for traffic in Reston in 2030. The presentation was

based on the Task Forces current planning proposal for Reston near the Dulles Corridor, called

Scenario G. This scenario was necessitated by the abysmal failure of an earlier office-focused

development proposal, Scenario E, to handle traffic at Restons intersections.

The traffic impact analysis, using sophisticated traffic engineering modeling, shows that we can

routinely expect morning and evening peak period traffic at intersections along Restons major

streets near the corridor to earn a grade of F. Amazingly, thats actually a modest

improvement (8%) over the preceding scenarios grade that can only be described as F-.

Warning: This letter is a little long and traffic wonkish.

And, yes, for all practical purposes, that grade is very much like the one you, I, and our children

experienced going through school. An F means that an intersection fails to handle its traffic;

traffic is gridlocked. It is a level of service (LOS) metric that is part of a national urbantransportation standard most recently updated in 2010. There are basically two dimensions to

the metric: whether the intersection is at or over capacity and the duration of traffic delays at the

intersection. An F grade is given to intersections that are either over capacity or where

average traffic delays exceed 80 seconds. It means that:

Most cycles failto clear the queue. . . A (volume-to-capacity) ratio of 1.0 or moreindicates that cycle capacity is fully utilized and represents failure from a capacity

perspective (just as delay in excess of 80 seconds per vehicle represents failure from adelay perspective).

And DOTs analysis shows that Restons seven gateway intersections along the DullesCorridor under Scenario G would average well over two minutes each during peak periods. For


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example, the intersection of Wiehle Avenue and Sunset Hills would have an evening peakperiod forecast delay of 253 seconds. Yes, that is four minutes and 13 seconds to get throughthat intersectionon an average day. Today that intersection has an LOS E (55-80 secondsaverage delay) in the evening rush period, one-third to one-fifth what we can expect in 2030.

The four gateway intersections on Reston Parkway and Wiehle Drive at Sunset Hills andSunrise Valley Drive have an average peak evening rush period delay of about 152 seconds inScenario G. With the exception of Wiehle/Sunrise Valley, all these intersections are well intothe LOS F range; Wiehle/Sunrise Valley earns an LOS D. Today, only the RestonParkway/Sunrise Valley intersection among these four intersections warrants and LOS F ineither the morning or evening peak periods.

Forecast AM & PM Peak Period Delays at Key Reston Intersections,

Scenario G, 2030 (Seconds of Delay)

Peak Period Reston Parkway Wiehle DriveSunset

Hills

Sunrise

Valley

Through

Delay

Sunset

Hills

Sunrise

Valley

Through

Delay

Morning 153 102 255 145 140 285

Evening 217 155 372 253 53 306


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Can you imagine what traffic will be like with a little rain, sleet, snow or even a minor accidentalong the way?

If you happen to be traveling from north to south (or vice versa) in Reston (say, taking your sonor daughter to soccer practice on the other side of town), you can count on going throughseveral such intersections, particularly at Sunset Hills and Sunrise Valley along Reston Parkway

and Wiehle. Through delays at these four intersections average more than five minutes duringthe peak traffic periods.

These delays to not count what DOT calls spill back, the queuing of vehicles so badly on astreet that it blocks the preceding intersection. DOT will study this phenomenon before itsubmits its required report to the Virginia DOT. With three and four minute delays at these coreintersections, spill back will be a virtual pervasive certainty during peak periods. Indeed, it ispart of the definition of an LOS F. Traffic will move from gridlocked to a complete standstill.

Maybe more importantly, these adverse outcomes assume an aggressive County campaign ofinvestment in roadways, bus transit, bicycling and pedestrian access, and traffic demandmanagement (TDM) well beyond the current County plan. The big budget items include new

connections over the Toll Road for Soapstone Drive, Town Center Parkway, and South LakesDrive. It would also include a grade-separated crossing (an interchange) at the corner of FairfaxCounty Parkway and Sunrise Valley Drive. It also includes a grid of streets around the stations,a few street extensions (such as Pinecrest to Sunrise Valley Drive), and lane additions atgateway intersections. These roadway improvements alone would add well over a half-billion2013 dollars to the Countys transportation spending budget. And, of course, we havent begunto discuss who would pay for those improvements.

These disastrous traffic results are set against a current County-wide urban transportationstandard for Reston and other transit areas that now stands with an LOS target of D for itsroadwayswhich is about as high as urban area intersections ought to be. The Tysonstransportation plan calls for achieving a LOS target of E. Now Supervisor Hudgins has asked

the County staff to look at establishing a traffic standard for Reston similar to Tysons, whichlikely means LOS E. Even with LOS E, which the handbook characterizes as when thevolume-to-capacity ratio is high, progression is unfavorable, and the cycle length is long.Individual cycle failures are frequent, there is little prospect of Restons gateway intersectionsever achieving this standard no matter how much money and effort is put into it. It would be ahollow, cynical goal unless the County is willing to constrain station area development to permitit to occuran outcome it has not yet supported anywhere, including Tysons.

The one flicker of hope in all this forecasting is that DOTs tested level of traffic impact maybetoo high. As it normally does, DOT analyzed the traffic impact based on development reaching83.3% of the proposed Scenario G capacity in the station areas and a County version ofMWCOGs forecast for jobs and household growth beyond those areas. These forecasts are

likely too optimistic for the 2030 timeframe. Indeed, MWCOG is reducing its growth estimatesfor 2030 as it moves from Round 8.0 (the base for this traffic analysis) to 8.1 and now 8.2 of itsWashington area forecasts. Moreover, as we are all aware, sequestration and general federalausterity are likely to slow regional and local growth for at least a decade absent someunforeseeable circumstance. Nonetheless, at some point in timemaybe earlier, maybe laterthan 2030the number of jobs and residents in Reston will reach the levels DOT tested withthe traffic-stopping results they forecast.


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The result is that, even if Reston is lucky enough to obtain all the funding, build all the criticalroadway improvements, step up its transit program to meet an urban requirement, and completethe many pedestrian and bicycling pathways and lanes required, traffic across this communityduring peak periods will move from the difficult situation we face today to an impossiblecondition in the future. In the almost certain absence of at least some of these improvements,traffic conditions in Reston will be worse than forecast.

Is this F peak period intersection congestion condition good enough for Restonsmajor Dulles Corridor thoroughfares? Do we need to reduce planned growth to enablegreater mobility within Reston? What else can we do to prevent traffic failure?

Its your community; you decide. Once you have decided, let Supervisor Hudgins and RestonTask Force Chairman Patty Nicoson know what you think. Please add Heidi Merkel, the leaderof the Planning Staff effort supporting the Task Force, and me, RCAs representative to theTask Force to those communications, to your communications so we can represent your viewsaccurately in the Task Force.

Terry MaynardRCA Representative to the Reston Master Plan Task ForceReston Citizens Association (RCA) Board of DirectorsCo-Chair, RCA Reston 2020 Committee

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