Slug line

Thoroughly updated 8/5/2018:  As it turns out, there’s an app for that.  And a modern slug is a well-organized slug.

On this page, I argue that maybe the best commuter use of the Mill Street garage is to make it the base for the first successful I-66 slug line from Vienna.  And that the Town should work to make that happen.   The question I address here is, could that work?

Little about the Mill Street Garage makes sense to me.  You can read that here.  If the commuter uses as proposed by Vienna are unlikely to bear fruit, is there any better way to make this new Town-owned facility serve commuting needs of Vienna citizens?  My answer is:  let’s see if it will work as the base for a Vienna I-66 slug line.

A slug line occurs when slugs (who want a ride downtown) gather in some known location to meet drivers (who want passengers in order to meet HOV restrictions).  Unlike traditional carpooling, the match between car and passenger is on-the-fly, first-come, first-served.  There’s no scheduling and no guarantees.  It is “informal carpooling”.

The slug line is indigenous to Northern Virginia.  For those of you who didn’t grow up here, or are too young to recall the Arab oil embargo, slug lines developed spontaneously along the I-95 corridor in response to gas rationing (!), high gas prices, and HOV (4!) restrictions along the Shirley Highway. (Just read the slug line link above. It’s a nice bit of local history.)  And they are still going strong on the I-95 corridor.

Slug lines are developing now, on the I-66 corridor, in part due to the high tolls on the HOV portion of I-66.   Vienna already has a slug line, from the Vienna Metro South parking lot to DC.  This slug line was started in 2016, but it does not appear to be very successful.  At least in part, that appears due to the need to  fight traffic to get to the Metro station.

The financial incentives for slugging seem to be in place now.  Just check out the sign in this link.  For the want of one passenger (HOV-2) you may pay a substantial toll to take I-66 into town.  Looking forward, the planned HOV-3 toll lanes on I-66 outside the beltway will add further incentive to Vienna-based slugging.  As with the other high-occupancy toll (HOT) lines in the area, the toll will vary based on time of day and traffic load.


Let me describe how it might work, and then talk about the barriers to making it work.

First, the Town adds a nice outdoor canopy in front of the building.  People who want a ride downtown, on I-66, park in the Mill Street garage and line up.  That’s the slug line.  People who need a rider to get HOV-2 down I-66 swing by, pick up a rider, and are on their way.  The Town does its best to advertise that this is happening.  If the 60 free spaces from the TOV lot are taken up, presumably the building owner can charge some modest fee to park in the other 120 in the basement of the building.  Maybe Vienna residents get first crack at the free spaces, since we paid for them.  The local coffee shop sets up a cart to cater to the line.  The drivers gets down I-66 toll-free, the riders get down I-66  free, period, the coffee shop owner gets some early business, the building owner gets some modest income off the overflow parking.  The brutal I-66 tolls do what they are supposed to do — get cars off the road.  And the tiny little Town of Vienna takes a leadership position in reducing traffic congestion.

And then the unicorns dance across the rainbow that forms over the new garage, and we live happily ever after.


Back in the real world, the first problem is getting back home.  Existing suburban morning slug lines have return afternoon slug lines in DC.  The locations for the return slug lines are well-established.  (See dropoff points below).  It would just be a question of having adequate volume of slugs and drivers bound for Vienna.  Separately, there’s the question of getting back to Vienna if there are no drivers.  You could take Metro with a bus connection to get back to the Mill Street garage, but that’s pretty slow.  (I.e., if you wanted to do that, why are you slugging in the first place?)  There are also guaranteed-ride-home programs , as described on this page.

In the modern world of Uber and Lyft, could there be an app for that?  Sure, that’s already been done.  It’s called — almost inevitably  — SmartSlug.  I have no idea how well it works, but the point is to let drivers know how many slugs are waiting at any given location.  Barring that, a web-enabled camera (inevitably called SlugCam) would be adequate for letting slugs and drivers know the size of the slug line.

The second question is, where in DC would you be dropped off?  The original slug lines had a handful of well-defined high-volume destinations, including foremost the Pentagon, and then a handful of Metro stations.  In theory, the current Vienna Metro slug line has five potential dropoff points, but the volume of riders appears to be low:

Third, is Vienna just too affluent for slug lines?  Are the people paying those $40/day tolls just so well-off they don’t care?  Are typical downtown commuters indifferent to getting to DC for free?  That’s hard to answer.  The original slug lines were definitely a middle-class solution to a pressing financial problem.  Maybe Vienna is too well-to-do to for slugging.

Fourth, is there backup in-bound transport for unmatched slugs?   The nearest Metrobus stop is a quarter-mile away, with buses running to the Vienna Metro every half-hour.   Maybe that’s adequate.  Maybe not.

Finally, the key question is whether the potential slug and driver populations are large enough.  The advantage of the slug line is that you don’t have to coordinate with some other person.  It’s first-come, first-served.  But that only works well if there are enough slugs and enough cars, arriving at a steady enough rate, that the wait time is reasonable.  With sixty Town parking spaces,  that may simply be too few slugs to support a viable slug line.

Those living east of Mill Street would seem to be the natural target audience for this.  Traffic is no morning barrier to getting to Mill Street in the morning, and those individuals would likely drive past Mill in the evening anyway.  There’s no shortage of potential drop-off points on the south side of Maple for the evening trip.

Traffic is a barrier for those living west of Vienna.  For those heading to I-66, the leg of the trip between Nutley and Mill Street represents additional time.  And that stretch of road can frequently be congested.

Whether slugging is worthwhile to local drivers is an interesting economic question.  With light traffic, the round-trip from Nutley to Mill will take little time, but the I-66 toll will be low.  As traffic builds, both the time cost for swinging by Mill and the I-66 toll will rise.  At what points along the way is worth enough, to enough drivers, to spend X minutes getting to Mill and back, to save $Y in I-66 tolls?


At any rate, that’s my take on it.  There’s just  not a lot of value-added evident in driving to that garage and parking, mid-commute, as the Town suggests.  That will cost precious morning commute time, and doing that makes no sense unless there is some substantial advantage offsetting that time cost.  Getting downtown much faster than bus-to-Metro is one, and avoiding the I-66 toll is another. That’s where I see enough value added to make it worthwhile to break your commute into two pieces.

The high I-66 tolls tell me there may be a deal to be made in creating the first successful slug line from Vienna.  The construction of HOV-3 HOT lanes on I-66 outside the beltway should add demand for slugging.  I don’t know if it’s even remotely plausible to encourage a slug line to form around the proposed Mill Street garage, but it’s my best guess for making the garage we just bought serve the purpose the Town said it was for.

That is just such a ho-hum ending, let me jazz it up with a little buzzword salad.

Slugging is a technology-driven platform connecting commuter-partners in a symbiotic, synergistic slug-driver relationship.  It is the sharing economy’s  answer for niche de-commercialization of the Uber/Lyft model.  Payment-free, commitment-free, it offers an impactful and vibrantly granular team-driven commuting experience.  An outside-the-box leveraging of Vienna’s core competencies — traffic and parking — slugging is nothing less than a bleeding-edge disruptive and vibrant paradigm shift.  As car-free Millenials become the new normal, it provides the hyperlocal, proactive, and holistically sustainable lower-carbon solution to the logistics of commuting.