According to Wikipedia:
The term slug (used as both a noun and a verb) came from bus drivers who had to determine if there were genuine passengers at their stop or just people wanting a free lift, in the same way that they look out for fake coins—or "slugs"—being thrown into the fare-collection box.The original sluggers would poach riders from bus stops. After a while, slugging queues formed at park-and-rides (on the inbound) and areas with many offices like the Pentagon (on the outbound) and the system became self-reinforcing. Sluggers have an unofficial website now and the system has been around long enough that it is ingrained in a couple of areas. However, one of them may not be New York.
Emily Badger, now of The Atlantic Cities, wrote a long and interesting piece about slugging last year, which outlined several factors that have to be in place for slugging to work:
- The HOV requirement must be 3. HOV-4 is too cramped, and HOV-2 lacks a sense of security. (With three strangers in a car, even if one is crazy they'll be outnumbered.)
- The HOV lane has to be lengthy or have a high toll, and paralleling traffic has to be bad enough that it saves considerable time. In DC, the 95/395 corridor is one of the most gridlocked in the country, while the carpool lane sails along at freeway speeds. And misuse must be enforced.
- There needs to be a parallel transit system for backup, even if it is slower. Drivers and passengers will not always balance perfectly.
- Employment needs to be situated in dense urban nodes that draw workers from a highway corridor
- Some homogeneity in the workforce. For instance, everyone in DC works for Uncle Sam (or so it seems)
I would add that slugging also needs
- The existence of park-and-ride lots where riders can congregate (preferably with some amount of cover from the elements)
- Parallel transit can't be too fast, frequent or reliable, although it's rare to find fast, reliable and frequent transit in the US. (In other words, if there was a Metro Line along 395 which ran at 110 mph to the District, there would probably be fewer slugs. But since the transit options are a bus with a transfer to Metro, slugging is faster.)
- The end of the system has to be in a transit-served area; the transit, or even bike sharing, can provide a last mile solution from the slug lines (which are sort of like transit stations).
On the GW, high tolls are certainly in place, and there are savings to be realized with an HOV toll pass. However, the system lacks a few other features. There is no major employment density on the other side of the bridge. Well, there is, but not that many New Jerseyites drive there from the GW. There are no time savings for HOV travelers, either. There's nowhere to congregate (although this might change, according to the article). Once across the bridge, there is relatively easy access to a subway station, but getting back on the highway requires a couple of zigs and zags on surface streets to the Bronx. Once on the train, however, the A train runs express to Midtown, making the trip in 20 minutes, which is generally faster than driving. Also, there is no toll westbound, so there's no incentive to pick up a passenger and save.
What would it take for slugging to catch on on the GW? First, the police would have to stop ticketing people for picking up slugs. It would have to be a two-way system, which would require more tolling capacity. A dedicated, easy-on, easy-off slug facility or location would have to be found (in Manhattan, this could be a section of street, but it's harder on the interstate in Jersey). And to cap it off, I think the Port Authority would have to create free-flowing carpool lanes, to create a time incentive. This, too, would be tricky, because they'd have to extend across the Palisades (which often back up), but in doing so would extend beyond the market of available slugs. So, the GW might not be right for slugging.