# Introduction

Dynamic ridesharing is a form of transportation that leverages High Occupancy Vehicle (HOV) lanes to get commuters to their workplaces. This practice occurs around San Francisco, Houston, and Washington DC where it is known as slugging. Slugging is a symbiotic relationship in which drivers transport passengers for free to predetermined locations so that they can use HOV lanes. These lanes are restricted to cars with a certain number of passengers during rush hour and are less congested. Slugging saves participants gas money and time while simultaneously reducing traffic and carbon emissions. Slugging eliminates the need to plan formal carpools that are difficult to maintain. Despite the lack of organization and endorsement by the government, slugging has evolved into an orderly system with rules and etiquette.

# History
### Development of HOV Lanes

HOV lanes were first opened in Washington DC along I-95 and I-395 in 1969 and were restricted to buses. However, to conserve gasoline during the 1973 oil crisis, HOV lanes were opened to cars with passengers. Today, HOV lanes are primarily promoted as a means of reducing congestion. At first, four occupants were required in a vehicle to qualify for HOV status. In 1988 the standard was lowered to three.
In addition to the original I-95 and I-395 HOV lanes, there are now HOV-2 lanes on I-66, I-270, 267/Dulles Toll Road, and I-50 as well. All these HOV roads are major arteries into DC. HOV lanes account for 26% of morning rush hour traffic into Washington DC, including mass transit vehicles that use the lanes. A 2003 study indicates that trips on I-95/I-395 are twice as fast in HOV lanes than in non-HOV lanes and trips on I-66 are 50% faster.
HOV restrictions hold during rush hour periods, typically around 5:30-9:00 AM and 3:00-7:00 PM on working days. The exact timing varies with distance to DC since this affects peak demand for the road. Furthermore, HOV restrictions only apply in the direction of heavy traffic flow. The HOV requirements are regularly enforced with offenders receiving large fines. Repeat offenders may even receive points on their license. This enforcement generally keeps the HOV lanes free of single occupancy vehicles.
Critics argue that HOV lanes are underutilized and fail to compensate for the loss of speed in the non-HOV lanes.

### Development of Slugging

The advent of uncongested HOV lanes incentivized commuters to drive with passengers. Drivers who did not want to deal with the rigidness of pre-arranged carpooling began to pick up passengers from bus stops in order to use HOV lanes. Over time this process formalized with drivers picking up slugs at designated locations. A 1989 report notes the formation of the first slug line, although other sources claim it began even earlier. A Virginia Department of Transportation report suggests that by 1999 three thousand people were slugging during rush hour, accounting for 11% of the total HOV lane use. Nowadays David LeBlanc, author of Slugging: The Commuting Alternative for Washington DC, contends that slugging transports about 10,000 commuters daily.

### Etymology of Slugging

Before the creation of formal slug lines, commuters would wait at bus stops for potential drivers. Bus drivers, who could not distinguish between these free riders and regular bus passengers, would become frustrated when these people did not board the bus. The bus drivers called these fake bus passengers slugs, a term that also refers to counterfeit tokens dropped in a fare box.

# Logistics

Slug lines, which are the pick up points for slugs in the DC area, generally lie near public transportation lines. This provides slugs with an alternate means of transit in case they cannot get a ride to their destination. These points also have ample parking for slugs' cars.
As with other forms of public transit, slugs have maps designating the pick-up and drop-off locations. There are 39 established slug lines in the DC area. There are 25 morning slug lines that help commuters enter the city from the Virginia suburbs like Springfield, Woodbridge, Stafford, and Fredericksburg. Each line has unique operating hours based on its proximity to DC. Afternoon slug lines depart from locations around Washington DC and bring passengers back to Virginia suburbs, with each line focusing on specific suburbs.
Slugging does not require any registration or prior arrangements. Instead, a slug travels to a slug line during rush hour. Once there, the slug joins a line waiting for drivers. When drivers pull up they announce their final destination. Slugs join the appropriate car, with priority given to those at the front of the line. This process repeats at the end of the day. This boarding process proceeds without official regulation, much the same way that other types of public transit, such as metros and buses, load without direct supervision.

# Etiquette

Although slugging is an unofficial system, slugs and drivers follow a well developed etiquette. This etiquette details appropriate behavior both inside and outside the car. At pick up points, slugs organize themselves by destination, and drivers offer rides on a first-come, first-served basis. Drivers are also expected to wait in line to pick up slugs, so the practice of driving around commuter lots to pick up stray slugs is frowned upon. Drivers generally only gather enough slugs in their car to meet HOV requirements; however, participants of slugging never leave a female slug alone at night.
Inside the car, both drivers and slugs must respect each other’s privacy and solidarity. Participants of slugging do not exchange names or talk unless the driver initiates conversation.. Conversation is limited and never includes controversial or personal subjects (e.g., politics, religion, family problems). The driver is the only person who can change the radio or temperature controls. Slugs do not hold phone calls during the ride as a sign of respect for the driver. Both drivers and slugs thank each other at the destination, but the parties never exchange gifts or money. Compensation is neither offered nor desired by either party as both slugs and drivers benefit equally from the system. Although these rules are not officially enforced, the community of slugs and drivers follow the etiquette for fear of being known as a bad commuter. Since both slugs and riders use the system daily, reputations are based on how well a participant follows this etiquette. In some locations, reputations can be damaged by on-line forum posts warning other participants of dangerous drivers and rude slugs.
The slugging etiquette may seem stifling, however, much of it is derived directly from etiquette found in official forms of public transit. There is a general understanding that the commuters are in a public space that by definition people only occupy because they are trying to get somewhere else; the transportation is being used as a means to an end, not an end in of itself. Consequently, it is understood that passengers should be allowed to engage in individual tasks without being bothered by other riders.

# Participants
### Drivers and Passengers

Slugging is symbiotic because both groups are performing a service for each other. Passengers allow the driver to utilize the HOV lanes, thus avoiding traffic while the drivers offer riders free transportation. Drivers and riders generally come from similar backgrounds and are typically between the ages of 25 and 34.
About 60% of people who participate in slugging do so only as passengers. Slugs face several risks; there is a possibility that they may not get a ride at all, and since they are riding with strangers there is a personal safety risk. However, only 11% of passengers mention riding with strangers as a fear associated with slugging, and this is mainly due to uncertainty about driver competence. About 28% of people choose to participate in the slugging system solely as drivers. As with passengers, the reduced commute time is the most important benefit they receive from slugging. The main reason stated for being a driver rather than a passenger is the flexibility it allows for people to leave earlier or later than others. Both groups mention the lack of formal carpooling arrangements and the lack of social interaction as benefits of the system. The biggest downside for participants is the time wasted waiting in line. This is a problem that can be found in most official modes of public transit.
From an outsider's perspective, the slugging system may seem extremely risky. However, there has been only one documented incident of harm to a slug. A motorist angrily hit a slug after the slug attempted to take a picture of his license place due to his erratic driving.

### Government

Washington DC area governments generally approve of slugging. They view it as a system similar to public transit. While the slugging system is dependent upon infrastructure paid for by the government (e.g. HOV lanes, Metro stations, etc.), once these structures are in place, slugging forms spontaneously. Therefore, most local transportation departments favor slugging and some actually work to support it. Some government officials are concerned that slugging does not actually reduce overall traffic. They claim that slugging merely steals riders off public transit systems, thereby not only reducing government revenue, but also remaining ineffective in the fight against road congestion.
The government is not able to actively endorse slugging. The Virginia Department of Transportation provides information on slugging but states that it does not accept any liability and cannot encourage people to travel with strangers. However, the growth of slugging has caused some commuters to ask for the government to become more involved and supportive. Currently DC police ticket drivers that stop on the side of the road to pick up slugs. Although the placement of the slug lines leaves drivers little choice, law enforcement officials cannot ignore their risky behavior. Thus, commuters have asked that the DC Department of Transportation help find better locations for slug lines.

# Future of Slugging
### Tolls

In 2015 construction of a new High Occupancy Toll (HOT) lane system on I-95 will be complete. HOT lanes allow single-occupant vehicles to pay a fee to use HOV lanes. Many slugs believe that these lanes will destroy the slugging system as drivers may choose to simply pay the toll rather than stop for passengers. Also, since HOT lanes are open to more users, the amount of time saved by slugging may be reduced.
In 2010, the San Francisco rideshare system faced the introduction of tolls to the HOV lanes. This raised many questions about whether and how money should be exchanged to pay for these tolls. While the exchange of money would violate one of the central tenants of slugging, the absence of driver compensation seemed to create an unequal system. As of 2013 the protocol for money exchange has still not been solidified within the community.

### Hybrid Vehicles

Hybrid vehicles threaten the slugging system because they are allowed to use HOV lanes regardless of the number of passengers. Washington DC's market for hybrids is comparable to California and most consumers cite the HOV lane exemption as the reason for a hybrid purchase. Hybrid vehicles have caused the congestion in HOV lanes to increase and sometimes be just as congested as regular lanes. Participants of the slugging system advocate ending the hybrid HOV lane exemption and increasing fines for HOV lane violators.

### Technology

Increases in smart phone technology and usage provide an opportunity to match slugs with rides more efficiently. Text message listserves already exist on some slug lines and allow participants to gauge the current status of the line.

# Types of Ridesharing

Slugging, carpooling, and hitchhiking all provide means to increase car occupancy and efficiency. Yet there are vital differences between the three means of transport. Traditional carpooling differs from slugging in that it is a recurring, consistent arrangement that has a fixed group of members and a set schedule. The downsides of traditional carpooling include its rigid schedule and the potentially awkward reimbursement of the driver.
Distinctions between slugging and hitchhiking differ in the types of people they serve. Sluggers in the DC area are generally federal employees or civilian contractors belonging to the upper to middle class. This homogeneity may contribute to the success of dynamic ridesharing in this area. In contrast, hitchhiking has declined due to fears of dangerous hitchhikers whose backgrounds are highly varied. Slugging is a unique situation where structured rules and working class participants decrease the perceived risk.

# Alternative Carpooling Initiatives

DC Metropolitan area transit authorities have created a program called Commuter Connections, which encourages commuters to use alternatives to single occupancy vehicle transit. Commuter Connections maintains a ride board that allows strangers to organize carpools to work, similar to slugging. Carpools can be organized in a variety of ways including alternating drivers and riders and pick-up at various locations. If there is a designated driver, the passengers are expected pay for gas and parking. Etiquette can also vary and is decided upon by each group of carpoolers. In addition, this program offers a guaranteed ride home to increase flexibility for participants. Commuter Connections offers tools and incentives for entire companies that join the program. They also disseminate information for commuters interested in bicycling, walking, or taking public transportation to work.

# Conclusion

The popularity of traditional carpooling has declined over the last 30 years despite direct attempts to encourage ridesharing. The reduction of gas costs did not give commuters enough of an incentive to participate in such a rigid system. However, with the invention of HOV lanes, carpooling became a viable method of reducing commuting time. This benefit made dynamic ridesharing a more desirable transit choice by tapping into people's natural, internal motivation to save time.
Energy efficient home products are an example of a federal policy that uses extrinsic incentives to internally motivate a change in behavior. In 2005, homeowners with windows meeting Energy Star standards were eligible for $200 tax breaks. At this time, the nationwide Energy Star window market share was 49%. In 2009, the incentive increased to $1500 and by 2010 the Energy Star window market share increased to 93%. By increasing monetary incentives, the federal government was able to get closer to its policy goal of increasing energy efficient products in American homes.
Even with the strong internal motivation enabled by the slugging system, it is still interesting to see how at ease people are with slugging. In a society that preaches distrust of strangers, how do sluggers participate comfortably in this risky system? Similarities between official modes of public transportation and slugging show that much of the mental model built by the former holds true in the latter. Specifically, both have designated pick-up and drop-off locations, methods of boarding and disembarking, and rules of conduct that make the system operate safely and effectively.
The idea that mental models can be used to help participants internally legitimize risky systems can be seen in phenomena besides slugging, such as online education. One risk of online education is that outsiders may not view the system as a valid form of eduction, so any degree earned this way is subject to skepticism. Online universities lower the perceived risk by promoting aspects of their system which mimic those found in the mental model of traditional education. Online schools will advertise small class sizes, student orientation, alumni support networks and their physical locations. All of these are relevant to traditional education, so people take comfort in their presence in the online system whether or not they actually affect the value of the education.
It is recommended that future researchers look further into dynamic ridesharing elsewhere in America and internationally.

# References

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* ↑ Katherine F. Turnbull. "History of HOV Facilities". Federal Highway Administration (FHWA). Retrieved 2012-04-26. Complete account published in Katherine F. Turnbull (1992), "HOV Project Case Studies: History and Institutional Arrangements"
* ↑ Spielberg, F., Shapiro, P., 2000. Mating habits of slugs: dynamic carpool formation in the I-95/I-395 corridor of Northern Virginia. Transportation Research Record 1711, 31–38.
* ↑ History of HOV Lanes http://trafficbulldog.org/news.php?nid=4
* ↑ Federal-Aid Highway Program Guidance on High Occupancy Vehicle (HOV) Lanes http://ops.fhwa.dot.gov/freewaymgmt/hovguidance/chapter2.htm
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* ↑ Second Report on the High-Occupancy Vehicle Enforcement Task Force http://testvirginiadot.org/news/resources/HOV_Task_Force_Rep Pretty Minort_1-4-05.pdf
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* ↑ HOV Lanes in California: Are They Achieving Their Goals? http://www.lao.ca.gov/2000/010700_hov/010700_hov_lanes.html
* ↑ Spielberg, F., Shapiro, P., 2000. Mating habits of slugs: dynamic carpool formation in the I-95/I-395 corridor of Northern Virginia. Transportation Research Record 1711, 31–38.
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* ↑ BMI, 1999. I-95/I-395 HOV Restriction Study: Summary Report. Virginia Department of Transportation.
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* ↑ Hendel, J. (2011, August 8). Slug life: Pick up these roadside commuters to ride the hov lane. Retrieved from http://www.tbd.com/blogs/tbd-on-foot/2011/08/slug-life-pick-up-these-roadside-commuters-to-ride-the-hov-lanes--12233.html
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* ↑ LeBlanc, D. (2013). Message Boards. Retrieved from http://www.slug-lines.com/forum2/forum.asp?FORUM_ID=2&sortfield=lastpost&sortorder=desc&whichpage=3
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