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Coordinating, Developing, and Delivering Highway Transportation Innovations

This report is an archived publication and may contain dated technical, contact, and link information
Publication Number:  FHWA-HRT-12-053    Date:  November 2012
Publication Number: FHWA-HRT-12-053
Date: November 2012


Casual Carpooling Scan Report

Houston, TX, December 5–6, 2010

The scan group arrived in Houston on the evening of Sunday, December 5, 2010, and stayed in the western suburb of Katy, TX. On Monday morning, group members visited three different slug line origin locations in the Houston region: Kingsland Park-and-Ride lot (see figure 6), Addicks Park-and-Ride lot, and Northwest Park-and-Ride lot (none of the group members visited all three individually but collectively all three locations were visited).

A black car is parked at the curb of a median and two men are standing next to the car on the median. Two concrete supports of what appears to be an overpass are on the median. Beyond the median is a parking lot filled with cars. Sunlight is streaming in: the sun is either rising or setting. Trees can be seen in the distance.

Figure 6. A vehicle waits for slugs at the Kingsland Park-and-Ride lot in suburban Houston, TX.

Various members of the group slugged into downtown Houston from each park-and-ride location. Nader Mirjamali (Project Manager, High-Occupancy Toll (HOT) Lanes) of Houston METRO (Metropolitan Transit Authority of Harris County, Houston, TX) met the group at the Addicks Park-and-Ride lot (see figure 7) to orient group members and to explain how slugging works in Houston. Mirjamali often makes his personal commute to work via slugging and thus had an extra measure of insight into the practice. At the bus shelters in each park-and-ride lot, Houston METRO has installed signs and demarcated separate waiting areas for the slugs to queue for rides. Rider volume in the Houston lines was rather small for the duration of the groups’ observation (with rider and vehicle queues never exceeding the single digits). Most vehicles tended to pick up just one passenger, consistent with the new rules allowing free travel during most times with two-person carpools, although the group did observe a few vehicles picking up two passengers (and one vehicle even picked up three).

. A white SUV is parked at the curb of a median at a Park-and-Ride lot.  The median is lined with various street signs: two yellow crosswalk signs and a 10-mile an hour speed limit sign. Waist-high metal fences line the median, indicating where people can line up to wait for rides. Three people are lined up behind the fence. The person at the front of the line is trying to get the attention of the driver of the SUV by holding up his finger. Above the median is a weather shelter that covers the median and extends over the curb to cover cars as well.

Figure 7. A vehicle picks up slugs at the Addicks Park-and-Ride lot in suburban Houston, TX.
Scan member Peter Valk holds up his index finger to inquire whether the driver will take one more passenger.

The Katy Freeway (along which two of the slug line locations sit) underwent major changes within the past 2 years. Additional lanes were added, and the limited access portion was changed from HOV to HOT status. The Katy Freeway now has nine lanes in each direction (three frontage lanes, four general purpose, and two managed HOT lanes), which has significantly increased the capacity of the roadway and reduced congestions on the general purpose lanes. This probably helps to explain the low-slugging volume, as carpools now offer little time savings. (It was confirmed through independent research by Dr. Mark Burris, a scan tour participant, that slugging volume in Houston has decreased by 50 percent.) The HOV discount on the Katy HOT lanes is now available from 5 a.m. until 8 p.m. (15 hours per day).

On the Katy Freeway, drivers have three options, as follows:

Drivers may vary their behavior depending on their time of departure, traffic conditions, and whether they are in a hurry.

The group members individually slugged into downtown Houston and reconvened to relate and discuss their slugging experiences. The unwritten rule for slugging drivers in Houston is that they are presumed to be willing to drop off their passengers anywhere that the commuter buses make drop-offs along Smith Street (an 18-block length from Franklin to Pierce Streets). At times, before a passenger enters a vehicle, the driver will inquire how far down Smith Street he or she needs to go, after which the driver may then elect not to take a passenger who wants to be dropped off beyond the driver’s destination.

At mid-morning, the team made its way to the Houston METRO offices to meet with Mirjamali and Vincent Obregon (Associated Vice President, Capital Program Implementation). Mirjamali and Obregon briefed the group on the history of slugging in the area, METRO’s thoughts about the practice, and plans for other highway projects in the area. METRO tolerates slugging and even helps facilitate it in small ways, such as by providing designated waiting areas at the park-and-ride lots, so long as it does not interfere with their commuter bus operations and that plenty of parking spaces remain available for the bus users. Mirjamali and Obregon estimated that their average fare box recovery for the commuter buses was 20 percent. The full one-way fare to ride a commuter bus can cost up to $4.50, although many employers help reimburse that cost. During the peak travel time, the commuter buses run on 4-minute headways; thus, individuals spend very little time waiting. The Houston region has plans to convert more than 129 km (80 mi) of HOV lanes to HOT lanes by the beginning of 2013.

One METRO employee noted his personal motivation for slugging rather than taking the commuter bus (which he could do for free as a METRO employee) is that the METRO headquarters sits at the end of the bus route and he would have to wait for the bus to make multiple passenger drop-offs before it arrived at his destination. This extra time spent waiting justified the mode switch to slugging for him.

A white bus with red and blue stripes approaches a bus shelter on a downtown city street. A line of about four people has formed at the shelter. White skyscrapers can be seen on both sides of the street; a glass skyscraper across the street reflects the scene.

Figure 8. A Houston METRO bus picks up passengers for the afternoon commute along Louisiana Street downtown.

In the afternoon on the same day, the scan group went to Louisiana Street, the major outbound downtown thoroughfare parallel to Smith Street, to try to locate slugs making the return commute. Afternoon slugging in Houston is much less prevalent than is morning slugging. As shown in figure 8, instead of slugging, many commuters will take a commuter bus back to the park-and-ride lot. The group only saw one dynamic ride–match occur. A pick-up truck drove up to the commuter bus stop, and the driver asked if anyone was headed to his particular park-and-ride lot. One of the people in line answered in the affirmative and got in. The scan group did not attempt to slug back out to the park-and-ride lots (as passengers) from downtown. The group, however, did pick up a slug from the bus line and drove her to the Northwest Park-and-Ride lot, which is located near the airport. The woman was very helpful in telling the group about slugging and was also invaluable in guiding the group out of downtown and onto the HOV lanes (see figure 9). This raised another interesting question about roadway and transit system literacy. If it had not been for the slug who guided the scan group, they would have been at a loss in trying to access and use the HOV facilities. Driving slugs requires a thorough knowledge and experience with the Houston transportation infrastructure (especially because there is no informational Web site for Houston slugs). The Houston HOV and HOT networks appeared to be especially complex.

Photo of a highway on a cloudy day. Traffic is oncoming on the left side and is outgoing on the right. There is little traffic on the left; the traffic on the right is very congested. Between the oncoming and outgoing traffic is a center limited-access lane. Traffic in this lane is outgoing, but is less congested than the right lane. Above the limited-access lane is a traffic light and signs on either side (the signs are too blurry to read). There are billboards and exit signs on both sides of the highway. Light posts can be seen on the left side of the photo, but the lights do not appear to be on. Two large telephone towers are on either side of the highway, with telephone lines crisscrossing the skyline.

Figure 9. View of limited-access westbound HOV lane on the Northwest Freeway outside of Houston, TX.

Summary of Lessons Learned and Analysis of Practices

Time savings is a significant factor for passengers who decide to slug. Congestion has been reduced in recent years because of the improvement made to the Katy Freeway. Because there is no longer a strong time savings incentive to slug over taking transit or even driving alone, there are fewer slugs. There are significant numbers of transit riders paying to ride the bus from the same lots. Drivers continue to save toll money on the Katy Freeway because it is a HOT facility.

Unique to Houston is that slugs use large and visible park-and-ride lots that were established for transit riders. The park-and-ride lots have dedicated entrance and exit ramps from the freeways, making it extremely convenient for drivers to exit the freeway, pick up passengers, and return to the freeway. Despite this convenient infrastructure, the slugging population remains small. It would be interesting to know what impact this infrastructure could have on making slugging more convenient in other regions. Although it does not seem to be a factor in Houston, the lack of parking at the pick-up location, or rather the lack of safe and convenient parking, may be a factor in expanding slugging to other corridors.

Unlike in other cities, the number of people slugging was insignificant compared with the number of commuters taking the express buses, despite the $4.50 one-way bus fare. There was no observation of anyone in the bus line slugging instead of taking the bus, but it was early and only a few cars were driving by looking for passengers. Therefore, waiting for a car ride might not have been an attractive proposition at that time but might have been later in the commute period. Dr. Mark Burris, the scan team’s expert on Houston slugging, indicated that based on his experiences from focus groups in the Houston metropolitan area, he would be surprised if many people passed up the bus en route home, noting that even the more dedicated slugs would use the bus on the trip home unless a car came by first.

Safety concerns remain a factor. The scan group observed that a handful of drivers picked up more than one passenger, even though the requirement was only HOV-2, and stated that they did so because it seemed safer. The female passenger that the scan group picked up during the afternoon peak hour stated that she agreed to ride with the group because it was a group and there was one female in the group. Although there is no available approximation of the percentage of drivers who take more than one passenger, even though they are not required to for HOV access, future dynamic ridesharing systems or slugging efforts could consider how to encourage multiple passengers pairing with a single driver.

Anecdotally, it appeared that many of the Houston slugs were long-time participants from when there was a single HOV-3 lane and were still slugging out of habit after a second managed lane was added and both lanes became HOT-2 lanes (meaning carpools with as few as two participants could use the managed lanes for free, whereas those driving alone could pay to use them). There did not appear to be many new participants, however, which is probably because getting into a car with only one other person—the driver—may be perceived as dangerous by someone who has not previously slugged and also because most of the incentive was removed when the Katy Freeway improvements were made. In general, out of the three cities studied, slugging is least developed in Houston, both in terms of gross number of participants and in the extent of the origin and destination network.


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