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showed the average walk from a parked auto to the carpool formation site to be 1.75 minutes fol- lowed by an average wait of 2.4 minutes (Burris and Winn, 2006). Casual carpooling is believed to have come to Houston around 1990, focusing on the Addicks park- and-ride lot and bus terminal on the I-10W Katy Freeway HOV facility at the western fringe of the city (Wall, 2002). It has since spread to the Kingsland park-and-ride along the same HOV facility and to the Northwest Station park-and-ride on US 290 Northwest Freeway (Burris and Winn, 2006). Advent of the QuickRide program, whereby 2 carpools may for a fee enter the I-10W and US 290 HOV facil- ities during hours they are otherwise restricted to 3 occupancy vehicles, has led to surveys of QuickRide participants. A question inquiring about QuickRide participants' usual carpool partner pro- duced a finding that 7 percent were slugs (Burris and Appiah, 2004). This number is not directly trans- latable to the carpool makeup of all carpools on Houston HOV facilities, but it gives what is almost certainly a conservative indication of casual carpooling on the Katy and Northwest facilities. Travel time savings indicated in Table 2-21 for the I-10W and US 290 HOV lanes are 17 and 22 minutes, respectively. The measurements made in 2003 were used to estimate casual carpool net savings over SOV driving of 6 to 13 minutes at 7:30 AM, the time of maximum savings, at the three Houston park- and-ride sites identified above. Net savings over express bus were 2-1/2 to 3-1/2 minutes (Burris and Winn, 2006). Effects of Casual Carpooling. There are mixed reactions as to whether the relationship between casual carpooling and public transit are symbiotic or parasitic. Some transit operators simply regard sluggers as lost fares (Spielberg and Shapiro, 2000). On the other hand, casual carpooling eases peak crowding on buses and trains, which in turn may possibly encourage new transit users (Rides for Bay Area Commuters, 1999) and/or may reduce the number of peak buses that must be assigned to one of the most expensive of bus operations: peak-hour, peak-direction express bus service (see Chapter 4, "Busways, BRT and Express Bus," under "Related Information and Impacts"--"Costs and Revenues"). The prior or alternative mode makeup of sluggers seems to be less conducive to vehicle trip reduction than the broader universe of HOV facility users (see "Related Information and Impacts"--"Sources of HOV Users"--"Mode Shifts" below). RELATED INFORMATION AND IMPACTS HOV Facility User Groups HOV facilities serve multiple user groups, both in terms of shared-ride travel modes and travel markets. Carpools, vanpools, and buses are all authorized to use most HOV facilities and thus con- stitute shared-ride travel modes. The exact mix of travel modes varies by project, however, depending on the orientation of the lane, the travel and land use patterns in the area, the level of transit service provided, and the carpool occupancy requirement. User Distribution among Modes Table 2-23 illustrates the mix of bus, carpool and vanpool vehicles, and the corresponding person volumes and primary modal distribution using the examples of HOV lanes from Table 2-22. As discussed with reference to Figure 2-3, projects with the higher bus volumes tend to be the ones with substantially higher overall person movement in the HOV lanes. HOV lane vehicle and per- son volume totals, along with AVOs, are also provided in Table 2-23 as a convenience. 2-71

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Table 2-23 Examples of Vehicle and Passenger Mix and AVOs on HOV Facilities in the AM Peak Hour HOV Facility Vehicles HOV Facility Persons HOV Facility Data Buses Pools Veh. Buses Pools Pers. AVOs HOV Facility Year No. Pct. No. Pct. Total No. Pct. No. Pct. Total Bus Pool Total Alameda Co., CA I-80 Bay Br. 1989 101 4% 2,325 96% 2,426 3,535 30% 8,273 70% 11,808 35 3.56 4.87 Boston, I-93 North 1999 35 3% 1,016 97% 1,051 1,050 31% 2,320 69% 3,370 30 2.28 3.21 Dallas, I-30 R.L. Thornton 1996 64 5% 1,197 95% 1,261 1,041 29% 2,494 71% 3,535 16 2.08 2.80 Dallas, I-35E Stemmons Fwy. 1998 9 1% 795 99% 804 310 16% 1,667 84% 1,977 34 2.10 2.46 Dallas, I-635 LBJ Fwy. 1998 1 0% 849 100% 850 10 1% 1,812 99% 1,822 10 2.13 2.14 Denver, US 36 Boulder Tpk. 1989 28 100% 0 0% 28 1,000 100% 0 0% 1,000 36 -- 36 Hartford, I-84 1998 12 2% 540 98% 552 288 19% 1,193 81% 1,481 24 2.21 2.68 Hartford, I-91 1998 11 2% 641 98% 652 280 17% 1,416 83% 1,696 25 2.21 2.60 Houston, I-10 Katy Fwy. 1998 40 4% 895 96% 935 1,355 39% 2,091 61% 3,446 34 2.34 3.69 Houston, I-45 Gulf Fwy. 1998 31 2% 1,299 98% 1,330 740 22% 2,682 78% 3,422 24 2.06 2.57 Houston, I-45 North Fwy. 1998 53 4% 1,341 96% 1,394 2,100 44% 2,725 56% 4,825 40 2.03 3.46 Houston, US 290 Northwest 1998 22 1% 1,521 99% 1,543 1,035 25% 3,030 75% 4,065 47 1.99 2.63 Houston, US 59 Southwest 1998 38 3% 1,466 97% 1,504 1,420 31% 3,147 69% 4,567 37 2.15 3.04 Los Angeles, I-10 San Bernardino 1989 71 5% 1,374 95% 1,445 2,750 39% 4,352 61% 7,102 39 3.17 4.91 Marin Co., CA US 101 1989 57 8% 678 92% 735 1,995 57% 1,490 43% 3,485 35 2.20 4.74 Minneapolis, I-34W 1998 15 2% 731 98% 746 469 26% 1,318 74% 1,787 31 1.80 2.40 Minneapolis, I-394 (inner) 1998 56 3% 1,618 97% 1,674 1,834 35% 3,341 65% 5,175 33 2.06 3.09 Minneapolis, I-394 (outer) 1998 29 3% 885 97% 914 1,031 36% 1,797 64% 2,828 36 2.03 3.09 Montreal, Champlain Bridge 1992 91 100% 0 0% 91 5,300 100% 0 0% 5,300 58 -- 58 New Jersey I-287 1998 2 1% 352 99% 354 45 6% 711 94% 756 23 2.02 2.14 NJ Rte. 495 (to Lincoln Tunnel) 1989 725 100% 0 0% 725 34,685 100% 0 0% 34,685 48 -- 48 New York City, Gowanus Expy. 1989 202 54% 173 46% 375 8,686 91% 899 9% 9,585 43 5.20 26 New York City, I-495 L.I. Expy. 1989 165 44% 214 56% 379 7,838 95% 394 5% 8,232 48 1.84 22 No. VA/DC I-66 1998 16 0% 3,405 100% 3,421 484 7% 6,486 93% 6,970 30 1.90 2.04 No. VA/DC I-95/I-395 Shirley 1998 118 4% 2,654 96% 2,772 3,085 27% 8,212 73% 11,297 26 3.09 4.08 Norfolk, I-64 1989 0 0% 930 100% 930 0 0% 2,130 100% 2,130 -- 2.29 2.29 Norfolk, Va. Beach, SR 44 1989 0 0% 800 100% 800 0 0% 1,520 100% 1,520 -- 1.90 1.90 Pittsburgh, I-279/579 1989 23 3% 845 97% 868 1,050 41% 1,527 59% 2,577 46 1.81 2.97 Santa Clara Co., CA SR 237 1989 18 2% 754 98% 772 630 27% 1,720 73% 2,350 35 2.28 3.04 Santa Clara Co., CA US 101 1989 3 1% 376 99% 379 105 12% 803 88% 908 35 2.14 2.40 Seattle, I-5 North 1992 64 5% 1,169 95% 1,233 2,605 46% 3,039 54% 5,644 41 2.60 4.58 Seattle, I-5 South 1992 28 7% 400 93% 428 1,176 47% 1,320 53% 2,496 42 3.30 5.83 Seattle, I-90 1992 34 15% 200 85% 234 1,250 65% 660 35% 1,910 37 3.30 8.16 Seattle, SR 520 1992 56 21% 210 79% 266 3,140 86% 498 14% 3,638 56 2.37 14 Vancouver, BC H-99 1989 27 100% 0 0% 27 1,080 100% 0 0% 1,080 40 -- 40 Sources: Developed with HOV utilization data from Tables 2-2, 2-8 (see footnotes "a" and "b"), and 2-11.

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An earlier analysis of 1989 performance of 33 out of 38 North American HOV facilities including busways then operating in freeways or separate rights-of-way found the weighted average mix of bus passengers and carpool occupants to be 63 percent bus passengers. The median mix was 41 percent bus passengers. Excluding all six facilities (not just busways) that allowed only buses, or buses and vanpools or taxis, the weighted average was 35 percent bus passengers. Of facilities that carried over 500 transit riders in the peak hour, peak direction, only one was not radial to an urban CBD, and that facility (Route 237) served California's Silicon Valley (Pratt, 1991). Analysis of the predominantly more recent information in Tables 2-22 and 2-23, covering 35 out of over 90 HOV facilities excluding busways, suggests that HOV facility modal mixes have stayed much the same except for addition of many more facilities open to carpools. The weighted aver- age mix for HOV persons in Tables 2-22 and 2-23 is 55 percent bus passengers. This is fairly con- sistent with the earlier analysis when accounting for the added facilities, all open to carpools, and exclusion of busways on separate rights-of-way from these newer tabulations. The weighted aver- age mix excluding all bus-only and bus/taxi-only facilities is 32 percent bus passengers, down marginally from the earlier 35 percent. The unweighted averages and median values, respectively, are 41 and 31 percent bus passengers for all 35 facilities and 30 and 29 percent for the facilities allowing carpools. User Distribution among Destinations Central area oriented travel, much of it in the form of bus ridership, is a major HOV facility mar- ket that favors radial facilities. Non-radial facilities must contend with dispersed travel patterns and place heavy reliance on carpool use, which itself works best with concentrated travel patterns and the parking prices common to dense development. One highly illustrative case is provided by the I-10 Katy Freeway in Houston. This freeway and its "Transitway" has a combined radial and circumferential orientation, serving not only the CBD, but also--to varying degrees--the major activity centers (MACs) of City Post Oak, Greenway Plaza, and the Texas Medical Center, along with other destinations. Destination distributions (travel markets) by mode, and mode shares by market, are provided in Table 2-24. Table 2-24 shows that 95 percent of Katy Transitway bus passengers, 65 percent of the vanpool occupants, and 56 percent of the Transitway person travel overall, are headed for downtown Houston. Especially considering that this distribution is in the presence of major alternative des- tinations, the importance of CBD orientation for HOV facilities is amply demonstrated. The MACs and the Texas Medical Center each attract 3 to 14 percent of the Transitway person travel, with negligible bus usage, leaving all other destinations throughout the metropolitan area to attract only 21 percent of the Transitway person travel. A second example is provided by Northern Virginia's I-95/I-395 HOV lanes, also a radial facility, along with the accompanying general-purpose (GP) freeway lanes and transit services. Augmented screenline survey results for the corridor are provided, broken out by both origin area and destination area, in the "Shirley Highway (I-95/I-395) HOV Lanes" case study under "More...." Within the case study, data in its Table 2-35 are employed to demonstrate major differ- ences between local person-movements in the corridor and longer trips headed for the Northern Virginia and District of Columbia regional core. For example, 90 percent of non-core person trips are in low occupancy vehicles (LOVs), while only 19 percent of longer trips from outside the Capital Beltway to the core are in LOVs. Among the remainder of these longer trips, 57 percent use the HOV lanes and 24 percent use rail transit (BMI et al., 1999b). For a more comprehensive exam- ination of I-95/I-395 HOV corridor user distribution among origins, destinations, and travel modes, refer to the case study. 2-73

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Table 2-24 Houston I-10 Katy Freeway AM Peak-Period Person Trips, Travel Market Shares by Mode and Mode Shares by Market Transitway (HOV Facility) Main Freeway Trip Destination Markets Bus Vanpool Carpool Subtotal Lanes Total Downtown 2,24 265 2,200 4,710 5,243 9,953 Destination Shares 95% 65% 39% 56% 35% 42% Mode/Lane Shares 48%/-- 6%/-- 47%/-- 100/47% --/53% --/100% City Post Oak MAC 0 52 1,135 1,187 2,996 4,183 Destination Shares 0% 13% 20% 14% 20% 18% Mode/Lane Shares 0%/-- 4%/-- 96%/-- 100/28% --/72% --/100% Greenway Plaza MAC 0 15 409 424 936 1,360 Destination Shares 0% 4% 7% 5% 6% 6% Mode/Lane Shares 0%/-- 4%/-- 96%/-- 100/31% --/69% --/100% Texas Medical Center 28 22 219 269 936 1,205 Destination Shares 1% 5% 4% 3% 6% 5% Mode/Lane Shares 10%/-- 8%/-- 81%/-- 100/22% --/78% --/100% Other 97 51 1,631 1,779 4,962 6,741 Destination Shares 4% 13% 29% 21% 33% 29% Mode/Lane Shares 5%/-- 3%/-- 92%/-- 100/26% --/74% --/100% Total 2,370 405 5,594 8,369 15,073 23,442 Destination Shares 100% 100% 100% 100% 100% 100% Mode/Lane Shares 28%/-- 5%/-- 67%/-- 100/36% --/64% --/100% Notes: Mode share percentages (before the slash) are for the Transitway (HOV facility) only. Lane share percentages (after the slash) are in comparison to the freeway subtotals/total. AM peak period is 3.5 hours long. Data collected approximately 10 miles west of downtown Houston during 2+ carpool years. Source: MacLennan (1988). User Trip Purposes and Other Characteristics The orientation of HOV travel toward commuting to major employment concentrations, especially CBDs, supports the conventional wisdom that work purpose trips are the primary travel market for HOV lanes. This assumption is supported by 2001 HOV lane user survey responses from Los Angeles County, where the HOV lane system actually has the least orientation toward the traditional central core of any in North America. Work was reported as the primary trip purpose for 90 percent of trips on the HOV lanes identified during peak periods. Non-work trip purposes were school at 4 percent and other at 6 percent. For vanpool trips, the work trip percentage was 96 percent. The survey methodology utilized, a typical mail-back survey to trip makers identified by their license plates, focused on trips as the survey universe, and not on "users" or "clients" of the HOV system (Parsons Brinckerhoff et al., 2002b). When HOV lane users were surveyed and tabulated in a manner that included all 24 hours, 7 days per week (corresponding to Los Angles County HOV lane operating hours), with occasional users given equal weight, the work travel percentage for 2-74

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people who had ever used an HOV lane became 27 percent. From this user-based rather than trip- based perspective, personal trips became the majority reason for occasional or regular HOV lane use, including 29 percent visiting family and friends, 18 percent entertainment, and 9 percent shopping (Parsons Brinckerhoff et al., 2002a). A Houston data set drawn from another trip-based self-administered survey, focusing on 6:00 AM to 9:00 AM users of HOV and GP lanes, provides 2003 trip purposes and travel characteristics for four types of Katy and Northwest Freeway users: traditional carpoolers on the HOV lanes, casual carpoolers, HOV lane express bus passengers, and travelers in the GP lanes (Burris and Winn, 2006). Selected results are provided in Table 2-25. Casual carpooling especially appears to be very much a middle-class activity. The high work purpose percentages are shown to be common, albeit with substantive variations, to all corridor travel modes in the 3-hour AM peak commute period. Sources of HOV Users HOV lanes should ideally attract new bus riders, vanpoolers, and carpoolers, rather than just diverting pre-existing HOVs from the freeway lanes or parallel roadways. Existing bus riders and HOVs are important user groups, but generating new ridesharing is critical to meeting the objec- tives of most facilities. Mode Shifts Surveys of users have been conducted on many conventional HOV facilities, often obtaining at least some information on previous mode of travel. Unfortunately, a variety of questions have been utilized, making it difficult to compare results across projects. In some cases, survey respondents were asked to identify their previous mode from a fairly comprehensive listing. In other cases, questioning has focused only on identifying previous SOV drivers. There also have been different approaches to survey sample selection. In some instances, all vehicle occupants have been sur- veyed, and in others, only carpool drivers among carpoolers have been questioned. Bus Riders and Conventional Carpoolers. Table 2-26 provides information recorded up through the mid-1990s on the prior mode of bus riders on selected HOV facilities. The table focuses on facil- ities where relatively detailed information was obtained. Table 2-27 presents similar information for carpoolers and vanpoolers. In Table 2-27, the Houston prior mode data are for carpool and van- pool drivers only, and the same may be true of the Minneapolis, Orange County, and Santa Clara County data. The Los Angeles area data for the San Bernardino Transitway and the Washington area data for Shirley Highway are for pool passengers as well as drivers. An example of the dif- ference in prior modes for drivers and passengers can be seen in Table 2-34 of the case study, "Shirley Highway (I-95/I-395) HOV Lanes." As Tables 2-26 and 2-27 demonstrate, bus riders and carpoolers who have not shifted modes, and thus apparently made only a route or lane change, compose an important constituency for many projects. Although such users do not reduce vehicular traffic through mode shifts, they do benefit from travel time and reliability improvements. In the case of bus riders who previously rode the bus, both shifting from parallel bus lines and rerouting of bus lines themselves may be involved. For HOV lane carpoolers who previously carpooled, both shifting from the GP lanes to the new HOV facility and shifting from parallel highways takes place. There is also a significant propor- tion of HOV facility bus riders and carpoolers who simply never previously made the same trip by any other mode or route. 2-75

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Table 2-25 Trip Purposes and Characteristics of AM Peak-Period Travelers on Houston's Katy and Northwest Freeway HOV and General-Purpose (GP) Lanes Characteristic Traditional HOV Slugs Transit Riders GP Lane Trips Sample Size 331 149 290 1,032 Trips per Week 9.9 9.7 9.2 9.8 Trip Purpose Commute 80% 96% 89% 85% Work (non-commute) 6% 4% 7% 9% School 7% 0% 2% 2% Other 7% 0% 1% 4% Occupation Professional/managerial 58% 68% 57% 63% Technical 10% 11% 12% 10% Sales 3% 1% 2% 7% Administrative/clerical 11% 20% 24% 8% Manufacturing 0% 0% 1% 1% Other 18% 1% 5% 11% Average Age 44.3 41.5 43.6 43.3 Percent Female 50.3% 49.3% 54.2% 39.1% Household Size 3.32 3.01 3.06 3.02 Number of Vehicles 2.39 2.22 2.19 2.42 Income Less than $25,000 1% 1% 4% 2% $25,000 to $34,999 1% 1% 8% 5% $35,000 to $49,999 14% 14% 12% 10% $50,000 to $74,999 28% 28% 24% 20% $75,000 to $99,999 25% 25% 20% 22% $100,000 to $199,999 30% 30% 28% 32% $200,000 or more 2% 2% 3% 9% Notes: The traditional HOV sample was limited to users of the HOV lanes. The casual carpooler sample was restricted to passengers (slugs) casual carpooling four-or-more days a week. The slug and transit rider samples may be presumed to represent HOV lane users only. Source: Burris and Winn (2006), average age estimated from range percentages by Handbook authors. Both tables show that many HOV facilities have been successful in inducing individuals who for- merly drove alone to take the bus or carpool. For example, between a quarter and over a half of the bus riders in the projects highlighted in Table 2-26 previously drove alone. The carpoolers sur- veyed on the HOV lanes in Table 2-27 have an even higher rate of reporting "drove alone" as the previous mode, ranging from over a third to over a half. Additional information on the projects listed in Tables 2-26 and 2-27, and other projects as well, is discussed next. 2-76

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Table 2-26 Prior Mode of HOV Lane Bus Riders Previous Mode (percent) a Drove Car- Van- Did Not Facility (Year of Survey) b Alone pooled pooled Bus Make Trip Other Dallas I-30 R. L. Thornton (1995) 24% 4% 0% 57% 9% 6% Houston I-10W Katy (1995) 46 8 8 3 30 5 US 290 Northwest (1995) 43 12 8 3 25 9 I-45 North (1990) 39 9 8 15 28 1 I-45 Gulf (1989) 38 8 6 30 18 0 Los Angeles San Bernardino Transitway 50 24 -- 10 12 4 (1974 Bus-Only Operation c ) San Bernardino Transitway 55 7 -- 8 21 9 (1977 Mixed-Mode new transitway bus riders only d ) Washington, DC Auto Auto Driver Passenger I-395 Shirley Highway (1974) 41% 12% -- 38 9e --e Notes: -- - Not explicitly surveyed. a Based on surveys of HOV lane users. b Year in parenthesis indicates the year the survey was conducted. c After 12 months of bus-only operation. d After 6 months of mixed-mode Transitway operation, with new bus riders defined as riding 6 months or less. e Did not make trip and other combined. For additional observations, see Chapter 4, "Busways, BRT and Express Bus," under "Related Information and Impacts" "Sources of BRT/Express Bus Ridership." Sources: Bullard (1991), Crain & Associates (1978), Pratt, Pedersen and Mather (1977), Turnbull, Turner and Lindquist (1995). Bus riders and carpoolers on the Shirley Highway HOV lanes in Northern Virginia, now I-395, were surveyed as part of the evaluation of the initial demonstration in the 1970s. A 4 vehicle occupancy requirement was in effect at the time. Analysis of the survey results indicates that some 41 percent of the bus riders and 39 percent of the carpoolers formerly drove, either alone or as a carpool driver. The prior drove-alone percentages can be estimated at roughly 35 percent of bus riders and 25 percent of carpoolers. It can also be demonstrated that the proportions of prior auto passengers among bus passengers and of prior bus riders among carpoolers, while significant, were each less than the previous proportional usage of these modes in the travel corridor (McQueen et al., 1975; Pratt, Pedersen and Mather, 1977). (See the "Shirley Highway [I-95/I-395] HOV Lanes" case study for more detailed prior mode data.) Surveys taken on the San Bernardino Transitway of Los Angeles in 1974, and then in 1977 after carpools were allowed, indicate the facility played a major role in new bus rider attraction and new carpool formation. Among 1974 survey respondents, 50 percent of the bus passengers had previously driven alone. Of carpool drivers and passengers surveyed at the central area exit 2-77

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Table 2-27 Prior Mode of HOV Lane Carpoolers and Vanpoolers Previous Mode (percent) a Drove Car- Van- Did Not Facility (Year of Survey) b Alone pooled pooled Bus Make Trip Other Houston c I-10W Katy (1990) 57% 27% 3% 9% 4% -- I-45 North (1990) 42 39 3 15 1 -- US 290 Northwest (1990) 53 34 1 8 4 -- I-45 Gulf (1989) 40 44 7 4 4 -- Los Angeles San Bernardino Transitway (1977) After 6 months mixed-mode 46 23 -- 21 9 1 After 13 months mixed-mode d 39 12 -- 32 16 -- Minneapolis I-394 (1987)e 38 54 -- 8 8 Orange County SR 55 (1987) 56 33f -- -- 11 -- Santa Clara County SR 237 (1988) 56 12 1 2 22 7 Washington, DC Auto Auto Driver Passenger I-395 Shirley Highway (1974) 39% 30% -- 25 6g --g Notes: -- - Not explicitly surveyed. a Based on surveys of HOV lane users. b Year in parenthesis indicates the year the survey was conducted. c Houston data are for carpool and vanpool drivers. Minneapolis, Orange County, and Santa Clara County data may also represent drivers only. d Carpools using central area exit only. e Interim HOV lane in operation. f Previously carpooled on SR 55, 28%; previously carpooled on another route, 5%. g Did not make trip and other combined. Sources: Bullard (1991); Communication Technologies (1989); Crain & Associates (1978); Pratt, Pedersen, and Mather (1977); SRF, Inc. (1987); Wesemann, Duve and Roach (1988). toward the end of 1977, 39 percent drove alone before formation of their carpool, as shown in Table 2-27. That most of these carpool formations were in response to HOV lane availability is illustrated by the companion finding that 36 percent drove alone before the carpool appeared on the transitway. Other prior mode percentages are given in Tables 2-26 and 2-27 (Crain & Associates, 1978). Carpoolers using Route 55 in Orange County, California, were surveyed in 1985 and 1987. Carpool volumes increased from approximately 332 in 1985--prior to the opening of Route 55 HOV lanes--to 653 in 1987, after 18 months of HOV lanes operation. The 1987 survey results indicate that 56 percent of the carpoolers previously drove alone, while 28 percent were from existing carpools, and 11 per- cent were new trips in the corridor (Wesemann, Duve and Roach, 1988). In the first year of operation 2-78

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for the I-15 HOV lanes opened in Salt Lake City and suburbs in 2001, affected freeway corridor seg- ments exhibited an 18 percent increase in AVO on average. AVO on other area freeway segments held steady (Martin et al., 2004). A survey of carpoolers using the New York area Long Island Expressway HOV lane was con- ducted in 1997. Specific prior travel mode questions were not included, but changes in travel behavior as a result of the HOV lane were explored, with the results shown in Table 2-28. Some 15 percent of respondents indicated they formed a carpool as a result of the HOV lane, while 12 percent reported sharing a ride occasionally to use the HOV lane, and 2 percent increased the size of their carpool. A change in travel route to take advantage of the HOV lane was reported by 35 percent, while 54 percent reported making no change in travel patterns (Urbitran and Hayden- Wegman, 1997). Periodic surveys of carpool drivers and bus passengers have been conducted on Houston's HOV lanes. Results show the lanes to be attracting both new carpoolers and new bus riders. Between 36 and 46 percent of current carpool drivers on four of the Houston HOV lanes indicated they previ- ously drove alone, while 38 to 46 percent of current bus riders formerly drove alone (Bullard, 1991; Turnbull, Turner and Lindquist, 1995). Surveys taken after a number of years of operation reflect more the ongoing process of travel changes under stable conditions than the shifts that occur upon opening of a facility. Even surveys taken soon after a new facility opening reflect in part normal changes in travel choices. Surveys focused only on carpool and bus passengers can identify shifts from drive-alone to ridesharing, but not the converse, hence they likely overstate the reduction in drive-alone travel. Casual Carpoolers. Prior or alternative mode information from San Francisco on casual carpool- ers suggests a very different pattern for that niche carpooler category as compared to conventional carpoolers. Table 2-29 presents prior mode information for casual carpooling across the San Francisco-Oakland Bay Bridge at two points in time during sharp growth in casual carpooling and then for a more recent year with somewhat more stable conditions. Casual carpool participant totals during the two initial surveys were about 3,000 in 1985 and 5,000 in 1987. The total for 1998 is thought to have been on the order of 8,000 participants. Driver and rider commute modes before casual carpooling are listed separately, and for 1998, individuals who do both are also identified Table 2-28 Travel Pattern Changes of Long Island Expressway HOV Lane Users Travel Pattern Change Number Percentage Changed routes to use HOV lane 288 35% Now share ride occasionally to use HOV lane 101 12% Joined/formed carpool to travel to and from work 126 15% Increased size of carpool 15 2% Other 31 4% No change in travel patterns 448 54% Notes: Survey question was "Have the HOV lanes caused you to change your travel patterns in any way?" Percentages based on total number of respondents (831). Multiple responses allowed. Source: Urbitran and Hayden-Wegman (1997). 2-79

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Table 2-29 San Francisco East Bay Commute Mode Before Casual Carpooling 1985 Survey 1987 Survey 1998 Survey a Prior Mode Drivers Riders Drivers Riders Drivers Riders Combo b Drove alone 44% 6% 49% 5% 40% 9% 20% Drove with one another 12 3 4 2 7 3 3 BART (HRT/Metro) 10 30 25 37 25 52 37 AC Transit (bus) 16 55 8 39 8 22 13 Formal carpool 18 5 4 4 3 2 2 Always casual carpooled n/a n/a 10 12 5 3 3 Lived elsewhere n/a n/a n/a n/a 8 6 12 Other n/a n/a n/a n/a 4 4 9 a Note: Inclusion of the "lived elsewhere" and "other" options in the 1998 survey deflates the 1998 prior mode percentages relative to the earlier surveys. For example, the 1985 and 1998 "drove alone" prior mode proportions for drivers are probably in fact nearly identical. b Casual carpoolers who are sometimes drivers and sometimes riders. Source: Beroldo (1990), Rides for Bay Area Commuters (1999). separately. Of drivers, 51 to 56 percent previously used transit or some other ridesharing mode, while 90 to 95 percent of riders previously used transit or another ridesharing arrangement.5 The higher mode shifting from BART heavy rail transit (HRT) in the second survey was traced to a BART fare increase. There was also a BART fare increase prior to the 1998 survey, along with a doubling of Bay Bridge tolls and an HOV lane extension northward (Beroldo, 1990; Rides for Bay Area Commuters, 1999). This makeup of prior or alternative modes suggests that casual carpooling may not be a significant factor in vehicular trip reduction. In the San Francisco Bay Area, estimates produced with 3 sepa- rate sets of assumptions and utilizing the 1985 and 1987 data in Table 2-29 along with other infor- mation led to a conclusion that casual carpooling may actually increase traffic slightly (Beroldo, 1990). A more recent evaluation based on both prior mode and alternative mode survey questions produced estimates that without casual carpooling there would be on the order of 300 to 600 fewer cars on the road. Not addressed quantitatively was the extent to which casual carpooling might make the broad universe of ridesharing--including transit riding--more attractive and flexible to the user (Rides for Bay Area Commuters, 1999). Route Shifts As already noted, HOV facilities may impact choice of route within a corridor or area. For exam- ple, as shown in Table 2-28, 35 percent of carpoolers surveyed on the Long Island Expressway in 1996 indicated they had changed their travel route to use the HOV lane. Others changed modes as discussed above. On the other hand, 54 percent reported no change in their travel patterns in response to the HOV lane (Urbitran and Hayden-Wegman, 1997). 5In computing these ranges, 1998 survey results have been adjusted by the Handbook authors for rough com- parability to earlier survey findings (see footnote "a" in Table 2-29). 2-80

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The periodic surveys of HOV lane users in Houston, and one survey in Dallas, also point out the influence of the HOV system on changes in route choice. For example, between 9 and 19 percent of the carpoolers on the Katy, Northwest, and East R. L. Thornton HOV lanes responding to a 1995 sur- vey indicated they had previously used a parallel street or highway (Turnbull, Turner and Lindquist, 1995). Further, the survey results found that some 2 carpools changed from using the Katy HOV lane to the Northwest HOV lane when the AM peak-hour occupancy requirement was increased to 3 on the Katy. Fourteen percent of the carpools on the Northwest HOV lane responding to a 1989 survey indicated they were previous Katy HOV lane users (Christiansen and Morris, 1990). A 2001 survey of HOV lane users in Los Angeles County provides detail on both route and mode shifts under conditions where 15 of 16 HOV facility segments surveyed had been in service an average of 3 years. The other segment had been in service for decades. Results are provided in Table 2-30. It may be inferred from the results that 68 percent of surveyed carpoolers previously used the GP lanes of the same freeway, a little over 3/4 driving alone, and the rest in carpools or vanpools. Some 20 percent traveled on a different street or freeway, not quite half driving alone. Looked at another way, roughly 1 in 7 of carpoolers who previously drove alone shifted routes, while about 2 in 5 of carpoolers who were carpooling or vanpooling before shifted routes (Parsons Brinckerhoff et al., 2002a). The multiple response nature of the survey and questions about where the "Traveled in a different area" response fits in cloud possible conclusions. Nevertheless, there is certainly a propensity for carpoolers to shift routes to gain HOV lane advantages. Time to Establish Ridership and Use Available data on operating HOV lanes indicates that use and ridership levels can be expected to grow over the first months and years of operation. In some cases it appears that HOV lanes may reach a level of maturity where little or no growth is experienced. Any such leveling-off often takes longer to come about than the 2 years, or sometimes 3, typical for new transit facilities and services. This may, in some cases, be partially attributable to delayed or staged response by transit operators in rerouting and expanding bus services to take full advantage of the new facilities. In any case, there is typically a recursive process of transit ridership increases, followed by further development of transit service Table 2-30 Prior Means of Travel for Los Angeles County Freeway HOV Lane Users Prior Means of Making Trip Percentage Traveled in a different area 19% Drove alone in general purpose lanes 52% Carpool or vanpool in general purpose lanes 16% Drove alone on parallel street or freeway 9% Carpool or vanpool in different freeway carpool lane 6% Carpool or vanpool on different freeway without carpool lane 5% Other 1% Notes: Survey question was "Prior to using carpool lanes, how did you make this trip?" Multiple responses were allowed. Number of respondents was 1,356. Source: Parsons Brinckerhoff et al. (2002a). 2-81

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levels, and change in the regulatory and political environment. The need for transit services, park- and-ride lots, rideshare programs, marketing and public information programs, enforcement, and other activities supporting enhanced HOV use was identified in the planning process. A num- ber of key elements were not followed through on, however, especially on I-287. Only one new 50-space park-and-ride lot was provided in the I-80 corridor. No park-and-ride facilities and no bus services were implemented along I-287. Only one of the recommended improvements to the I-80/ I-287 interchange was completed. The direct HOV connection between I-80 eastbound and I-287 southbound, which would have provided HOVs with significant travel time savings, was not implemented. While commuters headed into and out of the New York City metropolis on I-80 were logical car- pool and bus passenger candidates, the diversity of trip origins and destinations associated with the low density suburban developments in both corridors made sharing a ride or taking a bus dif- ficult for most potential HOV lane users. Promoting HOV use in the absence of a major employ- ment concentration is hard, and the I-287 HOV lane in particular suffered as a consequence. Major changes in the regulatory or authorizing environment over the course of the projects did not help. At the outset, federal requirements contained in the 1990 Clean Air Act Amendments and the 1991 ISTEA, as well as New Jersey Traffic Congestion and Air Pollution Control Act and the activities of the New Jersey Transportation Executive Council, mandated or supported HOV facilities, TDM strategies, and other measures to reduce VMT and emissions. By the time the I-80 and I-287 HOV lanes were in operation, Congress had changed the mandatory Employee Trip Reduction Program to a voluntary effort and a similar change was made in the state program. As a result, employers in the two corridors backed away from planned transit, ridesharing, and other programs predi- cated on a mandatory Employee Trip Reduction Program. Thus many incentives for mode shifts from driving alone to carpooling, vanpooling, or riding a bus that had been assumed in making the projections for HOV use of the I-287 lanes were gone. In addition, a change in the political land- scape during the course of implementing the HOV lanes was reflected in modifications of policies and priorities that affected implementation decision-making (Turnbull and DeJohn, 2000). HOT Lane Situations There have been no terminations of HOT lane projects as yet. The initial demonstration transitions from HOV lanes to HOT lanes described in Chapter 14, "Road Value Pricing," all involved allowing onto the HOV facility a new user group--toll-paying lower-occupancy vehicles--without any further restric- tions on any existing user groups. Implementation went relatively smoothly. The May 2005 imple- mentation of I-394 HOT lanes in Minneapolis raised the old take-a-lane bugaboo again, however, in a limited way. A point of conflict on the Citizen Advisory Committee engaged throughout planning and design was charging a toll, generally 25, in the off-peak hours/off-peak direction on concurrent-flow HOV lanes that had previously been open to all vehicles except in the peak hours/direction. Advisory Committee membership included several legislators instrumental in passing Minnesota's HOT lane legislation (Howard, MacDonald, and Hammond, 2005; TOLLROADSnews, 2005). The I-394 HOT lanes were implemented with 24-hour tolls for single-occupant vehicles using not only the barrier-separated section but also the with-flow lanes in question. Congestion occurred in the outbound off-peak direction at about the project's mid-point. Although the problem would apparently have been susceptible to mitigation with a new auxiliary lane, public outcry led the Minnesota Senate to quickly pass a resolution calling for the off-peak tolls to be rescinded (TOLLROADSnews, 2005). This has been done. The tolls now apply to the concurrent flow lanes in the peak period, peak direction only. Otherwise, I-394 HOT lanes implementation appears to have gone well (refer to "More . . ." in the "Minneapolis I-394 HOV Facilities" case study for addi- tional information). 2-87

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Impacts on AVOs, Traffic Volumes, and Vehicle Miles of Travel By encouraging SOV drivers to change to a high occupancy travel mode, HOV lanes may help reduce both traffic volumes in the GP lanes and vehicle miles of travel (VMT) overall. Most HOV lanes are operating in heavily congested travel corridors, however, which continue to experience increases in travel demand. As a result, although traffic volumes and VMT may decline slightly when an HOV lane is opened, and be kept lower than they might otherwise be, HOV facilities do not appear to be able to counter long-term growth trends in travel demand and VMT. A more realistic expectation is that HOV lanes may help reduce the growth in VMT by achieving higher vehicle occupancies. Table 2-31 highlights AM peak-hour changes in freeway auto, vanpool and bus average vehicle occupancy (AVO) before and after HOV facility implementation. The before AVO is for the freeway GP lanes and the after AVO is for the combined HOV and GP lanes. The change, over periods of time that vary from 1 to 20 years, ranged from a 2 percent decline in AVO to a 36 percent gain. The 22 projects averaged a 9 percent gain in AVO over the measured periods. A quite different data set from the 1970s indicates a fairly similar outcome. This earlier data set provides auto occupancies (auto, carpool, and vanpool AVO) before and after either newly intro- ducing an HOV lane open to carpools, or changing bus lane eligibility requirements to admit car- pools. Australia, California, Hawaii, Florida, Massachusetts, Oregon, and Virginia are represented in the 12 projects. Measurements were made over time periods all less than a decade and some as short as a few months. Results ranged from a 2 percent to a 19 percent gain in auto occupancy, aver- aging an 8 percent gain (Pratt and Copple, 1981). Note, however, that the all-important bus rider market is missing from this earlier analysis, and some effects of 1970s fuel crises may be reflected in the data set. It must also be recognized that both these and the Table 2-31 results are for the freeway or bridge involved, and except for two water crossings in the 1970s data set, there may have been some diver- sion of carpoolers from parallel facilities, inflating the AVO increases. The two known analyses made corridor-wide, thereby addressing this concern, were presented in connection with Table 2-5 under "Traveler Response by Type of HOV Application"--"Response to Exclusive Freeway HOV Lanes." A comprehensive assessment of the VMT impacts of HOV projects, as well as impacts associated with air quality and environmental factors, should consider not only the facility itself, and the cor- ridor it is located in, but also other elements of the trip. These may include the travel associated with picking up and dropping off carpool and vanpool members, accessing the HOV lane, and entering and exiting special parking facilities. The VMT associated with new or expanded bus ser- vice should also be included in the analysis. No existing study has incorporated all of these factors into examining the impact of HOV facilities on VMT and other related elements. An old rule of thumb that took account of auto access and carpool circuitry was that 35 to 45 per- cent of gross VMT reduction offered by HOV facility strategies is counterbalanced by VMT incurred in these activities (Wagner, 1980). Analysis of San Bernardino busway VMT savings (bus riders only) indicated that 41 percent of the gross VMT reduction was counterbalanced by access requirements plus another 16 percent by use of autos left at home (Pratt and Copple, 1981). The casual carpooling component of HOV facility use, where it exists, is a special case. There is a lack of consensus regarding its net impacts on VMT and the use of alternative modes (see "Sources of HOV Users"--"Mode Shifts"--"Casual Carpoolers" above). In a development closely aligned to issues of traffic volume and VMT, a researcher at the University of California reports use of Caltrans Performance Monitoring System sensor data to 2-88

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Table 2-31 Examples of Changes in AM Peak-Hour Freeway Average Vehicle Occupancy (AVO) -- Before and After HOV Facility Facility Before Date a After Date a Before AVO b,c After AVO b,d Change Dallas, Texas East R. L. Thornton 1991 1996 1.35 1.33 -1% Houston, Texas I-45N (North) 1978 1996 1.28 1.41 +10% I-45S (Gulf) 1988 1996 1.29 1.26 -2% I-10W (Katy) 1983 1996 1.26 1.52 +21% US 290 (Northwest) 1987 1996 1.14 1.36 +19% US 59S (Southwest) 1992 1996 1.16 1.29 +11% Los Angeles, California e I-10 San Bernardino 1972 ca. 2000 1.29 1.55 +20% I-110 Harbor (outer) ca. 1995 ca. 2000 1.21 1.27 +5% I-210 Foothill ca. 1992 ca. 2000 1.19 1.24 +4% I-405 San Diego (No.) ca. 1995 ca. 2000 1.20 1.22 +2% I-405 San Diego (So.) ca. 1997 ca. 2000 1.10 1.18 +7% CA 14 Antelope Valley ca. 1997 ca. 2000 1.17 1.32 +13% CA 57 Orange ca. 1996 ca. 2000 1.12 1.21 +8% CA 60 Pomona (outer) ca. 1998 ca. 2000 1.09 1.28 +17% CA 91 R. B./Artesia ca. 1993 ca. 2000 1.17 1.21 +3% CA 118 Ronald Reagan ca. 1996 ca. 2000 1.15 1.18 +3% CA 134 Ventura ca. 1995 ca. 2000 1.12 1.19 +6% CA 170 Hollywood ca. 1995 ca. 2000 1.23 1.23 0% CA 605 San Gabriel River ca. 1997 ca. 2000 1.09 1.18 +8% Orange Co., California SR 55, Orange County 1985 1992 1.18 1.28 +8% Minneapolis, Minnesota I-394 1984 1998 1.42 1.51 +6% Seattle I-5 North 1982 1992 1.24 1.69 +36% a Notes: Where possible, AVOs are from "before and after" analysis sources, thus the dates and data may not match other tabulations in this chapter. b Includes automobiles, vanpools, and buses. c Before data are for freeway only. d After data are for freeway and HOV facility combined. e For Los Angeles County facilities opened in the 1990s, the "Before Date" is assumed to be 2 years prior to the reported first full year of operation, and the "Before AVO" is calculated from the reported percent change and "After AVO." Sources: Minnesota DOT (1998a), Stockton et al. (1997), Turnbull (1992b), Parsons Brinckerhoff et al. (2002a). 2-89

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conclude that maximum freeway capacity is achieved at 60 miles per hour flow rates rather than 45 to 50 mph. In a related conclusion, evidence is found that the limitations on passing within single-lane HOV facilities tend to hold peak traffic speeds below 50 mph, and that the typical HOV lane decreases speeds in the GP lanes. These are conditions that acting together would--if 60 mph is optimum--tend to reduce capacity and diminish traffic level-of-service and environmental ben- efits obtained from HOV-induced traffic mitigation. Variance in auto occupancy estimates pre- vented estimation of whether HOV facilities of interest to the study actually increased or reduced total congestion delay (Varaia, 2005). The issues thus raised about HOV lane utility appear to be of least concern for facilities with sub- stantial bus volumes or a 3 or greater occupancy requirement. The high AVOs on such facilities should, assuming them to be well used, render largely inconsequential the speed-related person- carrying capacity reduction inferred from the research findings. The concerns are also largely inap- plicable to multi-lane HOV facilities. Should the flow analyses of the research be borne out, the findings would suggest certain advantages to consider for managed lane strategies applied to mul- tiple lanes or for metered freeways with HOV bypass lanes and exclusive HOV ramps but no single-lane full-facility HOV provisions. An example of the latter is offered by the 1970s installa- tion on I-35W in Minneapolis (see "Traveler Response by Type of HOV Application"--"Response to Ramp Meter Bypasses and HOV Access Treatment"--"Minneapolis-St. Paul"). The Texas Transportation Institute's Annual Mobility Report for 2003 provides more of a top-down, macro-analysis of HOV lane congestion-reduction impacts. Analysis of 8 to 10 cities suggests that the reduction in traffic delay afforded by HOV lane systems is twice that of signal coordination efforts, a quarter of what ramp metering provides, not quite one-fifth the reduction afforded by freeway inci- dent management, and one-sixtieth of the beneficial effect of providing public transportation over- all (Urban Transportation Monitor, 2003). Public transportation is, of course, a function enhanced by most HOV lane installations. Impacts on Energy, Air Quality, and Environmental Factors The research conducted for this Handbook and other recent projects (Turnbull and Capelle, 1998) has identified a lack of in-depth information on the air quality, energy, and other related environ- mental impacts of HOV facilities. Most of the studies conducted to date focus on the use of com- puter simulation models either to estimate the impacts of an HOV facility compared to other alternatives, or to estimate the impacts of an operating HOV project based on the number of peo- ple in buses, vanpools, and carpools. These types of analyses generally, but not always, indicate that HOV facilities have positive impacts on air quality, energy, and the environment. On the other hand, some groups have suggested that, because of induced travel, the construction of HOV lanes may actually have negative impacts on air quality by increasing VMT and vehicle emissions. Some individuals and groups contend that only converting a GP lane to an HOV lane will have positive influ- ences on air quality levels, or that other transit alternatives are more environmentally friendly (Leman, Schiller, and Pauly, 1994; Johnston and Ceerla, 1996; Sucher, 1997). In the discussion that follows, avail- able analyses indicating positive impacts of HOV lanes on air quality, energy, and the environment are described first, followed by studies questioning the environmental benefits of HOV facilities. Positive Computer Simulation Model Results The analysis of the air quality and energy impacts of the Houston HOV lanes provides one exam- ple of the use of computer simulation models to estimate the impact of different transportation 2-90

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improvement alternatives (Stockton et al., 1997). The approach used in this analysis was based on the realization that implementing an HOV lane does not necessarily reduce vehicular volumes on the freeway, but rather allows more persons to use the total facility without increasing congestion in the freeway GP lanes. As a result, the HOV lane traffic may increase the VMT compared to the condition before the opening of the facility but may reduce the growth in VMT. Thus, an increase in total VMT may result, which may also increase the amount of energy consumed and pollutants emitted. To address this issue, the analysis in Houston focused on asking the question, "What is the most effective means of serving the travel demand that is expected to occur and what are the air qual- ity and energy impacts of the different alternatives?" The analysis used the freeway simulation computer model FREQ and examined the following three alternatives for the Katy Freeway. Do Nothing--This alternative had three GP traffic lanes in each direction and no HOV facility in the corridor. It represented the conditions that existed prior to implementation of the HOV lane. Add a GP Traffic Lane--This alternative provided a total of four GP traffic lanes in each direc- tion with no HOV lanes. Add an HOV Lane--This alternative had three GP traffic lanes in each direction and a reversible HOV lane. This alternative represents the scenario that was implemented. Using the FREQ model, the operation on both the freeway GP lanes and the HOV lane was simu- lated. The 1991 demand, expressed in person miles, was held constant across the alternatives, and the AVO was adjusted between alternatives as necessary to reflect the observed impacts of the HOV facility on vehicle occupancy. The alternative with the HOV lane provided the greatest air quality and energy benefits. The HOV lane alternative generated the lowest levels of emissions for hydro- carbons and carbon monoxide, and was only slightly higher than the 3 GP lane/no HOV lane alter- native in nitrogen oxide. The HOV lane option also resulted in the lowest levels of gasoline consumption among the alternatives. The analysis also indicated that since increases in demand are expected to continue, the HOV lane alternative may provide even greater benefits because it pro- vides capacity to serve additional growth while the other alternatives do not (Stockton et al., 1997). Positive Analysis Results Starting with Empirical Data The initial evaluation of the Shirley Highway Express-Bus-on-Freeway Demonstration included an examination of the environmental impacts of the project. The final evaluation report indicated that the project had positive environmental impacts in the corridor. This analysis was based on an estimate of the number of automobiles that would have used the freeway if motorists were not diverted to the express bus services or carpools using the HOV lanes. The number of motorists who changed from driving alone to using the bus or carpooling was estimated based on surveys of the two groups. This provided an estimate of the reduction in peak-period automobile volumes, which was used to calculate changes in automobile generated air pollution and gasoline consumption. The analysis indicated that, in 1974, the Shirley Highway HOV lanes had achieved a reduction of approximately 21 percent in carbon monoxide, hydrocarbon, and nitrogen oxide emissions, and saved approximately 17,200 gallons of gasoline daily, or about a 23 percent reduction in the level of consumption without the facility (McQueen et al., 1975). The evaluation covering the first 5 years of operation on the San Bernardino Freeway Busway also examined the air quality and energy impacts of the facility. An approach similar to the one used 2-91

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by the Shirley Highway Express-Bus-on-Freeway Demonstration evaluation was used. Reductions in vehicles on the freeway and VMT resulting from the operation of the HOV facility were esti- mated based on surveys of bus riders and carpoolers. The analysis identified a 10 to 20 percent reduction in air pollutant emissions over the peak period in the peak direction of travel resulting from the HOV lane improvement. Energy savings were estimated at 7 to 10 percent during the same time period (Crain & Associates, 1978). It goes without saying that both the Shirley Highway and San Bernardino Transitway calculations were done in the context of 1970s vehicle emissions and energy consumption characteristics. The HOV lanes evaluations recently carried out in Los Angeles County offer more up-to-date but less comprehensive estimates. They focused on simple comparison of computed vehicle emissions for the HOV lanes relative to the parallel GP lanes, and for the freeway study segments with HOV lanes relative to 2 control segments without HOV lanes. In most cases, HOV lane emission rates were roughly half the rates for parallel GP lanes, despite the typically higher person volumes car- ried by the HOV lanes. In only 3 of 50 sub-segments and AM or PM peak hours analyzed were HOV lane emission rates higher than GP lane rates. On the other hand, a majority of the AM or PM peak freeway-with-HOV analysis sub-segments had higher calculated emissions than the 2 con- trol segments, which happened to have operating speeds close to the optimum for minimum emis- sions. It was acknowledged that data limitations had prevented a truly comprehensive assessment (Parsons Brinckerhoff et al., 2002a). Negative Evaluation Results The Minnesota Department of Transportation (MnDOT), in lieu of temporarily converting the two Minneapolis HOV lanes to GP lanes as a test, commissioned an evaluation of the likely effect. An assumption made was that, wherever feasible, shoulder bus lanes would be provided in compen- sation. Involved were the I-35W concurrent flow HOV lanes and the concurrent flow and exclusive/reversible HOV lanes on I-394. The evaluation produced estimates by employing the regional 4-step modeling process for demand forecasting and the U.S. DOT's Intelligent Transportation System (ITS) Deployment Analysis System (IDAS), with adjustments to reflect local conditions along with Mobile5A emission rates, for benefit quantification. The demand modeling along with market research indicated that loss of the reliability, travel time savings, and cost sav- ings offered by the HOV lanes would cause some 13 to 25 percent of I-35W and I-394 carpoolers and bus riders to shift to driving alone. VMT was projected to increase. Nevertheless, it was determined that there was sufficient excess vehicular capacity on the Minneapolis HOV lanes that opening them to general-purpose traffic would improve overall traf- fic conditions. It was estimated that this circumstance would result in positive emissions benefits valued at $1.5 million for the year 2000 despite the projected VMT increase. A slight rise in nitro- gen oxide emissions was projected to be more than compensated for by reductions in carbon monoxide and hydrocarbons. Improved speeds were estimated to reduce fuel consumption by 4,000 gallons per day, producing an additional $1.5 million annual benefit. These positive impact estimates for HOV lane decommissioning are, of course, negative findings with respect to the Minneapolis HOV system (Cambridge Systematics and URS, 2002). Other studies indicating that HOV lanes may have a negative impact on air quality and other environmental factors focus on the following points: First, if an added HOV lane results in remov- ing vehicles from the GP lanes, the speeds in those lanes will increase, upping nitrogen oxide emissions. Second, as the available capacity in the GP lanes is filled by new SOVs, overall VMT will rise, increasing in turn the energy consumed and pollutants emitted. Further, some environ- mental groups have suggested that HOV facilities are just a way to construct additional lanes that 2-92

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will ultimately be converted to GP lanes (Leman, Schiller and Pauly, 1994; Johnston and Ceerla, 1996; Sucher, 1997). These conflicting analyses indicate the complexity of assessing the air quality and environmental impacts of HOV lanes. The need for additional research in this area has been identified in other recent projects (Turnbull and Capelle, 1998; Transportation Research Board, 1995). Suggested research would examine the vehicle occupancy and congestion trade-offs associated with HOV lanes, modeling the air quality impacts of HOV facilities and HOV networks, examining the impact of HOV lanes on traffic operations and air quality, assessing the effect of lane conversion projects compared to new HOV lanes, and analyzing the impact of HOV facilities on noise, water quality, and other environmental issues (Turnbull and Capelle, 1998). To fully address the issues posed, such research would need to be conducted on a corridor-wide basis, and with consideration of land use development and induced travel effects among other travel demand factors. Costs, Revenues, and Benefits Effects on Transit Services By increasing bus operating speeds, improving service reliability, and providing an operating envi- ronment with fewer traffic incidents, HOV facilities may improve the efficiency of bus operations. Some combination of bus transit operating cost savings, enhanced vehicle productivity, improved on- time performance, and lower vehicle accident rates may reasonably be anticipated. However, these presumed impacts have not been examined extensively. The best available such information is from studies of the Shirley Highway HOV lanes and the Houston HOV lanes. Comparable information on busways is found in Chapter 4, "Busways, BRT and Express Bus." The Minneapolis modeling effort described above provides additional perspective, and both it and the contemporary Los Angeles County HOV lanes evaluations address overall benefits or disbenefits to all parties of HOV lanes. The before-and-after evaluation of the Shirley Highway Express-Bus-on-Freeway Demonstration Project, conducted in the early 1970s, attempted to examine effects of opening the HOV lanes on bus on-time performance, bus service productivity, and the financial status of the operator. Schedule adherence checks at the first downtown stop showed bus on-time performance to have improved substantially, a result attributed to increased bus operating speeds and more reliable travel times. (See also "Trip Time Reliability" under "Underlying Traveler Response Factors.") The evaluation was unable to measure the direct impact of the HOV lanes on bus operator pro- ductivity, because of a lack of route-level operating statistics. However, an estimate was made of the bus requirements if the buses were operating at the slower speeds of the GP lanes. It was esti- mated that 17 additional buses would be needed, equivalent to a monthly capital and operating cost of $26,600 in 1973 dollars. The analysis also indicated that peak-period bus operating costs had been reduced slightly with the opening of the HOV facility (McQueen et al., 1975). Analysis of the impact of Houston's HOV lanes on bus service enhancements and operating costs showed AM peak-hour bus operating speeds on the freeway to have almost doubled, on average, increasing from 26 mph to 54 mph. This speed increase led to significant reductions in bus sched- ule times. For example, scheduled bus travel times from the Addicks Park-and-Ride lot on the Katy Freeway to downtown dropped from 45 to 24 minutes with HOV lane introduction, while travel times from the Northwest State Park-and-Ride lot on the Northwest Freeway were reduced from 50 to 30 minutes (Turnbull, 1992b; Stockton et al., 1997). 2-93

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The impacts of the opening of a direct access ramp from the Northwest Station Park-and-Ride lot to the Northwest (US 290) HOV lane, the reopening of an almost 4-mile segment of the North (I-45N) HOV lane closed due to construction, and the 1-1/2 mile eastern extension to the Katy (I-10W) HOV lanes were also examined. It was estimated that the three HOV elements in total reduced the revenue bus hours needed to provide service by 31,000 hours annually. At an average fully allocated cost of $152 per revenue bus hour, the HOV lanes reduced METRO's 1992 operat- ing costs by approximately $4.8 million (Stockton et al., 1997).6 The previously described MnDOT model simulation of converting the two Minneapolis HOV lanes to GP lanes provided an estimate that 15 additional buses would be required to maintain frequen- cies in the face of slowed bus travel, even with the assumed provision of shoulder bus lanes. The one- time capital cost of these buses was calculated to be $7.8 million in 2001 dollars. Bus-only shoulder capital costs were estimated at $2.9 million. Recurring costs for operating and maintaining the addi- tional buses were projected to be $3.1 million annually (Cambridge Systematics and URS, 2002). Transit cost and revenue issues related to the HOV facility niche mode of casual carpooling were touched upon in the "Underlying Traveler Response Factors"--"Carpool Composition and Longevity"--"Casual Carpooling" subsection. Whatever the cost savings or revenue loss to tran- sit operators, casual carpooling is obviously a negligible-cost benefit to those who do it. Overall Effects on Benefits Despite the estimated negative impact on transit costs noted above for changing the Minneapolis HOV lanes back to GP lanes, the MnDOT study in question obtained a positive cost-benefit ratio overall for such reversion. The cost-benefit ratio was estimated to be 2.1 if there was no federal HOV lane contribution buy-back penalty, and 1.6 otherwise, a negative finding for HOV lanes. The study took note, however, that the Minneapolis HOV lanes are an integral part of a multifaceted region-wide program of "multimodal transportation options, travel time advantages to transit, and ridesharing incentives" and recommended against opening them to all traffic. It recommend that there be some form of modification to HOV lane operation with the aim of achieving greater effi- ciency (Cambridge Systematics and URS, 2002). The 2005 opening of the I-394 HOV lanes to MnPASS tolled vehicles, creating the current I-394 HOT lanes project, is a direct response. In contrast, even without the capability to quantify bus operations benefits, the HOV lanes evalu- ation for Los Angeles County concluded that, in general, the "carpool lanes appear to have been good investments." This conclusion was drawn by applying the state standard Cal-B/C model, modified to the extent required by analyzing projects actually in operation at a point part-way through the analysis period. In addition to not including bus operations benefits, mode shifts to HOV and emissions reduction benefits were also not addressed. Accident reduction benefits were excluded lacking conclusive evidence of enhanced safety. Data limitations did not allow the San Bernardino Transitway (I-10) or the Century Freeway (I-105) HOV lanes to be assessed, but all of the other 14 study segments were subjected to comprehensive benefit-cost analysis. Benefit-cost ratios of 0.9 to 36.2 were computed, averaging 10.0 where 1.0 is the break-even point. The median was 7.4. Economic rates of return ranged from 5.1 percent to 171.6 percent, averaging 41.9 percent, with a median value of 26.6 percent (Parsons Brinckerhoff et al., 2002a). 6 The $152 per revenue bus hour figure is specific to the METRO HOV lane express operations. Thus, as it reflects fully allocated costs, it includes capital depreciation not only for expenses such as bus vehicle purchases but also for HOV-specific capital costs such as park-and-ride lots and ramps. As a general rule, the bus oper- ating cost would be roughly half of the fully-allocated cost. 2-94

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The Los Angeles County benefit-cost computations did not take accident costs into account, lacking conclusive evidence of any safety differential between having and not having HOV lanes (Parsons Brinckerhoff et al., 2002a). Subsequently, using before and after accident record analysis in a differ- ent region, a Texas Transportation Institute study found injury accident rates to have been increased by installation of concurrent flow HOV lanes having both their inside shoulder and painted buffer in the 2-to-3-foot-wide range. The injury crash rate increase found for the Dallas lanes in question was 41 to 56 percent. Injury crash rates for a moveable-barrier-separated reversible HOV lane with a 10-foot inside shoulder were not affected by HOV lane introduction (Urban Transportation Monitor, 2004b). A benefit-cost analysis of five Dallas and two Houston HOV facilities was made earlier using the MicroBENCOST economic analysis tool developed under NCHRP Project 7-12. Accident rates were at least nominally taken into account, although the researchers did note that overall a large number of careful assumptions were required for MicroBENCOST application to HOV lanes. The analysis found benefit-cost ratios of 6 to 48 for the Texas HOV lanes with an average benefit-cost ratio of over 17. Perhaps more to the point, when benefit-cost ratios of the actual HOV lanes were compared with benefit-cost ratios for constructing a GP lane in each direction, the HOV lane solution was found to be 12 to 180 percent more effective. The added benefit averaged across the seven facilities was 73 per- cent (Daniels and Stockton, 2000). Indicators of Success The preceding synthesis and analyses, most particularly in the "Travel Time Savings" and "Bus Service, Urban Area, and Facility Characteristics" subsections of "Underlying Traveler Response Factors," suggest the following "indicators of success" for HOV facilities. Most of these indicators are not absolute fatal flaw tests when taken individually, but most should be met for there to be some reasonable assurance of a satisfactory outcome for a major freeway-type HOV facility or lane installation. Urbanized area population of over 1.5 million. Orientation, preferably radial to a city center, focusing on major employment centers with preferably more than 100,000 jobs. Geographic barriers, such as bodies of water, that concentrate development and travel patterns and constrict traffic flows. Realistic potential for considerable bus volumes using the facility--25 to 30 buses in the peak hour or more. Congestion in the GP traffic lanes--freeway speeds regularly dropping below 35 miles per hour (Schofer and Czepiel, 2000). Peak-hour time savings of preferably 1.0 minutes per mile or more (at least 0.5 minutes per mile), or a total savings of preferably 7.5 minutes (at least 5 minutes). Use of the most lenient HOV eligibility requirements consistent with safety, maintenance of free-flow traffic conditions, and environmental objectives. 2-95

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In addition, it is highly desirable that public agencies be prepared to install, offer, or arrange: Support facilities and services, including park-and-ride and park-and-pool lots, bus stop facil- ities, downtown bus lanes, HOV price discounts or free passage on toll facilities, and rideshare programs with accompanying travel demand management (TDM) strategies. Outreach to key policy stakeholders and the media to explain the purpose and benefits of the HOV lanes and facilities, along with vehicle occupancy requirements--before the project opens, during the initial phases, and on an ongoing basis. Public information campaigns--accompanying the opening of an HOV facility and ongoing-- to promote transit, carpooling, and vanpooling and discourage use violations. Finally, it is essential to accept 2, 3, or more years of initial operations at lower than desirable lev- els of utilization while bus, carpool and vanpool use develops. Modification and Expansion of HOV Functions The development and operation of HOV facilities has evolved over the past 30 years. Initial pro- jects were bus-only demonstrations. Vanpools and carpools were added to the mix on most pro- jects during the 1970s and 1980s in the interest of maximizing use. Most recently, value pricing and HOT lanes have been initiated in some areas, harnessing economic incentives to mitigate demand in peak periods and permitting lower-occupant and/or single-occupant vehicles to use HOV lanes for a fee. BRT projects are being linked with HOV facilities or HOT lanes in some locales. The evolution of HOV facilities reflects a number of trends and influences. A key impetus behind the initial development and ongoing operation of HOV projects has been the continued increase in vehicle volumes and concomitant growth in metropolitan area traffic congestion. Urban road- way congestion has increased and spread in response to continuing expansion of personal travel fueled by population and employment growth, outward-shifting land use patterns, and greater affluence. Federal policies and programs have influenced HOV facility development, starting with the early bus-only demonstration projects and on to the policy shift allowing carpool use, to limi- tations on some project funding categories, to legislation allowing motorcycles and ILEVs in with HOVs, to allowing, promoting, and contributing financially to value pricing demonstrations and continuing projects. HOV facilities are almost universally undertaken in response to specific needs, constraints, and opportunities in congested travel corridors, characteristics of which often vary widely from place to place. The result is different approaches in different areas, ranging from bus use of shoulders, to HOV by-pass lanes at ramp meters, to contraflow lanes with moveable barriers, to provision of new priced lanes with HOV inducements. Environmental and energy concerns have shaped and will continue to influence HOV facility evo- lution. They have played a major role in energizing urban communities to question conventional road capacity expansion, as have ever diminishing land availability and concerns with neighbor- hood cohesion and livability. Cost of providing additional road capacity, especially in urban areas, has escalated even as revenues from traditional sources have remained flat--or even declined in real terms--given heavy reliance on traditional fuel based road user charges in a time of increas- ing fuel efficiency combined with aversion to per gallon fuel tax increases even for purposes of inflation tracking. 2-96

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These factors have made it extremely difficult to add GP road capacity in most urban areas even as congestion has become more severe and endemic. While needs for congestion relief--both real and as perceived by travelers stuck in traffic--have gone unmet, a backlash against HOV lanes has been seen in a number of locations. As illustrated in Tables 2-2 and 2-8 among others, a significant majority of HOV facilities have operated well below their vehicle carrying capacities. To many GP lane users, who typically constitute a significant majority of total corridor travel, these lanes appear "underutilized" and "inefficient." Such negative perceptions of HOV lanes have only grown as congestion in the GP lanes has progressively worsened (Bhatt, 2003). The need to expand financ- ing options, minimize construction of additional lanes, and show better and more universal uti- lization of HOV lanes, has made value pricing a more publicly and politically acceptable option. The availability of electronic toll collection (ETC) has made it technically viable. It is in this context that managed lane solutions such as HOT lanes have begun to be considered seriously and even implemented. They promise much needed additional capacity and some reduc- tion in main lane congestion. HOT lanes also offer a new travel "option" of priced congestion-free travel for those who might need it on particular days. Value pricing approaches also promise to safeguard level-of-service for HOVs through the use of varying toll levels set, in response to demand, to ensure free flow speeds. The potential to reduce congestion without major road expan- sion and generate revenues to pay for costs has generated reluctant support from the environ- mental community. While the early expectation of financially self-sufficient introduction of HOT lane functions is not likely to be fulfilled except in a few unique sets of circumstances, the approach still covers significant costs. The key factors underlying HOV facility introduction and consideration of HOT lane and other value pricing options are expected to play an even more crucial urban transportation role in the foreseeable future in the United States (Bhatt, 2003). It appears that HOV facilities or managed lane derivatives will continue to be used selectively to meet the diverse travel needs in different met- ropolitan areas and in different travel corridors within those areas. As with other transportation elements, there is no one right HOV facility or managed lanes approach for all metropolitan area or travel corridor situations. HOV facilities currently accommodating high bus and carpool vol- umes may experience little change other than enhancements to squeeze even more efficiency out of their operation. Opportunities for new HOV or managed lane applications may arise as older freeways undergo needed reconstruction. Installations where consensus develops that existing HOV capacity is not being utilized efficiently may be candidates for value pricing and priority for environmentally preferable vehicles. Managed lane options will likely also apply where HOV use under the designated occupancy requirement begins to overwhelm the facility and either occu- pancy requirements need to be raised or combinations of strategies applied. Future managed lane possibilities may include various combinations of an HOV component, pricing, and consideration of other possible user groups, including commercial vehicles (Bhatt, 2003; Turnbull, 2005; Collier and Goodin, 2004). The four presently under-construction bi-directional value-priced lanes replac- ing the Katy Freeway (I-10) reversible HOT lane in Houston will provide a "Virtual Exclusive Busway" under agreement that guarantees the transit agency 25 percent of the managed lanes' capacity for buses and for toll-free peak-period peak-direction travel by HOV 3 carpools (Poole and Balaker, 2005). The five or so HOT lane and similar projects put in operation across the United States in the past decade took long periods of careful planning and outreach before major concerns were addressed and the proposals became acceptable to the constituents. Even though, by and large, these projects are meeting principal objectives and generally show a high level of satisfaction and acceptance among travelers, each new proposal will surely require its own careful examination and consulta- tion with decision makers and the general public. Experience tells us that both HOV and managed 2-97