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In summary, 10.8 percent of responding office workers reported shifting from driving alone or car- pooling to using bus or rail transit at their new rail-served TOD workplace, while 8.8 percent of respondents reported shifting from rail or bus transit to driving alone or carpooling. This produces a net estimated shift by responding workers to transit of 2.0 percentage points. When walk and bike commute modes and drive alone/carpool shifts are included along with transit, the shifting into transit, walk, bike, and carpool commuting (19.7 percent) exceeds the reverse (18.6 percent) by 1.1 percentage points (Lund, Cervero, and Willson, 2004a). The results would be more markedly favorable for trip reduction were it not for the finding that almost twice as many workers shifted from walking or biking to auto for their commute as the other way around, a phenomenon explored further below. Vehicle Trip, VMT, Energy, and Environmental Relationships Reductions in automotive trips and vehicle miles of travel (VMT), although they can result from decisions not to travel at all, come primarily from either mode shifts or reductions in trip length. The preceding subsection presented what concrete information there is about actual shifts in mode that occur when households and workers move into TODs. The extent of such shifts is presumed to afford the best measure of regional TOD impacts on overall mode shares. The small number of explicitly published quantitative observations range from 2 to 16 percentage points increases in the transit mode share for the commute trip, with the one such reporting for non- work travel indicating a 12 percentage points transit share increase. Net reported effects on auto use for commuting range from just one side or the other of no change to a 14 percentage points decrease in auto commuting overall, with the one observation available for non-work travel indi- cating a 14 percentage points reduction in drive-alone share. A puzzling finding from the limited data is the reporting of decreases in walking to work upon residency or workplace relocation to TODs. (A major exception is provided by results of the 8-site 2005 Portland surveys, which show a 2.3 percentage-point increase in walking to work and no change in bicycling upon station-area residency.) The reports of walking decreases make one wonder if some unidentified complexity isn't at work, perhaps resulting from comparing "before" situations typically reflecting significant time at a location (just before a move) with "after" situa- tions that may on average reflect shorter-term location in one place. Shorter-term location would allow less time for adjustments, particularly for achieving a home-work location relationship that allows walking or bicycling to work. A next-best measure of TOD effects on regional mode shares is to compare TOD mode shares with mode shares for surrounding or other selected non-TOD areas. Such cross-sectional analyses do not, unfortunately, engender the same degree of confidence as an indicator of what actually happens when a resident moves from outside to inside a TOD, due to many unanswered questions about causality. Nevertheless, continuing research suggests that "although different types of analyses can yield different answers" careful neighborhood comparison studies are not completely off the mark (Handy, Cao, and Mokhtarian, 2005). The same 2003 California TOD travel characteristics study that obtained marginal results in surveying automobile commute mode shifts found quite clearly through station-area survey and 2000 Census analysis that commute shares of residents within an 0.5-mile radius around the rail stations of TODs differ from the shares of those outside. The statewide weighted average difference in transit shares compared against the surrounding 0.5 mile to 3.0 mile 17-93
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donut was nearly fourfold--27 percent transit inside the 0.5-mile radius and 7 percent outside. Comparing against citywide commute shares, the transit use differential was fivefold, the same as had been found in the 1992 California transit-focused development study (Lund, Cervero, and Willson, 2004a). (For more on this analysis see "Response by TOD Dimension and Strategy"-- "Response to TOD by Land Use Mix"--"Residential.") Resident surveys in six Metra commuter rail (CRR) station commutersheds found their market penetration to drop from 15 percent within an 0.5-mile radius to 7 percent at 0.5 to 1.0 miles and 3 percent at 1.0 to 2.0 miles (S.B. Friedman & Company et al., 2000a and 2000b). (For more see "Underlying Traveler Response Factors"--"Land Use and Site Design"--"TOD Supportive Design"--"Walking Distance and Transit Access/Egress Modes"--Table 17-27). On the workplace side of the equation, comparing office workers within an 0.5-mile radius around the rail stations of TODs with workers regionwide, the 2003 California study found an average station area transit commute share of 19 percent compared to 5 percent regionwide. The station areas with TODs had worker transit shares three-and-two-thirds times higher on average than the surrounding regions (Lund, Cervero, and Willson, 2004a). (See Tables 17-19, 17-20, and 17-21 for workplace survey locations). Opportunity to eliminate vehicle trips and VMT is presented not only by the possibility of alter- ing the prime mode of travel but also by the strong likelihood that trips to access transit stations from the home can, with TOD residency, be shifted out of the auto access mode. Although no before-and-after-TOD data on choice of mode for access to the transit station were located, there is considerable information on effects of distance to a transit station on the mode of access choice. Moreover, there is relatively little doubt that these effects will largely or fully translate into mode- of-access change with a move to residency closer to a transit stop. An example of data relating transit access mode choice to distance from one's station was provided in Table 17-26 in connection with the Metra study referred to above. The proportion of commuter rail passengers walking to the station was found to drop from 82 percent within an 0.5-mile radius to 41 percent at 0.5 to 1.0 miles and 8 percent at 1.0 to 2.0 miles. Reported auto use for access was only 7.5 percent drive alone and 0.4 percent carpool within the 0.5 mile radius, rising sharply to 33.4 percent drive alone and 2.9 percent carpool at 0.5 to 1.0 miles and on up to 63.7 percent drive alone and 5.9 percent carpool at over 2.0 miles (S.B. Friedman & Company et al., 2000b). Equivalent data for HRT is graphed in Figure 3-3, "Mode of access for commute trips from home to all BART stations," presented in Chapter 3, "Park-and-Ride/Pool," under "Related Information and Impacts"--"Usage Characteristics of Park-and-Ride/Pool Facilities"--"Mode of Access"--"Bay Area Rapid Transit (BART)." For the minority of TOD residents who would continue to drive to a transit station after moving into a well-situated TOD, their trip is obviously reduced in length and related VMT production. No information at all has been encountered on the subjects of overall trip length or VMT reductions upon moving into TODs or VMT differentials between TOD and non-TOD areas per se. Research on VMT effects of development density, land use mix, and pedestrian-friendly design in general is summarized in the "Related Information and Impacts"--"Trip Making and VMT" subsection of Chapter 15, "Land Use and Site Design." See especially the "Trip Making and VMT Differentials" discussion. Available information suggests that greater density, mix, pedestrian-friendliness, and accessibility do work together to reduce VMT. These are all characteristics of good TOD design, with the transit component providing the regional accessibility. 17-94