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gating the traffic impact of new development projects and the benefits of applying development-
level TDM mitigation. The Federal Highway Administration's public version of the TDM model is
available via the FHWA website at http://www.fhwa.dot.gov/environment/cmaqeat/descriptions_
tdm_evaluation_model.htm.
Subsequent TDM modeling tools have focused more narrowly on the design and impact of indi-
vidual employer/institutional programs. In other words, the subject is an individual site, and not
a population of employers such as might be targeted under an area-wide program initiative or
ordinance. Examples of such tools include the Travel Demand Management Program software
developed for the South Coast Air Quality Management District in Los Angeles by the California
Air Resources Board (Comsis, 1993b). The research behind the development of this model was pre-
sented earlier in the "Related Information and Impacts" section under "Modeling Studies," along
with the more recent Worksite Trip Reduction Model developed by CUTR.20
Another fairly recent model, again with a single-employer focus, is the U.S. Environmental
Protection Agency's COMMUTER Model. It was developed under contract by Sierra Research,
drawing heavily from the original TDM Evaluation Model. A major literature review was con-
ducted to identify new sources of impact information for each of the strategies featured in the model
(Sierra Research, 1999). There has been a model coefficient update as of 2002 (U.S. Environmental
Protection Agency, 2005), supporting a version 2.0 of the model. Perhaps the biggest change over
the TDM Evaluation Model, other than the convenience of a modern, menu-aided user interface, is
the ability to calculate emissions. The model was created to support the introduction of voluntary
emissions reduction programs for metropolitan nonattainment areas seeking credit for air quality
conformity demonstrations. The model and version 2.0 manuals can be accessed and downloaded
from the EPA site at http:/ /www.epa.gov/otaq/stateresources/tools.htm.
CASE STUDIES
"Transportation Days" Marketing and Outreach Programs--
Cross Westchester Expressway Corridor
Situation. In Westchester County, New York, the Cross Westchester Expressway linking Tarrytown,
White Plains, and Port Chester with the New York State and New England Thruways attracted
major development during the 1970s and '80s. By 1980, the corridor had 100,000 jobs, and during
the 1980s more than 20,000 new jobs were added. By 1985, congestion during peak travel periods
was becoming routine, and long queues were occurring both morning and evening on the Tappan
Zee Bridge. A major factor in bridge congestion was the crossing of Rockland County residents
over the Hudson River to reach the jobs in Westchester County. Studies supported by Westchester
County, New York State DOT, New York Metropolitan Transportation Council (NYMTC), and pri-
vate groups identified a need for adding transportation capacity to the Tappan Zee Bridge and the
Cross Westchester Expressway. However, it was also recognized that these improvements would
be costly and take many years to accomplish. In the interim, attention was turned to making more
20 As noted in the "Related Information and Impacts" section under "Modeling Studies," CUTR issued an
update to the Worksite Trip Reduction model during the timeframe of the Chapter 19 review and publica-
tion process. The update is known as TRIMMSİ Version 2.0 and provides parameter, user-interface, and
benefit-analysis enhancements and revisions (Concas and Winters, 2009).
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efficient use of existing facilities by encouraging commuters to switch from single occupant vehi-
cle (SOV) commuting to transit and ridesharing.
Actions. In 1989, the New York State Energy Office awarded a grant to the Westchester County
Department of Transportation to "develop, market, implement, operate, support and monitor
Transportation Management Programs" for the purpose of saving energy, reducing congestion
and air pollution, and providing transportation alternatives. A specific goal of removing 1,100
SOVs from daily commuting was established. The program developed to meet these objectives
included bringing employers, developers, building managers, and local and state officials together
in an ad hoc advisory group to support program activities; conducting a survey of workers to
identify commuting patterns and needs; targeted transit service improvements; preparing a mar-
keting and information package on commuting options; presenting the marketing and informa-
tion materials in "Transportation Days" held at work places through the corridor; and evaluating
the results of the program activities.
The employee survey was distributed to over 20,000 workers at 130 employers in the corridor in
September 1990. From approximately 6,500 responses, results of the survey were used to fashion a
set of transit service modifications for implementation in the fall of 1991. Concurrently, a market-
ing and information program was developed, including a slide show with presentation script and
a Commuter Information Package. The slide show was later recorded on video for use at Employee
Transportation Days, which were conducted throughout 1992 at the work sites of 79 employers
in the corridor, representing almost 12,000 employees. Almost 3,000 information packages were
distributed through these activities, with an additional 2,500 packages distributed through other
agencies and meetings.
Analysis. In February 1993, a sample of workers who responded to the 1990 survey were recon-
tacted to obtain information on their exposure to the marketing program and any changes in com-
muting patterns. This was made possible by having obtained the employee's work phone number
in the 1990 survey. Only employees whose employer participated in Employee Transportation
Days or had received the Commuter Information Packages were contacted. Of roughly 1,300
names and phone numbers from the original survey, contact was made with 596 phone numbers.
Because of employee turnover during the 2-year period since the initial survey, the individual
answering the phone was often not the original respondent. This difference was noted and the sur-
vey was administered anyway, primarily attempting to determine whether the employee had
changed modes and the factors behind that decision.
Results. Of the 596 persons participating in the follow-up survey, 356, or about 60 percent, were
the same individual surveyed in the original survey. Thus 240, or 40 percent, were different and
considered "new" employees since the 1990 survey. Of the 356 repeat respondents, 71 (18 percent)
indicated that they had attended a Transportation Day event, compared to 31 (13 percent) of the
240 "new" respondents. Overall, 190 of the 596 total respondents changed commute mode between
1990 and 1993. Nevertheless, overall, the percentage of commuters driving alone remained at vir-
tually the same level--68.6 percent before and 69.3 percent after. In terms of vehicle trip reduction
(VTR), vehicle trips per 100 workers increased from 77.4 to 79.3 during the period, indicating that
vehicle trips actually increased by 2.5 percent.
The subgroup of respondents classified as "new" employees (not in the 1990 survey) appear to have
shown greater tendency to shift modes than those who were surveyed previously. Only 83 of the
356 "repeat" respondents, or 23.3 percent, indicated a change in mode in the second survey, com-
pared to 107 of 240, or 44.6 percent, of the "new" respondents. Whereas that higher rate of mode
shift might not be universally positive--commuters could have changed to or from driving alone--
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the "new" group also logged a better trip reduction than the "repeat" group. Drive-alone rates
for the "repeat" group increased from 66.9 percent to 69.4 percent during the program, repre-
senting an increase in vehicle trips of 5.1 percent (77.7 to 81.7). In the "new" group SOV use
declined from 71.3 percent to 69.2 percent. Vehicle trips were reduced by 0.6 percent (down from
78.3 to 77.8 per 100). A possible explanation is that the new employees were more likely to be con-
sidering alternatives during their period of transition.
Looking at the entire sample of 596 respondents, of the 409 (69 percent) who drove alone prior to
the program, 332 (81 percent) continued to drive alone after program efforts, while four (1 percent)
chose to walk, 45 (11 percent) chose to rideshare, 24 (6 percent) shifted to transit, and the remain-
ing four (1 percent) chose "other." Of those 98 (16 percent) who originally were in ridesharing, only
37 (38 percent) continued to rideshare, 49 (50 percent) switched to driving alone, six (6 percent)
switched to transit, and the remaining six (6 percent) walked or traveled by "other" means. Finally,
of those 74 (12 percent) who previously commuted by transit, 39 (53 percent) continued to take
transit, while 24 (32 percent) switched to SOV, six (8 percent) switched to ridesharing, and the
remaining five (7 percent) walked or traveled by other means. So, in effect, rideshare commuters
proved to be the least likely of all modal groups (not counting the 15 respondents originally
reporting walk or other modes) to stay with their original mode (38 percent), while those who
drove alone were the most likely to retain their original mode (81 percent)--a substantial margin
of difference.
Closest to the primary focus of the evaluation was the extent to which the marketing and informa-
tion program, and particularly the conduct of Transportation Days, was influential in triggering a
mode shift. As shown in Table 19-39, a higher percentage of workers who attended a Transportation
Day switched from driving alone (the share dropped from 68.6 percent to 63.7 percent) than did the
workers who did not attend, where drive-alone rate actually increased from 68.9 percent to 70.8 per-
cent. In general the group that attended also showed greater tendency to shift to vehicle-trip-saving
modes, including transit and walking, while those who did not attend showed only a slight shift to
transit and to "other." ("Other" has been assumed to be driver-serve-passenger or taxi.) The shifts of
the group that attended resulted in a vehicle trip reduction of 7.5 percent, while the shifts of those
who did not attend resulted in a vehicle trip increase of 4.2 percent. The question to be asked is
whether the Transportation Day strategy was responsible for the switch, or whether the persons
interested enough to attend the event were more highly disposed to considering and seeking an alter-
native mode.
Table 19-39 Employee Mode Split Before and After "Transportation Days" Marketing
and Outreach Program
Attended Transportation Day Did Not Attend Transportation Day
Mode 1990 1993 1990 1993
Walk 0.0% 2.0% 1.5% 1.1%
Drive Alone 68.6% 63.7% 68.9% 70.8%
Rideshare 13.7% 11.8% 16.9% 15.6%
Transit 16.6% 21.6% 11.5% 10.0%
Other 1.0% 1.0% 1.5% 2.5%
Vehicle Trips per 100 76.1 70.4 78.7 82.0
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