Travel Survey Manual Appendices - Federal Highway Administration

323 Pages·1997·14.32 MB·English

Travel
Survey
Manual
Appendices
Travel Model Improvement Program
Travel Survey Manual - A~~endices
June 1996
Prepared by
Cambridge Systematic, Inc.
Prepared for
U.S. Department of Transportation
Federal Transit Administration
Federal Highway Administration
Office of the Secretary
U.S. Environmental Protection Agency
Appendix A
The Costs of Travel Surveys
The Costs of Travel Surveys
Travel surveyors are almost always constrained by limited available
resources. More often than not, the survey design and sampling tasks are
bounded by funding limits, so the survey team needs to be able to esti-
mate the cost of various types of surveys early in their effort.
Estimating Costs Based on Previous Survey Efforts
The most common source of rough cost estimates is the reported costs of
previous efforts. The costs of travel survey efforts are often reported in
technical papers and reports. In addition, rules-of-thumb about survey
costs are commonly cited. For instance, many surveyors use a figure of
$100 per completed survey for telephone-mail-telephone household travel
surveys.
Unfortunately, there are several problems with relying on past survey
experience in estimating costs:
l The analyses rarely account for inflation;
l The analyses do not account for deteriorating cooperation rates over
time;
l The analyses do not account for geographic differences;
l It is often difficult to determine which survey cost elements are
included in the past cost estimates; and
l It is highly unlikely that the past efforts will include the same survey
design=le-ments and sampling considerations as the survey team’s pro-
posed effort.
To analyze the cost of a past survey effort, the survey team needs to
account for inflation. If the year of the past survey is known, then this is a
fairly trivial calculation. However, this step is commonly ignored. This is
particularly true with rules-of-thumb. It is impossible to lCIIOWwhether
these estimates have been developed in the recent past or whether they
have considered the effects of inflation.
Even if past costs are adjusted for inflation, the cost estimates will not take
into account the increased difficulty of getting respondents to cooperate
with survey efforts. Cooperation rates and response rates are dropping
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Travel Survy Manual A-1
over time for all types of surveys, and the increased difficulty of com-
pleting surveys has a direct effect on survey cost. For instance, consider
this extreme example. A 1964 home interview survey had an estimated
cost per completed interview of $12. If that cost is adjusted for inflation,
the estimated cost per completed interview would be about $50. In reality,
the 1995 cost for a home interview survey similar to that conducted in
1964 would be much higher (almost certainly more than double) than $50
per completed survey. Response rates for these types of surveys have
diminished drastically over the years to the point that these types of sur-
veys are not generally considered to be feasible.
The survey team must also be careful in using cost estimates from other
locations. The availability and cost of survey worker labor differs from
city-to-city. Many cities have large pools of temporary workers and
University students that can be tapped for fieldwork and office jobs.
Others do not. In addition, the cost of facilities and equipment are likely
to be different from city-to-city. Finally, some survey locations have spe-
cial characteristics that will affect the cost of the survey work. For
instance, in estimating the cost of a roadside handout survey to be
conducted at a barrier toll facility, the survey team should not use past
survey examples in which toll collectors were asked to distribute ques-
tionnaires unless the new survey effort will also be using the toll collec-
tors. Some toll roads will require survey teams to supply fieldworkers at
the toll booths, while others will prevail upon the collectors for survey dis-
tribution.
The response rates and cooperation rates from different locations are also
likely to be quite different, which means that the amount of survey worker
labor may be significantly different in different locations. For instance,
completing 1,000 30-minute telephone interviews with a 50 percent
response rate is likely to cost $10,000 to $20,000 less than completing 1,000
30-rninute interviews with a 33 percent response rate.
The final two potential problems with using past survey efforts as a guide
in estimating survey costs are related to the way that survey costs are
commonly reported. In order to use a past survey cost estimate effec-
tively, the survey team must understand exactly which survey elements
the estimate included. Most reported estimates are the cost to the agency
of one or more survey contractors. These costs are a problem, because:
. They do not include the considerable time and effort expended on the
survey by agency staff;
. Contractors are responsible for different survey elements in different
survey efforts;
They do not reflect the actual cost of the survey to the contractor, only
l
the contract price.
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Therefore, when a survey team sees a cost estimate for a past survey effort,
they should seek as much detail as possible about what it includes and
how it was calculated. In general, the best cost estimates for a survey
effort are the costs of very recent surveys conducted in the same geo-
~aphic location. Non-transportation surveys with these characteristics
are probably better measures than older transportation surveys or trans-
portation surveys performed in different places. If possible, the survey
team should enlist the assistance of a local marketing research expert to
obtain abetter understanding of current local survey costs.
Developing Cost Estimates from Unit Costs
In addition to (or instead of) relying on past survey efforts at the begin-
ning of a survey design effort, the survey team should try to develop cost
estimates by considering each survey element. Fairly accurate estimates of
likely costs can be developed with a little effort. Using simple spreadsheet
software will allow the survey team to test different assumptions about
response rates, labor and equipment costs, and different survey designs.
For each type of travel survey, there are fixed and variable costs. The
labor costs for interviewers and fieldworkers are almost always the most
important cost elements for telephone and personal intercept surveys
(either interviews or questionnaire distribution). The primary expenses
for mail surveys are usually postage and printing.
Table A.1 summarizes the cost components of travel surveys. The specific
costs for a survey effort need to be developed based on the potential sur-
vey design(s) and on the survey team’s specific plans.
The following discussion describes an example of how a survey team
might estimate survey costs based on unit cost assumptions.
A survey team needs to perform vehicle intercept surveys at five locations
on the perimeter of a study area. Each location needs to be surveyed in
one direction, and they all average about 8,000 vehicles per day in that
direction. Because of past logistical difficulties with working with DMV
data files, the survey team does not wish to consider a license plate sur-
vey. However they would like to compare the costs and benefits of con-
ducting a roadside handout survey and a roadside interview survey.
The survey team has identified a number of individuals that would be
suitable for the fieldwork, so the team would like the crew to intercept
platoons of five vehicles at a time, ask drivers a single screening question,
and then either hand them a mailback form to complete or conduct a short
interview. The survey team believes that the following efficiency levels
will be achieved by the two methods:
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Handout/
Mailback Interview
Average platoon assembly time (min.) 2 2
Average data collection time (min.) 1 5
Average platoon releasetime (min.) 1 3
Timebetween platoons (min.) 2 2
Totalplatoon cycletime(min.) 6 12
Platoons perhour 10 5
Vehiclesperhour 50 25
Vehiclesper day (12hours) 600 300
Both survey methods will require automatic counting equipment, signage,
and safety equipment. The anticipated site design for the handout survey
will require the daily rental of $600 of equipment per survey site. The
interview survey will require $800 of equipment per survey site.
Based on past experiences, the survey team expects the following response
from the two survey methods:
Handout/
Mailback Interview
Cooperation rate (respondent agrees to interview 95% 8570
or accepts questiomaire)
Completion rate (respondent completes survey) 25 95
Percent ofcompleted surveys that areusable 90 95
Percent ofcontacts yielding usablesurvey data 21 77
Tables A.2 and A.3 show the cost estimation calculations. In this case, the
roadside interview survey is the more cost effective method. However,
the survey team needs to weigh the reduced cost against the added traffic
disruption of the method.
A-6 Travel SurveyManual
Table A.2 Assumptions Used in Survey Costing Example
Handout/Mailback Interview
Survey Survey
First Each Other First Each Other
Site Site Site Site
.
Survey Design and Analysis
Senior Analyst hours 60 0 60 0
Junior Analyst hours 80 0 80 0
Administrative hours 120 0 120 0
Training
Number ofSupervisors 1 0 1 0
0
Number ofTechnicians 8 8 0
Training Hours 3 0 3 0
Survey Station SetupPeriod
Number ofSupervisors 1 1 1 1
Number ofTechnicians 2 2 2 2
Number ofPoliceOfficers 1 1 1 1
Setup Hours 1 1 1 1
DataCollection Period
Supervisors 1 1 1 1
Interviewers (number ofvehiclesinplatoon) 5 5 5 5
Flaggers 1 1 1 1
Counters 1 1 1 1
PoliceOfficers 1 1 1 1
Spare technicians 1 1 1 1
Data collectionhours 12 12 12 12
SiteEquipment
Signage/Safety Equipment $400 $400 $600 $600
Automated trafficrecorders 200 200 200 200
Total Equipment -iim $600 $800 $800
Traveland PerDiem
Fieldworkers 9 $;
Average Cost per Fieldworker $25
cost $225 $225
StationEfficiency
Average platoon assembly time(rnin) 2 2 2 2
Average data collection time (rein) 1 1 5 5
Average platoon releasetime (rein) 1 1 3 3
Travel Survey Manual A-7