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CHAPTER 4
Data Collection
The literature review found that various methods have ods include traveler intercept surveys, field laboratory stud-
been used to measure traveler perceptions of quality of ser- ies, and video laboratory studies. Introductory material on
vice (i.e., field surveys, video laboratory surveys, simulator customer satisfaction survey techniques can be found in
surveys, telephone surveys, and web surveys). The literature Trochim [72].
review revealed the wide range of customer satisfaction meas-
urements used and the wide range of variables that re- · Traveler Intercept Surveys directly measure the LOS per-
searchers had determined to be critical for predicting or ceptions of actual travelers making real trips. These surveys
measuring traveler perceptions of quality of service. Some of intercept travelers mid-trip and either orally interview
the differences could be attributed to differences in survey them on the spot or give them a postcard to report their
methods. Other differences could be attributed to differences LOS perceptions at a convenient time after they have com-
in the situations to which the survey participants were pleted their trip. The Noel, Leclerc, and Gosselin [73] study
exposed. Still other differences could be attributed to differ- of rural bicycle LOS used this method to measure bicycle
ences in how quality of service was defined (or left undefined) LOS on rural roads.
for the participants. In addition, all surveys were limited to a · Field Laboratory Studies recruit subjects (paid or unpaid
single metropolitan region, so it was not possible to rule out volunteers) to travel over a fixed course in the field and
the potential effects of geographic location on the reported report their LOS perceptions at strategic points along the
LOS models. course. The "Bike for Science" and "Walk for Science" stud-
The objective of the data collection task was, therefore, to ies by Landis et al. [74] [75] are examples of this approach
develop and execute a set of quality of service surveys that to measuring traveler perceptions of level of service.
could be uniformly and consistently implemented across all · Video Laboratory Studies show recruited subjects film clips
modes and in several different metropolitan areas of the of various street situations in a video laboratory setting. The
United States. Pecheux et al. [76] and Sutaria and Haynes studies [77] for
All prior quality of service surveys had been limited to a intersection level of service are two examples of this ap-
single site in a single urban area. One of the major purposes proach to measuring traveler perceptions of level of service.
of the new data collection under NCHRP Project 3-70 was to
gather data using a consistent method across multiple urban The level of service research to date is split fairly evenly be-
areas to determine if LOS perceptions vary significantly tween the use of field laboratory settings and video laboratory
across urban areas of the United States. settings for measuring traveler perceptions of level of service
The data collection task of this project was conducted in (see Exhibit 34). Traveler intercept surveys have been used by
two phases. Various data collection methods were pilot tested a few researchers to measure traveler LOS.
during Phase 1. The data collection effort for the project was Traveler Intercept Surveys, Field Laboratory Studies, and
completed in Phase 2. Video Laboratories Studies each have their relative strengths
and weaknesses (see Exhibit 35).
The traveler intercept surveys can gather responses from
4.1 Selection of QOS Survey Method
large numbers of individuals, but only for the particular trip
Several different methods have been used in the literature that they made on the facility--the researcher obtains only
to measure traveler perceptions of satisfaction. These meth- one data point for each individual responding to the survey.
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Exhibit 34. Traveler Perception Survey Methods in the Literature.
Research Team Data Collection Method LOS Model
Auto
Hall, Wakefield, and Kaisy [78] Focus Group Discussions Freeway
Pecheux et al.79] Video Laboratory (100 subjects) Signalized Intersection
Sutaria and Haynes [80] Video Laboratory (310 subjects) Signalized Intersection
Nakamura, Suzuki, and Ryu [81] Field Laboratory (24 subjects) Rural Road
Colman [82] Field Laboratory (50 subjects) Urban Street
Transit
Morpace [83] Traveler Intercept Survey on-board vehicle Route
Bicycle
Landis et al. [84] Field Laboratory (60 subjects) Intersection
Harkey, Reinfurt, and Knuiman Video Laboratory (202 subjects) Segment
[85]
Jones and Carlson [86] Video Lab. Over Web (101 subjects) Rural Road
Noel et al. [87] Traveler Intercept Survey (200 subjects) Rural Road
Landis, Vattikuti, and Brannick Field Laboratory (150 subjects) Segment
[88]
Stinson and Bhat [89] Video Lab. Over Web (3,145 subjects) Segment
Pedestrian
Miller, Bigelow, and Garber [90] Simulated Video Lab Intersection
Landis et al. [91] Field Laboratory (75 subjects) Segment
Chu and Baltes [92] Field Laboratory (96 subjects) Mid-block Crossings
Nadeir and Raman [93] 3-D Video Simulator Segment
Traveler intercept surveys may be the most realistic in that Once the video clip has been assembled and calibrated, the
travelers are in an actual trip-making situation; however, the cost per data point obtained is lower than that for traveler
particular method used to intercept travelers may bias the intercept surveys, but higher than for field laboratory studies.
results, especially, if the traveler is detained a long time or if The cost per subject though is higher than for the traveler in-
certain "hard to stop" travelers are not interviewed or given a tercept surveys, because video labs typically test fewer subjects
post card. Also, there may not be enough travelers on truly than would be found in an intercept survey.
poor road sections to survey. The video labs and field laboratories test fewer subjects
Although the initial investment for traveler intercept than the traveler intercept surveys; however, both laboratory
surveys, and the cost per each subject are quite low, the cost studies can expose single subjects to multiple conditions, thus
per data point obtained (i.e., the product of the number of enabling researchers to distinguish between a single subject's
individuals surveyed and the number of situations they reaction to a range of situations and differences in multiple
were exposed to) is higher than for the other data collec- subjects' reactions to the same situation. This capability
tion methods (if one considers only the marginal costs (highly valuable for model building) is not available in the
and ignores the high initial investment costs of the video traveler intercept surveys.
laboratory). The traveler intercept surveys are better for general model
The field laboratory studies also have low initial invest- validation than for detailed model development. Video labo-
ment costs, and they have the lowest cost per data point ratory and field laboratory studies are better for model devel-
obtained. However, they are expensive to set up for a given opment because they give researchers more control over the
site and have a high cost per subject. Each subject, however, variability of the results.
is exposed to a wide variety of situations in the field, so this Field surveys of traveler satisfaction, such as the FDOT/
method generates numerous data points per individual. Sprinkle "Walk For Science" surveys, come closest to the real
Field laboratory studies are realistic in that they expose the world experience of travelers while controlling for the range
volunteer subjects to the full sensory experience (all five of conditions they experience. However, this survey method
senses) of field conditions; however, because there is no is expensive and prone to agency liability problems (caused
penalty for arriving late at one's appointment or job the re- by exposing the participants to specified field conditions they
alism of the trip experience is questionable. might not otherwise attempt on their own). Conducting field
Video laboratory studies require an initial investment to surveys of traveler satisfaction would have cost $150,000 per
create the video clips. If there is doubt about the ability of mode per site to set up and conduct. For four modes and four
the video to capture all of the factors affecting a traveler's cities, the data collection cost alone would have exceeded the
perception of LOS, then there is also an added expense for entire research project grant. Thus field surveys were deemed
calibration of the video lab LOS results to the field. infeasible.
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Exhibit 35. Validation Data Collection Options.
Survey Type Strengths Weaknesses Cost
Traveler 1. Most realistic of all 1. No control over subject's Initial
Intercept methods. Only exposure to facility conditions. Investment:
Surveys: method that captures 2. Limited information on extent $20,000 to pilot-
Surveyors stop traveler's response of subject's exposure to facility. test intercept
people mid-trip while making a real 3. Can't test the same person's methods.
to distribute post trip. response to conditions other
cards or conduct 2. Can test for effects than those of specific trip.
survey. of travel time, wait 4. People don't like to be Data Collection:
time, and cost in interrupted while traveling, $15,000 per site for
combination with which may bias results. four modes.
physical 5. Can't sample extreme
characteristics of conditions. $60 per data point
facility. 6. Modal sample sizes depend on (not counting initial
volumes. Bicycles are difficult to investment)
sample adequately.
Field 1. Second most realistic 1. Potential liability for accidents. Initial
Laboratory: of survey types. It 2. Can't expose subjects to Investment:
Paid or unpaid puts subjects in conditions not present in $-0- because
volunteers travel realistic physical community or at time of test, method is well
specified course. situations, lacking particularly true for surveys tested.
only the realism of using weekend volunteers.
making the actual 3. Because subjects are not
trip for an actual actually going anywhere the Data Collection:
purpose (such as usual factors that influence trip- $150,000 per site
going to work). making behavior (travel time, per mode.
2. Good control on wait time, and cost) cannot be
subject exposure to reliably included or ruled out. $10-$25 per data
facility. 4. Unpaid volunteers are self- point.
selected. (not counting initial
investment)
Video 1. Controlled exposure 1. Not as realistic as simulator or Initial
Laboratory: of subjects to audio- field tests. Some important Investment:
Selected visual aspects of aspects of trip are excluded $55,000 to develop
subjects shown travel. (e.g., pavement condition and videos for three
video clips in 2. Little liability rumble and back draft from modes. Another
laboratory exposure. trucks passing the subject). $125,000 to
setting. 3. Can expose subjects 2. Factors that influence trip- calibrate to field.
to wide range of making behavior (e.g., travel
conditions and time time, wait time, and cost) Data Collection:
periods, thus cannot be reliably tested. $64,000 per lab site
enabling more in- 3. Needs calibration/validation for three modes.
depth analysis for against field conditions.
each individual. 4. Not realistic for Transit. $42 per data point
(not counting initial
investment)
Compared with the "Walk For Science" field surveys, trav- adversely affecting their perception of the quality of service.
eler intercept surveys sacrifice the ability to "control" the Consequently it was determined that this survey method
range of physical conditions to which the participants are could not be used for the auto or bicycle modes.
exposed. In addition, the travelers are self-selected (i.e., they This left video lab surveys as the best remaining method for
would not be there to be intercepted, if it were not already surveying auto and bicycle level of service, because of its rel-
their preferred mode and route). Nevertheless, among the atively low cost, the ability to control the environment to
remaining feasible survey methods, traveler intercept surveys which each participant was exposed, the elimination of
were the best method for gathering transit rider quality of research agency liability exposure, and the ability to expose
service perceptions. They were within the budget range of the different people from different geographic areas to the same
research grant and travelers were exposed to the full physical perceived street environment.
experience of the transit experience. Although it would have been feasible to use a traveler in-
The traveler intercept survey method however was prob- tercept survey method for pedestrians, the video lab survey
lematic for auto and bicycle LOS because it is difficult to method was considered superior because it would enable the
intercept auto drivers and bicyclists on the street without team to expose survey participants to a controlled wider
