Departure Time
In some cases, the rMove app may have detected the start of a trip
after its true start time, which can yield invalid or extreme values for
trip duration and speed. In these cases, the fields depart_date,
depart_hour, and depart_minute were adjusted for “late pickup”
conditions using the following approach:
- Departure time was imputed using the median speed between all
locations along the trip, excluding the origin point, and the distance
between the origin and the next point on the trip. For trips with fewer
than three recorded locations, imputed departure time is set three
minutes earlier than the original departure time to compensate for
rMove’s 3-5-minute ping interval. Note that some trips that are the
result of split loop trips may only have three or fewer points but will
use the imputed depart time from before the loop trip was split and thus
may not be included in this rule.
- If the imputed departure time overlaps with the previous trip’s
arrival time, the previous trip’s arrival time was instead used as the
departure time. Regardless of the number of locations along a trip, if
the imputed departure time was later than the initially reported
departure time, the imputed departure time is set to the original
departure time. User-added trips as well as long distance passenger mode
trips are also set to the original departure time, as user-added trips
are not subject to “late pickup” conditions, and long-distance passenger
modes are often plane trips where all collected traces contain speed
information from other modes and thus are less reliable (as rMove cannot
collect locations when a phone is in “airplane mode”).
Duration and speed are calculated based on the imputed departure
time.
Purpose
Respondents report the purpose of the trip destination in each trip
survey. The origin purpose is derived from the destination purpose of
the previous trip, except for the first trip in the travel period or
where an rMove trip occurs after a trip with item non-response. For the
first trip in the travel period, the origin purpose can be inferred from
“begin_day” in the day table.
When purpose was not asked because an analyst split a user-reported
trip during data cleaning (creating a new destination along a trip),
purpose values are derived where possible based on proximity (within 150
meters) to estimated home, work, or school locations. If the location is
not proximate to home, work, or school locations, the purpose is set to
“other.”
The purpose category variables (o_purpose_category,
d_purpose_category) contain aggregated purpose values based on the type
of purpose at the origin/destination of each trip. Dataset users are
welcome to perform their own recoding of the purpose categories as
well.
Trip purposes have been imputed in cases where a purpose reported by
the user is assumed to be inaccurate based on information about that
person’s reported habitual locations and other trips (primarily to home,
work, and school locations). The trip purpose imputation approach was
applied to all rMove trips in person-days with at least 1 complete trip
and no more than 10 incomplete trips. (“Incomplete” trips are trips for
which the respondent did not answer the trip-specific survey questions
about purpose, mode, etc. for the given trip.)
The approach was to apply various “tests” in logical sequence to
trips for which the stated purpose is not consistent with the location
type based on the reported habitual locations. In general terms, the
tests were designed to:
- Check the respondent’s reported destination purpose when it
conflicts with the destination location type. (The details of the tests
depend on the trip purpose, with different criteria used for change-mode
trips, escort trips, linked transit trips, trips with home destinations
but other reported purposes, etc.)
- Identify cases where respondents swapped the order of two or more
trips when reporting their details.
- Identify cases where respondents may have omitted a trip and shifted
remaining reported trip details by one trip when reporting the rest of
their trips.
- Fill in missing data by sampling destination purposes from other
trips made to the same locations, either by the same respondent or by
other respondents.