Spatial Measurement of Transit Service Frequency in Canada
Spatial Measurement of Transit Service
Frequency in Canada
Craig TOWNSEND
Abstract
This paper describes how transit service frequency data can be used together with street
network data in Geographic Information Systems (GIS), in order to analyse variation in
the intensity of transit frequency between places. The method proposed uses a gridded
mesh to standardise units of spatial area to overcome the problem of intensities which
vary based on the size and shape of spatial units. By standardising the size of spatial
units, some detailed accuracy is sacrificed, but the result is quantification that can be
used to compare changes over time, and between parts of cities, or between different
cities. The technique is summarized with analytical results from studies of transit service
in the mid-sized Canadian metropolitan areas of Ottawa and Vancouver.
Introduction
within a half mile (800 metres) walking
Greater availability and quality of data
catchment of those lines, together with the
from public transportation operating and
residential location of population (see Figure
planning agencies, together with advances
1). This type of map, using current data,
in Geographic Information Systems (GIS)
can now be produced in a few hours, using
software,
readily
have
enabled
increasingly
accessible
transportation
network
sophisticated measurement. For the last
and population data. A more recent version,
couple of decades, researchers have used GIS
drawn with GIS software shows “straight-line
software to draw “isochrones” or “buffers”
buffers” in Figure 2.
to measure the catchment areas that are
accessible by different modes of transport.
The straight-line buffer is used to measure
Previously, this work was laborious and slow
a catchment area around these points and
because it was done by hand. For example,
lines, but in places where the surrounding
in the 1920s the planners Bartholomew and
infrastructure network is not highly networked
Associates mapped Vancouver’s streetcar
(e.g. with a grid of small streets), or where
lines and the area (buffer) that was considered
there are barriers in the way, this method may
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Spatial Measurement of Transit Service Frequency in Canada
not be accurate. For this reason, others have
the transportation infrastructure configuration.
measured actual travel speed on the existing
While the map of a proposed subway for
network to draw travel time isochrones
Toronto presented travel time isochrones
around stops or stations. An old example of
from one station, other studies such as a
this approach can be found in the 1945 plan
1973 rapid transit study for Ottawa examined
for a subway in Toronto: the travel times by
isochrones from multiple stations, using
walking, subway, bus, and streetcar were
different modes of transportation. Figure 4
calculated from a central station in order to
shows travel time isochrones around proposed
measure the area that would be accessible
rapid transit stations, reachable by a 5 minute
within different time zones (see Figure 3).
walk, a 10 minute walk, or a 5 minute drive.
These measurements took into consideration
Figure 1: Electric street railway line catchments in Vancouver, 1928
PRESENT CAR LINES
AREA SERVED & POPULATION
LEGEND
UNSERVED AREAS
NOTE One Quarter Mile Walking
Distance to Car Line taken
as Basis of Service
STREET CAR LINES
BUS LINES
EACH DOT REPRESENTS
50 PERSONS
Source: Bartholomew and Associates, 1928
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Spatial Measurement of Transit Service Frequency in Canada
Figure 2: Bus and rail rapid transit catchments in Vancouver, 2009
Accessibility From Stops
Bus (400m)
B Line (600m)
SkyTrainRail(600m)
Source: Fisher et al., 2009
Figure 3: Isochrones of areas accessible by proposed subway in Toronto, 1945
- LEGEND -
0-5
5-10
MINUTE TIME ZONE
“
“
“
10-15
“
“
“
15-20
“
“
“
20-25
“
“
“
25-30
“
“
“
30-35
“
“
“
35-40
“
“
“
40-45
“
“
“
THE ABOVE REPRESENT THE TIMES REQUIRED TO TRAVEL IN
RUSH HOURS FROM QUEEN & STREES TO VARIOUS SECTIONS
OF THE CITY BY SUBWAY, STREET CAR & BUS.
WALKING TIME TO NEAREST SUBWAY STATION, CAR OR BUS
STOP IS INCLUDED.
Source: Toronto Transit Commission, 1945
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Spatial Measurement of Transit Service Frequency in Canada
Figure 4: Walking and driving catchments around proposed rapid transit stations, 1973
Source: Ottawa-Carleton, 1973
These
by
using straight line buffers which can be less
transportation infrastructure planners working
complicated, in comparison to using network
for government agencies seeking to increase
buffers (e.g. Guerra et al 2012; Gutiërrez and
mobility and accessibility through transit. More
García-Palomares 2008). Based on these more
recently, academic researchers have begun
accurate catchment areas and the availability
using GIS software to analyse problems of a
of more data on the built environment and
more theoretical (and often critical) nature.
residential populations located within those
Many researchers have sought to distinguish
areas, some planners and researchers have
more accurate measures of catchment areas
built mathematical models referred to as
and to test the differences found between
“direct ridership models” to estimate transit
36
techniques
were
developed
JOURNEYS | November 2014
Spatial Measurement of Transit Service Frequency in Canada
ridership at the station level. These models
different studies in different years couldn’t
provide more accurate ridership forecasts, or
be compared. In order to accurately compare
to more precisely specify the personal and
areas, similarly sized spatial units would have
built environment characteristics that influence
been required. Without them, study results
transit
researchers
suffer from the modifiable areal unit problem
have begun to look into whether publicly-
through which variation in the shape and size
provided transit is being used equitably to
of spatial units produce different results.
ridership.
Also,
some
help people with less income in industrial and
post-industrial societies with large, and often
As a method of analysis was developed to study
growing, income inequalities.
Vancouver’s transit service changes over time,
the potential to apply the method in another
… mathematical models referred
to as “direct ridership models” …
provide more accurate ridership
forecasts, or to more precisely
specify the personal and built
environment characteristics that
influence transit ridership.
Canadian context arose in Ottawa. After many
years of running one of the world’s most
successful Bus Rapid Transit (BRT) systems, the
City of Ottawa embarked on the conversion
of one BRT line to Light Rail Transit (LRT). The
main rationale was that the downtown, where
many BRT lines converged, was bus-saturated
at many times of day. The question of how
The initial motivation for this study was
spatially intensive bus services had become,
to know more about how transit service
just before conversion to LRT began seemed
levels, particularly scheduled departures, had
to be another opportunity. The measurement
changed in Vancouver, Canada’s third most
of the spatial distribution of transit frequency
populace metropolitan area. Since the 1980s,
could be used to establish what that level was
a coordinated effort was made to make the
for the purposes of planning rapid transit in
built form and transport of Vancouver more
other cities.
transit-oriented. During that period, non-rapid
bus services were augmented by rail rapid
A review of the literature and planning studies
transit, commuter rail, and semi-rapid buses.
revealed that some researchers have begun
attaching transit frequencies to the catchment
Different techniques, such as those employed
areas in order to provide a continuous and
in the aforementioned 1928 and 2009 studies,
more representative measure of transit service
had been applied to assess transit coverage
(e.g. Bertolaccini and Lownes 2013). However,
in the past. However, the frequency of transit
the use of different sizes of catchment areas
service, a key dimension, was missing. In
means that it’s difficult to compare intensities
addition, the use of different techniques to
between places within the metropolitan area,
measure service areas meant that results from
or changes over time. In order to overcome
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Spatial Measurement of Transit Service Frequency in Canada
the modifiable area unit problem (variable
(GTFS), the time categories still vary between
spatial units change the level of concentration
jurisdictions. An accurate comparison requires
or density), a relatively fine grid of cells was
accurate data for similar time periods.
used. In the sections that follow, the method
of analysis is described, followed by a brief
A 2011 digital map was created by drawing
summary of results.
the route lines in the program ArcView using
... attaching transit frequencies
to the catchment areas …
provide a continuous and more
representative
measure
of
transit service. However, the use
of different sizes of catchment
areas means that it’s difficult
to compare intensities between
places … or changes over time.
a commercially-produced street map and bus
route maps downloaded in PDF format from
Vancouver’s regional transport authority and
a municipally-owned and operated system
operating routes serving one suburb. While it
would have been possible to obtain the 2011
location of bus stops, the location of bus stops
in previous years would have been unknown,
so the bus routes were drawn as lines. Also,
most local bus services stop frequently enough
that virtually all of the line will be within a
Method
walking catchment. Because the locations of
While Vancouver’s bus stops, rail and ferry
ferry terminals and railway stations were fixed
stations, route and timetable information are
and easily identified, these were drawn as
all now available in electronic format, past
points. The digital files in ArcView were then
routes and schedules existed only on paper
modified to create a set of lines representing
timetables or the scheduling sheets and
the 1981 bus routes, which were taken from
documents of transit operators. Fortunately,
the paper timetables from that year. Often bus
Vancouver’s public bus operator archived old
routes followed different routes at different
schedules and provided full sets of all bus
times of the day, so in numerous cases multiple
timetables from the census years 1981, 1991,
lines were created to represent each different
and 2001. The timetable for the most recent
section. Frequency data was taken from the
study year, 2011, was obtained by downloading
timetables and entered into a spreadsheet
PDF timetables from the operator’s website.
program using the same time of day categories
The number of services on each route was
in all years. The frequency data was attached
recorded by four weekday time periods (6:00-
to the line segments.
9:00, 9:00-15:00, 15:00-18:00, 18:00-24:00),
one period on Saturday (6:00-24:00) and one
In the Ottawa case, we were only concerned
period on Sunday (8:00-24:00). While many
with the year in which we collected the data, so
transit operators now upload their timetable
the process was easier. We simply downloaded
data in the Google Transit Specification Feed
timetables available online from the two major
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Spatial Measurement of Transit Service Frequency in Canada
operators of transit in the metropolitan area.
were later excluded from the analysis on the
While relatively uncomplicated (particularly
basis that the numbers would be insignificant
because there are only two transit operators
to the overall results.
serving the region), the assembly of data
required a large amount of time to create
Once the transit lines and stops had been
points (representing BRT and LRT stops) and
digitised, buffers were drawn around the
lines (representing regular bus routes). The
points and lines with the goal of representing
number of route permutations turned out to
the catchment area which could be accessed by
be much higher than anticipated at the outset
foot. Based on a process of trial and error in order
of the study. Many buses begin on regular
to achieve a reasonably accurate representation
routes with frequent stops and then transfer
of areas served by rapid transit in Vancouver,
to the Transitway bus-only lane, and then
buffers of 300 metres were used for bus lines,
return to regular routes. Approximately 500
500 metres for semi rapid bus stops, and 700
one-way bus segments (representing different
metres for rail rapid transit stations and ferry
route configurations) were identified and
terminals. In the Ottawa study we created a
drawn based on the online versions of the two
700 metres straight line buffer around each of
operators’ timetables published in 2012. These
the points representing 47 Transitway stations
were drawn using the programs Google Maps
and existing LRT stations, and a 300 metres
and ArcGIS version 10.1. Bus routes which
straight line buffer was created around each
followed freeways or Transitway sections
of the lines representing non-Transitway buses.
with limited or no stops were removed and
The latter buffer covered both regular buses
assigned to the single points representing the
and Transitway buses using non-Transitway
Transitway stations. The logic behind removing
roads. These buffers were slightly smaller than
these segments of fast, non-stopping bus
the typical 800 metres for rapid transit station
route segments is that all of the positive and
and 400 metres for a bus line because in the
many of the negative impacts on surrounding
following step a grid was placed over top and
area are associated with stopping and starting.
the values from the buffer touching the grid
While there were still buses passing through
cells were summed up in the grid cells. This
these areas, because some of the negative
created a further increase to the spatial area
(and positive) effects associated with those
in places.
buses are associated with the actual stopping
of the vehicles, and along faster sections
The last step was to create a shapefile overlay
they would have been passing very quickly
grid of 400 metres by 400 metres rectilinear
often through open land without surrounding
polygons using the Fishnet-Grid tool in ArcGIS.
buildings, they were removed. In addition, bus
This overlay was favored over raster information
lines with less than 5 services on any one day
due to the difficulty of associating the buffer
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Spatial Measurement of Transit Service Frequency in Canada
data with the raster and limitations in ArcGIS’s
of transit service. However, there were some
Polygon to Raster tool, which is only capable
areas that experienced declines, in some cases
of associating each raster pixel with one
in areas adjacent to rapid transit routes where
dominant polygon feature. Due to the layering
bus services were likely consolidated. The
of polygons in the final buffer shapefile, the
highest growth in transit service frequency
raster would have been inaccurate as only one
was concentrated in the corridors served
of many layered polygons would be selected.
by rail rapid transit, and by semi-rapid buses
All of the data existing in layered polygons was
using regular city streets but with limited
summarized into each grid square that they
stops, high capacities, and rear-door boarding.
intersected. Finally, some cleanup was required
One particularly interesting finding was that
to remove values which “jumped” bodies of
locations that experienced high gains in
water. The average number of services per
transit service frequency were those served
hour based on all weekly service hours was
by the rapid or semi-rapid transit. However,
calculated and the then mapped, together
there were designated ‘regional centers’ that
with the location of 13 planned LRT stations.
did not experience large gains if they did not
have the rapid or semi-rapid transit, and there
When cells came in contact with a buffer
were places that were not identified in land
representing catchment area, the value of
use plans as important centres which actually
transit service from that buffer was added to
experienced major gains. It suggests that
the cell. As a result, there are some places
places that there has been some disconnection
where the corner of a grid cell would just touch
between the location of places identified as
a buffer and the value would be assigned
metropolitan sub-centres for concentrated
meaning that the value from a bus line could
development and the location of new transit
have extended for over 700 metres in some
infrastructure.
places, although in other places the influence
would not have extended beyond 300 metres
in the case of bus lines.
Results
The results of the study on Vancouver
revealed that over a 30 year period of transit
infrastructure expansion, most of the area had
experienced growth in terms of the frequency
40
The
highest
growth
in
transit service frequency was
concentrated in the corridors
served by rail rapid transit,
and by semi-rapid buses using
regular city streets but with
limited stops, high capacities,
and rear-door boarding.
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Spatial Measurement of Transit Service Frequency in Canada
Figure 5: Cumulative transit service changes in Vancouver, 1981-2011
The results of the Ottawa study showed that
outside of the downtown core the LRT route
in 2012, the year before conversion of a BRT
corresponded with one Transitway corridor,
line to LRT began, transit service was highly
another which could also be a potential LRT
concentrated in a small area, including the
corridor was also clearly visible.
downtown core. The values of the intensity of
transit service were extracted from the GIS and
The analysis was carried out for both all hours
displayed in Table 1. The value of the highest
and only peak travel hours, and maps and data
service category was 257 or more services per
were produced. The same general pattern
hour (greater than four vehicle passages per
holds for both maps, although as expected
minute). The results of the quantification are
the area covered by the highest level of transit
consistent with the rationale for converting
vehicle passages is higher when only peak
BRT to LRT infrastructure in Ottawa. While
hours are considered. The results by category
are presented in Table 1, for all service hours.
Table 1: Service frequency by area units, all hours
The numbers reveal that the area covered by a
Services Per Hour
Area
Share of Total
value that could be considered bus-saturated
>0-32
3,160 km2
87.3%
is quite small, amounting to only 1.4%, and
33-64
185 km2
5.1%
65-128
138 km2
3.8%
most of this is located in Ottawa’s downtown,
129-256
86 km2
2.4%
although a small cluster of high intensity cells
257 or more
52 km
1.4%
appears around two Transitway stations to the
All
3,621 km2
100.0%
southeast of downtown Ottawa.
2
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Spatial Measurement of Transit Service Frequency in Canada
Figure 6: Transit service frequency in Ottawa, 2012
Conclusion
proved incompatible across administrative
This brief summary of the results of two studies
jurisdictions. This type of research is likely to
demonstrates the potential for the measurement
become easier as all transit supply information
of transit frequency across metropolitan areas.
will exist in digital format. But by stepping
Transport planning practitioners rarely carry out
back and looking across regions, or over time,
this kind of small scale or historical research
spatial patterns in one type of transport activity
and these projects provided some evidence
(the frequency of transit vehicle departures)
why. Large amounts of time were used for the
become apparent to the eye, and provide data
digitisation of routes that were not digitised
that can be used to answer many questions.
before, or which were digitised in ways which
Acknowledgement
Some of this research was funded by a Social Sciences and Humanities Research Council (SSHRC)
institutional grant to Concordia University. Numerous Concordia University students assisted with the
data collection and entry. Special thanks go to Juan Buzzetti, Tristan Cherry, Jeff Hignett, and Giannina
Niezen-Coello for their work in the digitization of bus routes. Most of the GIS analysis on Vancouver
was carried out by Donny Seto, and most of the GIS analysis on Ottawa was carried out by Ian Cantello.
Thanks also to Ian Fisher at TransLink and Ian Graham at BC Rapid Transit Co. Ltd. for providing guidance
on counting the frequencies of SkyTrain departures.
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Spatial Measurement of Transit Service Frequency in Canada
References
Bartholomew and Associates. 1928. A Plan for the
City of Vancouver British Columbia. Vancouver:
Town Planning Commission.
Bertolaccini, K. and Lownes, N.E. 2013. Effects of
Scale and Boundary Selection in Assessing Equity of
Transit Supply Distribution, Transportation Research
Record: Journal of the Transportation Research
Board, 2350: pp. 58–64.
Fisher, Ian, Scherr, Wolgang, and Lew, Kean. 2009.
Planning of Vancouver’s Transit Network with an
Operations-Based Model. Presentation at 2009 ITE
Quad Conference, Vancouver, 1 May.
Gutierrez, J. and Garcia-Palomares, J. C. 2008.
Distance-measure impacts on the calculation of
transport services areas using GIS. Environment and
Planning B: Planning and Design, 35: 480-503.
Ottawa-Carleton. 1973. Rapid Transit: A Preliminary
Report. Report No. 3: Transportation Study.
Regional Municipality of Ottawa-Carleton.
Toronto Transit Commission. 1945. Rapid Transit for
Toronto. Toronto, Canada: Toronto Transportation
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Guerra, E., Cervero, R. and Tischler, D. 2012. HalfMile Circle: Does It Best Represent Transit Station
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Craig Townsend is an Associate Professor in the Department of
Geography, Planning and Environment at Concordia University in
Montreal, Canada. His research interests include the spatial intensity
of public transit service, the user costs of private operation of mass
rapid transit systems in Bangkok, post-rail rapid transit restructuring of
Vancouver, variation in high speed transport provision and population
densities between North America’s metropolitan areas, and the history
of bus rapid transit policy.
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