Unit 5: Staff & Fleet Scheduling
Frequency Determination
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Service Planning Steps
Network design
Route design and stop layout
Frequency determination
Timetabling
Vehicle scheduling
Crew scheduling
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Agenda
• Understand the importance of varying route
frequencies
• Discuss different approaches for determining
frequencies
• Calculate demand-based frequencies
• Displaying variable frequencies in maps and
signage
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Frequency Determination
… is how often a vehicle will come by any given
transit stop on a route
… also known as “headways”
… is critical to ensuring
cost-effective, efficient service
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Frequencies are Variable
• Vary by route, time of day,
day of week, day type
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Many Types of Service
•
•
•
•
•
Express Bus
Priority Service
Local
Feeder
Circular
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Varying Frequencies is Useful
It allows us to…
• Identify important routes
• Create system hierarchy
• Improve flow between areas
• Facilitate rider understanding
• Support different trip purposes
• Maintain a cost-effective system
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Why can’t we make every
route very frequent?
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Balancing Cost and Frequency
• It would be great to have fast/ frequent
service on every route, but it would result in:
– Many buses and drivers
– Empty vehicles
– High operating costs
– Roadway congestion
• So how do we figure out the best frequency to
use?
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Three Main Approaches
• Policy-based Frequencies
– Service meeting fed/state mandates
• Performance-based frequencies
– Service meeting fed/state objectives
• Demand-based Frequencies
– Service meeting ridership needs
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Policy-based Frequencies
• Often decided by
– Experience
– Judgment
– Simple passenger counts
• General standards (minutes)
– 15 to 20 – peak, high frequency
– 20 to 60 – off peak, low frequency
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Policy-based Frequencies
• Consistent and fixed intervals between
vehicles on the route
– all day, every day
• Best in areas with low passenger demand
• Most likely clock intervals
– Repeating at set 10, 15, 20 minutes
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Performance-based Frequencies
• Fixed to be goal oriented
• Based on targeted performance standards
over a given service day
• Typically measure non-transit characteristics
OR are determined by optimization
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
MAP-21 Transit Performance
• All about optimization!!
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Demand-based Frequencies
• Most commonly used approach
• Service provided is directly related to
– the number of passengers riding at a given time
– the vehicle capacity required to carry them
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Demand-based Frequencies
• Best in areas where the demand varies
throughout the day
• Meet demand subject to constraints including
peak loading, policy headways and
productivity
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Demand-based Techniques
• Three main calculations used to determine
this frequency
• Practitioners do all 3, pick the best
• Based on
– Point Check Counts
– Ride Check Counts
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Collecting Point Check Data
• Team of trained engineers & planners
– One at each stop location on the route
• Usually known busiest route
– Decide on set time periods
– Record number of riders seen at each stop
location
– Usually completed several times a year
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Example
Average Observed Load by Hour
Stop
Number
Distance to
Next Stop
6-7am
7-8am
8-9am
9-10am
10-11am
Total
Passengers
1
2 mi
50
136
245
250
95
776
2
1 mi
100
510
310
208
122
1250
3
1.5 mi
400
420
400
320
200
1740
4
3 mi
135
335
350
166
220
1206
5
2.5 mi
32
210
300
78
105
725
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 1 (Point Check)
Frequency =
Volume at the Daily Max Load Point
Desired Occupancy
Identifies headways that provide the best
service to the one stop that is busiest over
the entire day
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 1 Data
Average Observed Load by Hour
Stop
Number
Distance to
Next Stop
6-7am
7-8am
8-9am
9-10am
10-11am
Total
Passengers
1
2 mi
50
136
245
250
95
776
2
1 mi
100
510
310
208
122
1250
3
1.5 mi
400
420
400
320
200
1740
4
3 mi
135
335
350
166
220
1206
5
2.5 mi
32
210
300
78
105
725
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 1 Frequencies
Period
Calculation
Frequency
(veh/hr)
Headway
(minutes)
6-7am
400 observed passengers / 50 person capacity
8.0
7.5
7-8am
420 observed passengers / 50 person capacity
8.4
7
8-9am
400 observed passengers / 50 person capacity
8.0
7.5
9-10am
320 observed passengers / 50 person capacity
6.4
9
10-11am
200 observed passengers / 50 person capacity
4.0
15
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Method 2 (Point Check)
Frequency =
Volume at the Hourly Max Load Point
Desired Vehicle Occupancy
Identifies headways that
provide the best service to
specific stops that are
busiest during each time period
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 2 Data
Average Observed Load by Hour
Stop
Number
Distance to
Next Stop
6-7am
7-8am
8-9am
9-10am
10-11am
Total
Passengers
1
2 mi
50
136
245
250
95
776
2
1 mi
100
510
310
208
122
1250
3
1.5 mi
400
420
400
320
200
1740
4
3 mi
135
335
350
166
220
1206
5
2.5 mi
32
210
300
78
105
725
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 2 Frequencies
Frequency Headway
(veh/hr) (minutes)
Period
Calculation
6-7am
400 observed passengers / 50 person capacity
8.0
7.5
7-8am
510 observed passengers / 50 person capacity
10.2
6
8-9am
400 observed passengers / 50 person capacity
8.0
7.5
9-10am
320 observed passengers / 50 person capacity
6.4
9
10-11am
220 observed passengers / 50 person capacity
4.4
14
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Collecting Ride Check Data
• Automatic Passenger Counters (APCs)
– Onboard every route
– Decide on set time periods
– Record number of riders boarding and alighting at
each stop location
– Tells us load variability across a route
– Usually completed several times a year
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Example
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Method 3 (Ride Check)
Frequency =
MAX of…
Passenger Load Space (Passenger-km)___
Desired Vehicle Occupancy x Route Length (km)
OR
Volume at Hourly Max Load Point
Vehicle Capacity
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 3 (Ride Check)
Identifies headways that
minimize the load variability across an entire
route
during the busiest time period
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Method 3 Data
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Method 3 Frequencies
For 6-7am:
Area in passenger-km: (50*2+100*1+400*1.5+135*3+32*2.5)=1285
Desired vehicle occupancy: 50 passengers
Route Length: 10km
Volume at Hourly Max Load Point: 400 passengers (from table before)
Vehicle Capacity: 90 passengers (given)
Option 1: 1285 / (50*10) = 2.57
Option 2: 400 / 90 = 4.44
Pick the larger: 4.44 vehicles/hour
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 3 Data
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Class Exercise
For 8-9am: refer to diagram
Area in passenger-km:
Desired vehicle occupancy:
Route Length:
Volume at Hourly Max Load Point:
Vehicle Capacity:
Option 1:
Option 2:
Pick the larger:
vehicles/hour
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Method 3 Frequencies
Period
Frequency
(veh/hr)
Headway
(minutes)
6-7am
4.44
14
7-8am
5.88
10
8-9am
6.40
9
9-10am
3.72
16
10-11am
3.07
20
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
So Which Method is Better?
• Which is more important?
• Peak day…
Method 1
• Peak hours…
Method 2
• Route variability… Method 3
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
A Note on Finishing Calculations
• Headways should always be rounded down to
the next minute
• If clock headways, round to appropriate
minute on schedule
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Displaying Frequencies
• Most transit maps
highlight routes
• Do not designate
differences between
them
• Is this a concern?
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Display Concerns
• Yes! Not all routes are equal
• It shows us anticipated speeds, wait times,
service times
• Emphasizes network aspect of the transit
system
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Displaying routes
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Frequency Map
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Conclusion
• Routes must vary in frequency.
• There are 3 main approaches for coming up
with these frequencies.
• Demand-based frequencies rely on capacity
and ridership data.
• Frequencies need to be displayed.
Materials developed by K. Watkins, J. LaMondia and C. Brakewood
Reference
Materials in this lecture were taken from:
• Mark Hickman, Fundamentals of Transportation
wikibook, “Network Design & Frequency”,
http://en.wikibooks.org/wiki/Fundamentals_of
_Transportation/Network_Design_and_Frequen
cy
• Chapter 8 of the TCRP “Transit Capacity and
Quality of Service Manual, 3rd edition”, 2013.
Materials developed by K. Watkins, J. LaMondia and C. Brakewood